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Professor Matt Phillips

Biography

Matthew Phillips is Professor of Applied Physics at UTS. He was appointed as Director of the Microstructural Analysis Unit in 1996 and was Associate Head (Research) of the Department of Physics and Advanced Materials since 2006 - 2011. Professor Phillips was awarded a PhD degree from UTS in experimental solid state physics in 1991 for his work on the optical properties of native point defects and transition metals in single crystal sapphire. In 1992 he received the Cowley-Moodie award from the Australian Microscopy and Microanalysis Society.

Dr Phillips has served as Deputy Director of the UTS Centre of Materials Technology (1998 to 2000) and as Research Program Leader in the Institute for Nanoscale Technology (2002 to 2008). Professor Phillips was the Foundation Director of the UTS core research strength, Materials and Technology for Energy Efficiency (2010-2012). He was a Visiting Research Fellow at the University of Sydney in 1996, a Visiting Professor at the Université de Sherbrooke, Quebec in 2005 and a Visiting Professor at the Institute of Solid State Physics at the Technical University of Berlin in 2013. Professor Phillips is currently a member of the International Advisory Board for the Thai National Nanotechnology Center (NANOTEC).

Professor Phillips' research expertise is in materials physics, particularly in the use of novel microscopy based experimental techniques to investigate the opto-electronic properties of technologically important light-emitting materials and nanostructures. ARC Field of Research: Materials Engineering, Nanotechnology and Condensed Matter Physics. Professor Phillips has presented over 30 invited conference papers at international conferences as well as over 35 seminars in overseas laboratories and has co-authored over 260 peer reviewed publications as well as over 220 conference papers.

Professional

Invited Speaker at International Conferences (since 2004)

  1. Photonics West, Oxide-based Materials and Devices Conference OE108, San Francisco, 1 - 6 February, 2014
  2. Fall European Materials Research Society, Warsaw, Symposium F, Novel materials for electronic, optoelectronic, photovoltaic and energy saving applications, 16 - 20 September, 2013
  3. International Conference on Defects - Recognition, Imaging and Physics in Semiconductors (DRIP XV), Poland, 15 - 19 September, 2013
  4. Fall Materials Research Society, Boston, 25-30 Nov 2012, Symposium FF: Semiconductor Nanowires
  5. Fall Materials Research Society, Boston, 25-30 Nov. 2012, Symposium Z: Oxide Semiconductors
  6. New Frontiers in Advanced Functional Nanomaterials, Bangkok, October 2012
  7. Beam Induced Assessment of Microstructures in Semiconductors, 25-28 June Anabas Algeria, 2012
  8. 2nd International Congress in Advances in Applied Physics and Materials Science, 26 - 29 April 2012 Antalya, Turkey
  9. ACEM22/ICONN, 5-9 February Perth, 2012
  10. International Conference on Materials for Renewable Energy and Efficiency, Shanghai, China, 20-22 May, 2011
  11. European Materials Research Society, Fall Meeting, Warsaw, 2011
  12. Conference of the International Union of Microbeam Analysis Societies, Seoul, Korea, 2011
  13. European Materials Research Society, Fall Meeting, Warsaw, 2009
  14. Microscopy & Microanalysis, Annual Conference of the Microscopy Society, Richmond, USA, 2009
  15. 9th Asia-Pacific Microscopy Conference, ICC Jeju, Jeju Island, Korea, 2008
  16. Microscopy & Microanalysis, Annual Conference of the Microscopy Society, Chicago, USA, 2006
  17. Microscopy & Microanalysis, Annual Conference of the Microscopy Society, Honolulu, USA, 2005
  18. Conference of the International Union of Microbeam Analysis Societies, Florence, Italy 2005
  19. European Materials Research Society, Fall meeting, Warsaw, Poland, 2004
  20. Royal Microscopical Society, MicroScience, London, UK, 2004
  21. Microscopy & Microanalysis, Annual Conference of the Microscopy Society, Savannah, USA, 2004

Professional Seminars (since 2009)

  1. University of Magdeburg, Das Institut für Experimentelle Physik, June, 2013
  2. National Nanotechnology Center (NANOTEC), Pathumthani Thailand, 20 February 2013
  3. MINATEC, Grenoble, France, 17 September 2012
  4. Mahidol University, Bangkok,Thailand, 21 March 2012
  5. King Mongkut’s University of Technology Thonburi (KMUTT), Thailand, 20 June 2011
  6. Mahidol University Bangkok, Thailand, 21 June 2011
  7. National Nanotechnology Center (NANOTEC), Pathumthani, Thailand, 21 June 2011
  8. Rajabhat University (PSRU), Pibulsongkram, Thailand, 22 June 2011
  9. Naresuan University, Pibulsongkram, Thailand, 22 June 2011
  10. Thammasat University, Patumtani, Thailand, 23 June 2011
  11. Public Seminar for the Thailand Environment Institute (TEI), Bangkok, Thailand, 24 June 2011
  12. Chulalongkorn University, Bangkok, Thailand, 24 June 2011
  13. Department of Physics, Nanjing University, China, October, 2011
  14. UTS Speaks, Public Lecture, UTS, November 2010
  15. German Centre of Excellence for Semiconductor Nanophotonics, TU-Berlin, June, 2009

Conference and Symposium Organiser (since 2010)

  1. 6th Forum on New Materials, Symposium Co-Chair, Materials and Technologies for Solid State Lighting, , Montecantini Terme, Italy, 8-20 June 2014
  2. European Materials Research Society, Symposium Co-Chair, Nitride Semiconductors, Strasbourg, France, 27 - 31 May, 2013
  3. Conference Chair, Australian Microbeam Analysis Society Symposium and Workshops, XII, Sydney, 4 - 8, February 2013
  4. Scientific Committee, 11th International Workshop on Beam Injection Assessment of Microstructures in Semiconductors, 23-28th June, Annaba, Algeria, 2012
  5. Symposium Chair, Advances in Cathodoluminescence, International Union of Microbeam Analysis Societies, Seoul, Korea, 2011
  6. Scientific Committee, 10th International Workshop on Beam Injection Assessment of Microstructures in Semiconductors, 4th – 8th July, Halle, Germany, 2010
  7. Symposium Chair: "Scanning Cathodoluminescence Spectroscopy and Microanalysis, Microscopy and Microanalysis 2010, Portland, Oregon, August, 2010

Professional Societies

  • Materials Research Society
  • Australian Microscopy and Microanalysis Society
  • Microbeam Analysis Society
  • ARC Nanotechnology Network
  • ARC Australian Network for the Fluorescence Applications in Biotechnology and the Life Sciences
Image of Matt Phillips
Professor, School of Mathematical and Physical Sciences
Member, Research Centre for Clean Energy Technology
Core Member, Research Strength Materials and Technology for Energy Efficiency Member
Professor, Faculty of Science
Member, Research Centre for Clean Energy Technology
Core Member, Research Strength Materials and Technology for Energy Efficiency Member
BSc (UNSW), PhD (UTS)
 
Phone
+61 2 9514 1620
Room
CB04.04.56C

Research Interests

Professor Phillips and his group conduct research on the light emitting properties of bulk and nano-structured technologically important materials, in particular group III-nitrides and binary oxide semiconductors. Experimental methods include; scanning cathodoluminescence microscopy and spectroscopy, in-situ variable pressure SEM, scanning tunnelling microscopy and spectroscopy, UV laser photoluminescence spectroscopy, deep level transient spectroscopy and a broad range of associated materials microcharacterisation and fabrication techniques. ( www.sydneynano.com )

Specific research interests involve:

  1. optical and electrical properties of point defects in semiconducting nitrides and oxides.
  2. luminescence mechanisms in nanowires and nano-particles.
  3. light emitting low dimensional semiconductor structures, quantum wells, wires and dots.
  4. physics and chemistry of super-luminescence ceramic and semiconductor phosphors.
  5. transport dynamics of polarons, excitons and polaritons in semiconductors.
  6. in-situ studies of nano-wires during growth using variable pressure electron microscopy.
  7. light-matter interactions in spatially confined systems.
  8. light extraction using photon - surface plasmon coupling.
  9. direct-write resist-free nano-lithography using focussed electron beam induced deposition and etching.
  10. application of this work to the development of high performance solid state lighting devices, advanced light and electron detectors as well as innovative bio-imaging platform technologies.
Can supervise: Yes

Current Postgraduate Students

1.  Toby Shanley, PhD principal supervisor, 2012
2.  Liangchen Zhu, PhD, co- supervisor, 2011
3.  Suranan Anantachaisilip, PhD, principal supervisor, 2011
4.  Joel Davis, MSc, principal supervisor, 2011
5.  Gordon Callsen, PhD, principal supervisor, co-tutelle TU Berlin, 2010
6.  Christian Nenstiel, PhD, principal supervisor, co-tutelle TU Berlin, 2010
7.  Mark Lockrey, principal supervisor, 2010

Completed PhD and MSc Theses

1.   PhD (2013), Marcus Straw (2013) principal supervisor
2.   PhD (2013) Olivier Lee, co-supervisor
3.   MSc (2012), James Bishop, MSc, principal supervisor
4.   PhD (2010) Matthew Foley, PhD, 2007, co-supervisor
5.   PhD (2008) Enno Malguth, IPRS, principal supervisor
6.   PhD (2007) Rachel White, APA, principal supervisor
7.   PhD (2007) Sudha Mokkapati, supervisory committee ANU
8.   PhD (2006) Scott Morgan, APA, principal supervisor
9.   PhD (2006) Victoria Coleman, supervisory committee ANU
10. PhD (2005) Stephan Schelm, co-supervisor
11. PhD (2005) Carl Masens, co-supervisor
12. PhD (2004) Olaf Gelhausen, IPRS, principal supervisor
13. PhD (2001) Richard Wuhrer, co-supervisor
14. PhD (2000) Milos Toth, APA, principal supervisor
15. PhD (1999) Svetlana Dglitach, co-supervisor
16. MSc (1998) Lisa Emerson, principal supervisor

Exchange StudentsTechnische Universitäet Berlin Exchange Students:

Karsten Fleischer (1999), Olaf Gelhausen (2000), Hagen Telg (2001), Holger Klein (2002), Nicolas Pomplum (2003), Enno Malguth (2003), Markus Wagner (2004), Christian Rauch (2005), Gordon Callsen (2007), Jurgen Probst (2007), Daniela Neuman (2008), Bruno Riemenschneider (2008), Dorian Alden (2009), Nadja Jankowski (2012), Sarah Schlichting (2012)

Other Exchange Students:

Zuzana Majlinova, Slovak University of Technology, Bratislava (2003); Moritz Merklein, University of Konstanz (2010) and May Patropon, Mahidol University, Thailand (2011)

Current Subjects:

  • Solid State and Nano-device Physics 68606
  • Scanning Probe and Electron Microscopy 68320
  • Physics & Nanotechnology Honours Course Work 68861

Past Subjects:

  • Techniques of Materials Analysis 68516
  • Electron Microscopy and Microanalysis 60502
  • Scanning Probe Microscopy 60503
  • X-ray Diffraction Techniques 60501
  • Forensic Imaging 65341
  • Nanoscience 1 60103
  • Nanoscience 2 60104

Chapters

Remond, G., Phillips, M. & Roques-Carmes, C. 2000, 'Importance of Instrumental Factors on the Reliability of Cathodoluminescence Data' in Pagel, M., Barbin, V., Blanc, P. & Ohnenstetter, D. (eds), Cathodoluminescence in Geosciences, Springer-Verlag, Berlin, Germany, pp. 59-126.
Kalceff, M.A.S., Phillips, M.R., Moon, A.R. & Kalceff, W. 2000, 'Cathodoluminescence microcharacterisation of silicon dioxide polymorphs', SPRINGER-VERLAG BERLIN, pp. 193-224.

Conferences

Phillips, M., Manning, T.J., Nenstiel, C., Lockrey, M.N., Ton-That, C. & Hoffmann, A.V. 2011, 'High Temperature In-Situ Cathodoluminescence Studies of the Thermal Stability of Hydrogen in p-type Magnesium Doped Gallium Nitride', Microscopy and Microanalysis, Vol 17, Supplement 2, High Temperature In-Situ Cathodoluminescence Studies of the Thermal Stability of Hydrogen in p-type, Nashville, Tennessee, pp. 1-2.
Manning, T.J., Hardy, T., Merklein, M., Wintrebert-Fouquet, M. & Phillips, M.R. 2010, 'A Mechanism for Mg acceptor activation in GaN by Low Energy Electron Beam Irradiation', Conference on Optoelectronic and Microelectronic Materials and Devices, Proceedings, COMMAD, pp. 139-140.
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Low Energy Electron Beam Irradiation (LEEBI) was found to quench the donor-acceptor pair (DAP) attributed to carbon (CN at 3.28 eV at 80 K) and enhances the emission of the 3.27 eV peak, which has been attributed to a free-to-bound (e,Mg0) transition at 300 K. This results in increased cathodoluminescence (CL) emission at room temperature and a decrease in CL emission at liquid nitrogen temperatures (~77 K). © 2010 IEEE.
Nenstiel, C., Nenstiel, C., Switaisky, T., Alic, M., Suski, T., Albecht, M., Phillips, M.R. & Hoffmann, A. 2010, 'Luminescence of InGaN MQWs grown on misorientated GaN substrates', Conference on Optoelectronic and Microelectronic Materials and Devices, Proceedings, COMMAD, pp. 135-136.
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Optoelectronic devices based on InGaN have already been commercialised, however, the Indium content is limited to around 5%. With higher Indium concentration the quantum efficiency decreases, which is thought to be due to increasing inhomogeneity. In this work it is shown that the growth of InGaN on misorientated GaN substrates forces these Indium fluctuations on a nanometre scale. Temperature dependent luminescence measurements provide information about the homogeneity of the band structure. Energy selective excitation confirms the existence of localisation centres and indicates their energetic depth. Time-resolved measurements define the lifetime of localized excitons, which provides information about radiative and nonradiative processes as well as tunnelling mechanisms between the localization centres. Indium fluctuations at the nm and ?m scale are measured using cathodoluminescence (CL) and Micro Photoluminescence (?PL) respectively. © 2010 IEEE.
Foley, M., Ton-That, C. & Phillips, M.R. 2010, 'Cathodoluminescence characterisation of vapour transport grown ZnO structures', ICONN 2010 - Proceedings of the 2010 International Conference on Nanoscience and Nanotechnology, pp. 207-209.
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ZnO structures grown under controlled vapour-phase transport growth conditions were characterised by electron microscopy and high-resolution cathodoluminescence techniques. Variations in the defect related emission and morphology were observed to be dependent on the distance from the source material. Annealing of grown structures under oxygen eliminated the defect emission. These experimental observations suggest that oxygen deficiency in ZnO is linked to the defect related emission, and that defect emission is strongly influenced by the oxygen gas content during vapour transport growth. © 2010 IEEE.
Dowd, A.R., Armstrong, N.G., Ton-That, C., Johansson, B. & Phillips, M. 2008, 'Cathodoluminescence for High Resolution Non-Destructive Luminescence Depth Profiling.', IUMRS-ICEM 2008 | COMMAD 2008, A-MRS, Parkville, VIC.
Coleman, V.A., Bradby, J.E., Jagadish, C. & Phillips, M.R. 2007, 'A comparison of the mechanical properties and the impact of contact induced damage in a- and c- axis ZnO single crystals', Materials Research Society Symposium Proceedings, pp. 213-218.
Nanoindentation studies were conducted on a-axis oriented ZnO single crystals. The mechanical properties and deformation mechanisms were monitored and compared to previously determined data from c-axis material. Hardness and modulus values reveal that a-axis ZnO is significantly softer than c-axis material (hardness of 2 ± 0.2 GPa), and behaves more plastically. Additionally, the influence of contact induced damage on the defect structure of a-axis material was examined using cathodoluminescence spectroscopy and monochromatic imaging to monitor the luminescence from indent sites. Deformation directly under the indent site enhanced the occurrence of red luminescence, and was attributed to a native defect in ZnO that has a higher formation energy than the defects responsible for the green and yellow visible defect bands, which were present in ZnO during growth and clustered to the indent site during annealing. © 2007 Materials Research Society.
Malguth, E., Hoffmann, A.V., Phillips, M. & Gehlhoff, W. 2006, 'Fe-centers in GaN as candidates for spintronics applications', GaN, AlN, InN And Related Materials, Materials Research Society, Warrendale, USA, pp. 131-136.
The potential use of Fe doped GaN for spintronics applications requires a complete understanding of the electronic structure of Fe in all of its charge states. To address these issues, a set of 400 mu m thick freestanding HVPE grown GaN:Fe crystals with
Zareie, H., Sarikaya, M., McDonagh, A.M., Barber, J., Cortie, M. & Phillips, M. 2006, 'Self-organized materials: From organic molecules to genetically engineered gold-binding proteins', Proceedings of the 2006 International Conference on Nanoscience and Nanotechnology, ICONN, pp. 517-519.
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We present examples of ordered assemblies of organic and biological molecules on gold(111) surfaces. The first example shows how control over mono- or multilayer assemblies of 1,4-phenylenedimethanthiol can be achieved and monitored. The second example shows how monolayers on gold can be prepared using amine groups to anchor aromatic molecules to the surface. A third example shows how ordered assemblies of genetically-engineered inorganic-binding polypeptides can be formed on gold surfaces using a 3-repeat, 14 amino acid gold-binding protein (GBP1). © 2006 IEEE.
Phillips, M.R. & Morgan, S.W. 2006, 'Enhanced high speed SE imaging in a VPSEM using a Frisch grid', Microscopy and Microanalysis, pp. 1480-1481.
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Wuhrer, R., Moran, K., Moran, K., Phillips, M.R. & Davey, P. 2006, 'X-ray mapping using a multiple-EDS (DUAL) detectors', Microscopy and Microanalysis, pp. 1406-1407.
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Phillips, M.R. & Drouin, D. 2006, 'Comparison of low voltage cathodoluminescent phosphors', Microscopy and Microanalysis, pp. 1526-1527.
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McBean, K.E., Phillips, M.R. & Drouin, D. 2006, 'Effects of lithium doping and post-processing on the cathodoluminescence of zinc oxide nanoparticles', Microscopy and Microanalysis, pp. 1510-1511.
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Mokhapati, S., Tan, H.H., Jagadish, C., McBean, K.E. & Phillips, M. 2006, 'Integration of quantum dots devices by selective area epitaxy', Proceedings of the 2006 International Conference on Nanoscience and Nanotechnology, IEEE, USA, pp. 442-445.
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The results of nucleation of InGaAs and InAs quantum dots by selective area epitaxy are presented. By pre-patterning the substrates with different (SiO2) mask dimensions the bandgap of the quantum dots can be tuned over a large range. This technique is used to demonstrate a quantum dot lase integrated with a quantum well waveguide.
Drouin, D., Pauc, N., Phillips, M., Poissant, P., Delample, V. & Souifi, A. 2006, 'SEM characterisation of nanodevices and nanomaterials', Proceedings of the 2006 International Conference on Nanosacience and Nanotechnology, IEEE, USA, pp. 596-599.
The scanning electron microsope (SEM) cna be used to study and characterise a wide variety of materials used in nanoelectronic and photonic applications. Several different techniques make use of this versatile tool. These include voltage conrtast in secondary electron imaging, charge colletion for semiconductor samples and cathodoluminescnece. These techniques are important in device nanofabrication process development and nanomaterials characterisation.
Phillips, M., Drouin, D. & Pauc, N. 2006, 'Probing carrier behaviour at the nanoscale in gallium nitride using low voltage cathodoluminescence', Proceedings of Microscopy & Microanalysis 12, Suppl. 2 2006, Cambridge Univesity Press, USA, pp. 156-157.
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The increasing application of GaN in blue and UV light emitting diodes and lasers has generated considerable interest in its optical and electrical properties. These optical devices exhibit extremely high emission efficiencies despite the presence of a very high concentration of threading dislocations (108 1010 cm-2) that act as non-radiative recombination channels. This perceived contradiction can be been explained by small (< 100 nm) carrier diffusion lengths which effectively negate the effect of the threading dislocations on the radiative recombination efficiency. These short exciton and minority carrier diffusion lengths in GaN can be explored by cathodoluminescence (CL) microscopy and spectroscopy using a SEM equipped with a Schottky field emission gun operating at 1 kV.
Wuhrer, R., Moran, K., Moran, K. & Phillips, M.R. 2006, 'X-ray mapping and post processing', Microscopy and Microanalysis, pp. 1404-1405.
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Phillips, M.R., Drouin, D. & Pauc, N. 2006, 'Probing carrier behavior at the nanoscale in gallium nitride using low voltage cathodoluminescence', Microscopy and Microanalysis, pp. 156-157.
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Pauc, N., Phillips, M., Aimez, V. & Drouin, D. 2006, 'Cathodoluminescence study of GaN and GaN:Si on sapphire', Proceedings of SPIE - The International Society for Optical Engineering.
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We present a luminescence study of as-grown GaN and GaN:Si samples by means of low voltage cathodoluminescence (CL) at low temperature. It is shown that high spatial resolution CL microscopy allows direct luminescence mapping of threading dislocations in the doped and undoped samples. Comparison of monochromatic CL images acquired near the band gap energy (free and bound excitons) and at lower energies (recombination on defects) reveal the dopant segregation around dislocations.
Butcher, K.S.A., Ferris, J.M., Phillips, M.R., Wintrebert-Fouquet, M., Jong Wah, J.W., Jovanovic, N., Vyverman, W. & Chepurnov, V.A. 2005, 'A luminescence study of porous diatoms', Materials Science and Engineering C, pp. 658-663.
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The cathodoluminescent and photoluminescent properties of the nanoporous silica frustules of various diatom strains and of natural diatom samples are presented. The spectra are observed to be similar to that of pure silica glass and the phenology is therefore believed to also be somewhat similar. A strong UV-blue luminescence peak is commonly observed as well as a yellow peak at 2.15 eV. For the more heavily silicified field-collected freshwater benthic samples, a strong red peak at 1.95 eV is also observed. The 2.15 eV peak is also more strongly evident for the field-collected samples. The UV-blue peak is related to common silica defect structure but cathodoluminescent microanalysis shows that this emission is highly localized in the diatom samples. &copy; 2005 Elsevier B.V. All rights reserved.
Wuhrer, R., Moran, K., Phillips, M. & Davey, P. 2005, 'X-ray Mapping using Multiple EDS and WDS Detectors', Proceeding Microscopy and Microanalysis Vol 11 (Suppl2), Cambridge University Press, United Kingdom, pp. 1678-1679.
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High quality x-ray mapping (XRM) has been used for over 30 years by experienced wavelength dispersive spectroscopy (WDS) operators. Manufacturers have been developing similar techniques using energy dispersive spectroscopy (EDS) over the last 20 years. This has been generally unsuccssful due to a number of problems such as poor computer specifications, cost, time to map and generally poor peak to bacjground ratios (P:B). With improvements in all the above parameters EDS mapping is now gaining in popularity.
Wuhrer, R., Huggett, P.G., Moran, K., Phillips, M. & Ben-Nissan, B. 2005, 'EBSD and XRM of Phases in Vacuum Cast Composite Alloys', Proceeding Microscopy and Microanalysis Vol 11 (S2), Cambridge University Press, United Kingdom, pp. 1678-1679.
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There have been a number f new processes developed that allow the joining of very dissimilar materials such as titanium alloys, wear resistant white irons, cast irons and ceramic materials to ferrous (mild steel) and non-ferrous (aluminium) alloys. These new processes have allowed the development of more complex composite shapes to be produced. However, with any new process development, an undertsnating of the mechanism of bonding is required. through the use of x-ray mapping (XRM), chemical phase imaging as well as electron back scattered diffraction (EBSD) analsysis, very useful information on the mass transport across the interface as well as phase segregation, texture variations and phase distribution within the bond interface can be obtained. results from this investigation on a number of bonded materials are presented and the importance of XRM and EBSD in providing a better understanding of the physical and chemical processes involved in metallurgical bonding/welding of dissimilar materials discussed.
Phillips, M. & Morgan, S.W. 2005, 'Direct Comparison of Various Gaseous Secondary Electron Detectors in the Variable Pressure Scanning Electron Microscope', Proceeding Microscopy and Microanalysis vol 11 (Suppl 2), Cambridge University Press, United Kingdom, pp. 398-399.
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The conventional Everhart-Thornely scintillation-photomultiplier secondary electron (SE) detector cannot function at elevated pressures due to the high voltage (~ +12kV) involved in its operation. As a result, SE imaging in the variable pressure scanning electron microscope (VPSEM) has required the development of a new generation of SE detectors that operate under low vacuum conditions. To date, three different methods have been devised to measure the secondary electron (SE) emission signal in a VPSEM. Each of these approaches involves the excitation of the chamber gas by the placement of a low voltage (< +1000V) positively biased electrode in the vicinity of the specimen. A SE image can be obtained by measuring the current induced in either the positive electrode (the gaseous secondary electron detector) or the grounded stage (the ion current detector) or via a photomultiplier that detects light emission from the gas (the gas luminescence detector). In this work, the performance of each of these three low vacuum SE detector types has been compared under identical operating conditions using a Zeiss Supra 55VPSEM and FEI XL30 ESEM.
Coleman, V.A., Tan, H.H., Jagadish, C., Kucheyev, S.O., Zou, J. & Phillips, M.R. 2005, 'Towards p-type doping of ZnO by ion implantation', Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, pp. 847-848.
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The thermal stability of ion implanted ZnO was investigated. Heavily damaged ZnO decomposes with thermal treatment. This result has significant implications for ion implants into ZnO for p-type doping, and subsequent thermal treatments for activation. &copy; 2005 IEEE.
Coleman, V.A., Tan, H.H., Jagadish, C., Kucheyev, S.O., Phillips, M.R. & Zou, J. 2005, 'Towards p-type doping of ZnO by ion implantation', Materials Research Society Symposium Proceedings, pp. 361-366.
Zinc oxide is a very attractive material for a range of optoelectronic devices including blue light-emitting diodes and laser diodes. Though n-type doping has been successfully achieved, p-type doing of ZnO is still a challenge that must be overcome before p-n junction devices can be realized. Ion implantation is widely used in the microelectronics industry for selective area doping and device isolation. Understanding damage accumulation and recrystallization processes is important for achieving selective area doping. In this study, As (potential p-type dopant) ion implantation and annealing studies were carried out. ZnO samples were implanted with high dose (1.4 1017 ions/cm2) 300 keV As ions at room temperature. Furnace annealing of samples in the range of 900&deg;C to 1200&deg;C was employed to achieve recrystallization of amorphous layers and electrical activation of the dopant. Rutherford backscattering/channeling spectrometry, transmission electron microscopy and cathodolumiescence spectroscopy were used to monitor damage accumulation and annihilation behavior in ZnO. Results of this study have significant implications for p-type doing of ZnO by ion implantation. &copy; 2005 Materials Research Society.
Wuhrer, R., Moran, K., Huggett, P., Phillips, M.R. & Ben-Nissan, B. 2004, 'X-ray mapping and electron back scattered diffraction of phases in welded materials', Microscopy and Microanalysis, pp. 916-917.
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Wuhrer, R., Phillips, M.R., Mason, K., Roux, C., Maniago, J.R. & Hales, S. 2004, 'GSR analysis in the environmental scanning electron microscope', Microscopy and Microanalysis, pp. 1362-1363.
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White, R., Phillips, M., Thomas, P., Wuhrer, R. & Dredge, P. 2004, 'Interactions between pigments in 19th and early 20th century oil paintings - In situ studies using the environmental scanning electron microscope', Microscopy and Microanalysis, pp. 132-133.
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Gelhausen, O., Malguth, E., Phillips, M., Goldys, E.M., Strassburg, M., Hoffmann, A.V., Graf, T., Gjukic, M. & Stutzmann, M. 2004, 'Optical Properties of Mn -doped GaN', Proceedings MRS Fall Meeting, Materials Research Society, Materials Research Society, Warrendale Pennsylvania, pp. 569-574.
Phillips, M.R. & McBean, K.E. 2004, 'In-situ evaluation of post growth treatments on the cathodoluminescence properties of fluorescent nano-particles in the environmental scanning electron microscope', Microscopy and Microanalysis, pp. 1064-1065.
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Phillips, M.R., Gelhausen, O. & Goldys, E.M. 2004, 'Cathodoluminescence properties of zinc oxide nanoparticles', Physica Status Solidi C: Conferences, pp. 229-234.
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Zinc oxide nano-particles (25 nm) have been investigated by cathodoluminescence spectroscopy (300 nm-1700 nm) at 80 K and 300 K following thermal annealing in high purity H2/N2, N2, O2 and Ar gaseous atmospheres. The intensity of the ZnO near band edge peak was significantly increased after heat treatment in hydrogen. Conversely, thermal annealing in the other gas types decreased this emission. This effect is attributed to hydrogen passivation of competitive non-radiative defect centers, most likely bulk zinc vacancy centers. The appearance of a strong green emission centered at 2.4 eV following thermal annealing in all gas atmospheres is ascribed to the formation of bulk oxygen vacancy defects. A strong red shift of the near band edge emission with increasing beam current at 300 K is accredited to electron beam heating rather than to an increase in the carrier density. Electron beam heating is evidenced by the occurrence of a strong black body emission in the near infrared spectral region. &copy; 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Gelhausen, O., Malguth, E., Malguth, E., Phillips, M.R., Goldys, E.M., Strassburg, M., Strassburg, M., Hoffmann, A., Graf, T., Gjukic, M. & Stutzmann, M. 2003, 'Optical properties of Mn-doped GaN', Materials Research Society Symposium - Proceedings, pp. 569-574.
Molecular beam epitaxy-grown GaN with different Mn concentrations (5-231019 cm-3) and codoped with Si were investigated by cathodoluminescence (CL) spectroscopy and optical transmission measurements. In the GaN:Mn, an intense absorption peak at 1.414 +/- 0.002 eV was observed. This peak was attributed to an internal 5T 2? 5E transition of the deep neutral Mn3+ state since its intensity scaled with the Mn3+ concentration. The CL measurements showed that Mn-doping concentrations around 1020 cm -3 had three effects on the emission spectrum: (i) the donor bound exciton at 3.460 eV was reduced by more than one order of magnitude, (ii) the donor-acceptor-pair band at 3.27 eV was completely quenched and (iii) the yellow luminescence centered at 2.2 eV was the strongly decreased. The latter two effects were attributed to a reduced concentration of VGa. In the infrared spectral range, three broad, Mn-doping related CL emission bands centered at 1.01 &plusmn; 0.02 eV, 1.09 &plusmn; 0.02 eV and 1.25 &plusmn; 0.03 eV were observed. These bands might be related to deep donor complexes, which are generated as a result of the heavy Mn-doping, rather than internal transitions at the Mn atom.
Gelhausen, O., Phillips, M.R., Goldys, E.M., Paskova, T., Monemar, B., Strassburg, M. & Hoffmann, A. 2003, 'Formation and dissociation of hydrogen-related defect centers in Mg-doped GaN', GAN AND RELATED ALLOYS - 2003, MATERIALS RESEARCH SOCIETY, pp. 497-502.
Griffin, B., Suvorova, A. & Phillips, M. 2002, 'A review of gas-electron interactions imaging and X-ray analysis in variable pressure SEM', Proceedings of the 15th International Congress on Electron Microscopy, Microscopy Society of Southern Africa, Onderstepoort, South Africa, pp. 215-216.
Phillips, M. & Morgan, S.W. 2002, 'Time dependent behaviour of positive ions in the variable pressure scanning electron microscope', Proceedings of the 15th International Congress on Electron Microscopy, Microscopy Society of Southern Africa, Onderstepoort, South Africa, pp. 219-220.
Toth, M., Craven, J.P., Phillips, M., Thiel, B.L. & Donald, A.M. 2002, 'X-ray microanalysis of insulators in a variable pressure environment', Proceedings of Microscopy and Microanalysis 2002, Vol 11 (suppl 2), Cambridge University Press, New York, USA, pp. 1478-1479.
Phillips, M.R. & Morgan, S.W. 2002, 'Time resolved analysis of the positive ion dynamics in the variable pressure scanning electron microscope', Microscopy and Microanalysis, pp. 446-447.
Godlewski, M., Ivanov, V., Khachapuridze, A., Narkowicz, R. & Phillips, M. 2001, 'Effects of Localisations in CdTe-Based Quantum Well Structures in optical Organic and Inorganic Materials', Proceedings of the SPIE, SPIE, USA, pp. 86-91.
Phillips, M., Griffin, B., Drouin, D., Nockolds, C. & Remond, G. 2001, 'X-Ray Micronalaysis in the Environmentl SEM Using Mapping and Fourier Deconvolution Techniques', Microscopy & Microanalysis 2001 Proceedings Volume 7 Supplement 2, Springer Verlag, New York, pp. 708-709.
Gross, K.A., Phillips, M.R. & Suetsugu, Y. 2001, 'Cathodoluminescence emission for differentiating the degree of carbonation in apatites', Key Engineering Materials, pp. 179-182.
Cathodoluminescence has recently been used successfully in detecting and determining the spatial location of the amorphous phase in plasma sprayed calcium phosphate coatings. The aim of this study is to determine whether this same technique can be used to detect different carbonate substitutions in apatites. Single crystals were analysed with cathodoluminscence spectroscopy and the results indicated a change in peak shape. The substitution of carbonate into the hydroxyapatite structure creates a more well defined peak with a narrower width at half the peak height.
Morgan, S.W. & Phillips, M. 2001, 'Time Dependent Study of the Positive Ion Current in the Environmental Scanning Electron Microscope (ESEM)', Microscopy & Microanalysis 2001 Proceedings Volume 7 Supplement 2, Springer Verlag, New York, pp. 788-789.
Remond, G., Nockolds, C.E., Phillips, M.R. & Cazaux, J. 2000, 'Charging phenomena of wide bandgap materials in a VP-SEM.', MICROBEAM ANALYSIS 2000, PROCEEDINGS, IOP PUBLISHING LTD, pp. 269-270.
Phillips, M.R. & Toth, M. 2000, 'Charge neutralization of insulators in an ESEM', MICROBEAM ANALYSIS 2000, PROCEEDINGS, IOP PUBLISHING LTD, pp. 273-274.
Toth, M., Phillips, M.R., Kucheyev, S.O., Williams, J.S., Jagadish, C. & Li, G. 2000, 'Charge contrast in SE images obtained using the ESEM', MICROBEAM ANALYSIS 2000, PROCEEDINGS, IOP PUBLISHING LTD, pp. 275-276.
Griffin, B.J., Nockolds, C.E., Phillips, M.R. & Remond, G. 2000, 'New needs for imaging and x-ray microanalysis standards: ESEM, CHIME and low voltage microanalysis', MICROBEAM ANALYSIS 2000, PROCEEDINGS, IOP PUBLISHING LTD, pp. 395-396.
Wuhrer, R., Yeung, W. & Phillips, M.R. 2000, 'SEM/EDS, AFM and XRD analysis of ternary nitride coatings produced by magnetron co-sputtering at different nitrogen pressures', MICROBEAM ANALYSIS 2000, PROCEEDINGS, IOP PUBLISHING LTD, pp. 449-450.
Toth, M., Fleischer, K. & Phillips, M.R. 1999, 'Electron beam induced impurity electro-migration in unintentionally doped GaN', Materials Research Society Symposium - Proceedings, Materials Research Society.
Electron beam induced electromigration of ON+ and H+ impurities in unintentionally n-doped GaN was investigated using cathodoluminescence (CL) kinetics profiling, CL imaging of regions pre-irradiated with a stationary electron beam, and wavelength dispersive x-ray spectrometry (WDS). The presented results (i) illustrate induced impurity diffusion in wide bandgap semiconductors, (ii) provide experimental evidence for the (VGa-ON)2- model of yellow luminescence in GaN with low Si content, (iii) confirm the roles of O in frequently reported bound exciton and donor-acceptor pair emissions and (iv) suggest the involvement of ON+ and hydrogenated gallium vacancies in a blue emission in autodoped GaN.

Journal articles

Choi, S., Phillips, M.R., Aharonovich, I., Pornsuwan, S., Cowie, B.C.C. & Ton-That, C. 2015, 'Photophysics of Point Defects in ZnO Nanoparticles', Advanced Optical Materials.
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Zinc oxide (ZnO) nanoparticles have recently been identified as a promising candidate for advanced nanophotonics applications and quantum technologies. This work reports the formation of luminescent point defects and describes their photophysical properties. In particular, it is shown using correlative photoluminescence, cathodoluminescence, electron paramagnetic resonance (EPR), and X-ray absorption near-edge spectroscopy that green luminescence at 2.48 eV and an EPR line at g = 2.00 belong to a surface oxygen vacancy (Vo,s+) center, while a second green emission at 2.28 eV is associated with zinc vacancy (VZn) centers. It is established that radiative point defects can be excited in the visible that exhibits nanosecond lifetimes using both above bandgap and sub-bandgap 405 and 532 nm excitation. This work provides important knowledge towards employment of point defects in ZnO in nanophotonics technologies.
Choi, S., Berhane, A.M., Gentle, A., Ton-That, C., Phillips, M.R. & Aharonovich, I. 2015, 'Electroluminescence from Localized Defects in Zinc Oxide: Toward Electrically Driven Single Photon Sources at Room Temperature', ACS Applied Materials and Interfaces, vol. 7, no. 10, pp. 5619-5623.
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Single photon sources are required for a wide range of applications in quantum information science, quantum cryptography, and quantum communications. However, the majority of room temperature emitters to date are only excited optically, which limits their proper integration into scalable devices. In this work, we overcome this limitation and present room temperature electrically driven light emission from localized defects in zinc oxide (ZnO) nanoparticles and thin films. The devices emit in the red spectral range and show excellent rectifying behavior. The emission is stable over an extensive period of time, providing an important prerequisite for practical devices. Our results open possibilities for building new ZnO-based quantum integrated devices that incorporate solid-state single photon sources for quantum information technologies. (Graph Presented).
Choi, S., Johnson, B.C., Castelletto, S., Ton-That, C., Phillips, M.R. & Aharonovich, I. 2014, 'Single photon emission from ZnO nanoparticles', Applied Physics Letters, vol. 104, no. 26.
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Room temperature single photon emitters are very important resources for photonics and emerging quantum technologies. In this work, we study single photon emission from defect centers in 20 nm zinc oxide (ZnO) nanoparticles. The emitters exhibit bright broadband fluorescence in the red spectral range centered at 640 nm with polarized excitation and emission. The studied emitters showed continuous blinking; however, bleaching can be suppressed using a polymethyl methacrylate coating. Furthermore, hydrogen termination increased the density of single photon emitters. Our results will contribute to the identification of quantum systems in ZnO. &copy; 2014 AIP Publishing LLC.
Lem, L.L.C., Phillips, M.R. & Ton-That, C. 2014, 'Controlling the visible luminescence in hydrothermal ZnO', Journal of Luminescence, vol. 154, pp. 387-391.
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Cathodoluminescence spectra have been measured in hydrothermal and hydrogen-doped ZnO at different excitation densities and temperatures to investigate the emission efficiencies of near-band-edge (NBE), green and yellow luminescence bands. The NBE intensity depends linearly on the electron beam excitation as expected for excitonic recombination character. The intensities of the green and yellow bands are highly dependent not only on the excitation density but also on temperature. At high excitation densities ZnO exhibits dominant green emission at room temperature; the intensity of the green band can be further controlled by doping ZnO with hydrogen, which passivates green luminescence centers. Conversely at small excitation densities (< 0.1 nA) and low temperatures the visible luminescence from ZnO is predominantly yellow due to the abundance of Li in hydrothermal ZnO. The results are explained by differences in the recombination kinetics and the relative concentrations of the green and yellow centers, and illustrate that single-color emission can be achieved in ZnO by adjusting the excitation power and temperature. &copy; 2014 Published by Elsevier B.V. All rights reserved.
Chan, K.S., Ton-That, C., Vines, L., Choi, S., Phillips, M.R., Svensson, B.G., Jagadish, C. & Wong-Leung, J. 2014, 'Effects of high temperature annealing on defects and luminescence properties in H implanted ZnO', Journal of Physics D: Applied Physics, vol. 47, no. 34.
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The evolution of luminescence properties and voids formation with respect to annealing temperature in H implanted ZnO was investigated by depth-resolved cathodoluminescence spectroscopy (DRCLS), transmission electron microscopy and secondary ion mass spectrometry (SIMS). The annealing temperature is found to induce noticeable changes to the shape, size and empty volume density of the cavities. DRCLS results also reveal that the green emission is influenced by different annealing temperatures. In particular, the 600 &deg;C anneal produces a strong quenching of the green emission in the implanted region, while after the 800 &deg;C anneal a significant enhancement near the surface is observed. The annealing at 600 &deg;C also results in an uncommon violet emission at ?3.1 eV that is not observed after a higher annealing temperature. A clear correlation between the violet emission, vacancies and Li is revealed from comparison between the DRCLS intensities and SIMS data. &copy; 2014 IOP Publishing Ltd.
Ton-That, C., Lem, L.L.C., Phillips, M.R., Reisdorffer, F., Mevellec, J., Nguyen, T.-.P., Nenstiel, C. & Hoffmann, A. 2014, 'Shallow carrier traps in hydrothermal ZnO crystals', New Journal of Physics, vol. 16.
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Native and hydrogen-plasma induced shallow traps in hydrothermally grown ZnO crystals have been investigated by charge-based deep level transient spectroscopy, photoluminescence and cathodoluminescence microanalysis. The as-grown ZnO exhibits a trap state at 23 meV, while H-doped ZnO produced by plasma doping shows two levels at 22 meV and 11 meV below the conduction band. As-grown ZnO displays the expected thermal decay of bound excitons with increasing temperature from 7 K, while we observed an anomalous behaviour of the excitonic emission in H-doped ZnO, in which its intensity increases with increasing temperature in the range 140-300 K. Based on a multitude of optical results, a qualitative model is developed which explains the Y line structural defects, which act as an electron trap with an activation energy of 11 meV, being responsible for the anomalous temperature-dependent cathodoluminescence of H-doped ZnO. &copy; 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
Callsen, G., Wagner, M.R., Reparaz, J.S., Nippert, F., Kure, T., Kalinowski, S., Hoffmann, A., Ford, M.J., Phillips, M.R., Dalmau, R.F., Schlesser, R., Collazo, R. & Sitar, Z. 2014, 'Phonon pressure coefficients and deformation potentials of wurtzite AlN determined by uniaxial pressure-dependent Raman measurements', Physical Review B - Condensed Matter and Materials Physics, vol. 90, no. 20.
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We studied bulk crystals of wurtzite AlN by means of uniaxial pressure-dependent Raman measurements. As a result, we derive the phonon pressure coefficients and deformation potentials for all zone center optical phonon modes. For the A1 and E1 modes, we further experimentally determined the uniaxial pressure dependence of their longitudinal optical-transverse optical (LO-TO) splittings. Our experimental approach delivers new insight into the large variance among previously reported phonon deformation potentials, which are predominantly based on heteroepitaxial growth of AlN and the ball-on-ring technique. Additionally, the measured phonon pressure coefficients are compared to their theoretical counterparts obtained by density functional theory implemented in the siesta package. Generally, we observe a good agreement between the calculated and measured phonon pressure coefficients but some particular Raman modes exhibit significant discrepancies similar to the case of wurtzite GaN and ZnO, clearly motivating the presented uniaxial pressure-dependent Raman measurements on bulk AlN crystals.
Anantachaisilp, S., Anantachaisilp, S., Smith, S.M., Ton-That, C., Osotchan, T., Moon, A.R. & Phillips, M.R. 2014, 'Tailoring deep level surface defects in ZnO nanorods for high sensitivity ammonia gas sensing', Journal of Physical Chemistry C, vol. 118, no. 46, pp. 27150-27156.
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&copy; 2014 American Chemical Society. The influence of deep level surface defects on electrical and gas sensing properties of ZnO nanorods NH3(g) sensors was studied. ZnO nanorods 50-60 nm in diameter were synthesized via low-temperature hydrothermal growth at 90&deg;C on sapphire substrates. The as-grown nanorods exhibited a cathodoluminescence (CL) peak centered at 1.90 eV (YL), attributed to LiZn deep acceptors or O interstitials. Subsequent annealing in O2 at 1 atm and Zn vapor at 650&deg;C produced broad CL peaks centered at 1.70 eV (RL) and 2.44 eV (GL), respectively. The RL and GL have been ascribed to acceptor-like VZn and donor-like VO related centers, respectively. Electrical and gas sensing measurements established that the NH3 gas response sensitivity was 22.6 for O2 anneal (RL), 1.4 for Zn vapor anneal (GL), and 4.1 for the as-grown (YL) samples. Additionally, treatment in H-plasma quenched the RL and inverted the NH3 electrical response due to the incorporation of H donors. Changes in the gas sensing response are explained by a shift in the position of the ZnO Fermi level relative to the chemical potential of NH3 gas due to the creation of near surface donor or acceptors. These data confirm that ZnO nanorods arrays can be tailored to detect specific gas species. (Chemical Equation Presented).
Davis, J., Short, K., Wuhrer, R., Phillips, M.R., Lumpkin, G.R. & Whittle, K.R. 2013, 'Electron backscatter diffraction characterization of plasma immersion ion implantation effects in stainless steel', Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, vol. 295, pp. 38-41.
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In these experiments plasma immersion ion implantation is utilised to simulate some of the radiation effects in a nuclear reactor environment. Scanning electron microscopy using the angular selective backscatter detector has revealed observable changes in crystallographic contrast after irradiation with helium ions. Further studies using electron backscatter diffraction in both plan and cross section view allow us to visualize the extent and depth of damage and observe differences in the behavior of different crystalline phases present in several grades of stainless steel. &copy; 2012 Elsevier B.V. All rights reserved.
Zhu, L., Ton-That, C. & Phillips, M.R. 2013, 'Nitrogen incorporation in ZnO nanowires using N2O dopant gas', Materials Letters, vol. 99, pp. 42-45.
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Aligned nitrogen-doped ZnO nanowires were grown by chemical vapour deposition using Au catalyst. N incorporation was achieved through the introduction of N2O gas as a dopant source and confirmed by Raman spectroscopy, which reveals additional N-related modes at 275, 580 and 642 cm-1. The nanowires have a hexagonal faceted shape and are predominantly grown along the [001] direction. The nanowire morphology is unaffected by N incorporation. The luminescence peak at 3.24 eV was monitored as a function of N2O content. Intensity analysis of this band reveals that it can be partly attributed to donor-acceptor pair (DAP) emission originating from the N doping. &copy; 2013 Elsevier B.V. All rights reserved.
Khachadorian, S., Papagelis, K., Ogata, K., Hofmann, S., Phillips, M.R. & Thomsen, C. 2013, 'Elastic Properties of Crystalline-Amorphous Core-Shell Silicon Nanowires', JOURNAL OF PHYSICAL CHEMISTRY C, vol. 117, no. 8, pp. 4219-4226.
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Martin, A.A., Phillips, M.R. & Toth, M. 2013, 'Dynamic surface site activation: A rate limiting process in electron beam induced etching', ACS Applied Materials and Interfaces, vol. 5, no. 16, pp. 8002-8007.
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We report a new mechanism that limits the rate of electron beam induced etching (EBIE). Typically, the etch rate is assumed to scale directly with the precursor adsorbate dissociation rate. Here, we show that this is a special case, and that the rate can instead be limited by the concentration of active sites at the surface. Novel etch kinetics are expected if surface sites are activated during EBIE, and observed experimentally using the electron sensitive material ultra nanocrystalline diamond (UNCD). In practice, etch kinetics are of interest because they affect resolution, throughput, proximity effects, and the topography of nanostructures and nanostructured devices fabricated by EBIE. &copy; 2013 American Chemical Society.
Wagner, M.R., Wagner, M.R., Callsen, G., Reparaz, J.S., Reparaz, J.S., Kirste, R., Kirste, R., Hoffmann, A., Rodina, A.V., Schleife, A., Schleife, A., Schleife, A., Bechstedt, F., Bechstedt, F. & Phillips, M.R. 2013, 'Effects of strain on the valence band structure and exciton-polariton energies in ZnO', Physical Review B - Condensed Matter and Materials Physics, vol. 88, no. 23.
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The uniaxial stress dependence of the band structure and the exciton-polariton transitions in wurtzite ZnO is thoroughly studied using modern first-principles calculations based on the HSE+G0W0 approach, kp modeling using the deformation potential framework, and polarized photoluminescence measurements. The ordering of the valence bands [A(?7), B(?9), C(?7)] is found to be robust even for high uniaxial and biaxial strains. Theoretical results for the uniaxial pressure coefficients and splitting rates of the A, B, and C valence bands and their optical transitions are obtained including the effects of the spin-orbit interaction. The excitonic deformation potentials are derived and the stress rates for hydrostatic pressure are determined based on the results for uniaxial and biaxial stress. In addition, the theory for the stress dependence of the exchange interaction and longitudinal-transversal splitting of the exciton polaritons is developed using the basic exciton functions of the quasicubic approximation and taking the interaction between all exciton states into account. It is shown that the consideration of these effects is crucial for an accurate description of the stress dependence of the optical spectra in ZnO. The theoretical results are compared to polarized photoluminescence measurements of different ZnO substrates as function of uniaxial pressure and experimental values reported in the literature demonstrating an excellent agreement with the computed pressure coefficients. &copy; 2013 American Physical Society.
Choi, S., Ton-That, C., Phillips, M.R. & Aharonovich, I. 2013, 'Observation of whispering gallery modes from hexagonal ZnO microdisks using cathodoluminescence spectroscopy', Applied Physics Letters, vol. 103, no. 17.
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Zinc oxide hexagonal microdisks with diameters ranging from 3 ?m up to 15 ?m were fabricated by thermal chemical vapour deposition. Optical characterisation of ZnO microdisks was performed using low temperature (80 K) cathodoluminescence (CL) imaging and spectroscopy. The microdisks exhibited green luminescence locally distributed near the hexagonal boundary of the ZnO microdisks. High resolution CL spectra of the ZnO microdisks revealed whispering gallery modes (WGMs) emission. The experimentally observed WGMs were in excellent agreement with the predicted theoretical positions calculated using a plane wave model. This work could provide the means for ZnO microdisk devices operating in the green spectral range. &copy; 2013 AIP Publishing LLC.
Gogova, D., Petrov, P.P., Buegler, M., Wagner, M.R., Nenstiel, C., Callsen, G., Schmidbauer, M., Kucharski, R., Zajac, M., Dwilinski, R., Phillips, M.R., Hoffmann, A. & Fornari, R. 2013, 'Structural and optical investigation of non-polar (1-100) GaN grown by the ammonothermal method', Journal of Applied Physics, vol. 113, no. 20, pp. 203513-203513.
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He, R., Tang, B., Ton-That, C., Phillips, M. & Tsuzuki, T. 2013, 'Physical structure and optical properties of Co-doped ZnO nanoparticles prepared by co-precipitation', Journal of Nanoparticle Research, vol. 15, no. 11.
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The structural and optical properties of cobalt-doped zinc oxide (Co-doped ZnO) nanoparticles have been investigated. The nanopowder with Co concentrations up to 5 at% was synthesized by a coprecipitation method. The physical structure and the chemical states of the Co-doped ZnO were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-Visible reflectance and cathodoluminescence (CL) spectroscopy. The results show that cobalt ions predominantly occupy Zn2+ sites in the wurtzite crystal lattice and possess a valence state of 2+. CL analysis revealed that the incorporation of Co2+ creates a new emission band at 1.85 eV, but quenched the near-band-edge luminescence. &copy; Springer Science+Business Media 2013.
Ton-That, C., Foley, M., Phillips, M.R., Tsuzuki, T. & Smith, Z. 2012, 'Correlation between the structural and optical properties of Mn-doped ZnO nanoparticles', Journal of Alloys and Compounds, vol. 522, pp. 114-117.
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The crystallographic and optical properties of Mn-doped ZnO nanoparticles prepared by a sol-gel process have been investigated by X-ray diffraction, UV-visible absorption spectroscopy and cathodoluminescence microanalysis. X-ray diffraction reveals that the nanoparticles have hexagonal wurtzite crystal structure, with the lattice constants along the a- and c-axes increasing with increasing Mn concentration from 0 to 2.4 at%. For all Mn concentrations in this range, the nanoparticles are essentially free of native point defects so that they exhibit only band-edge luminescence. The optical bandgap and band-edge emission energies for Mn-doped ZnO were found to increase in proportion to the lattice constants. The direct correlation between the bandgap and crystal structure suggests that the band-edge optical properties of Mn-doped ZnO is predominantly influenced by the amount of Mn atoms substituting Zn on the lattice sites. &copy; 2012 Elsevier B.V. All rights reserved.
Weston, L., Ton-That, C. & Phillips, M.R. 2012, 'Doping properties of hydrogen in ZnO', Journal of Materials Research, vol. 27, no. 17, pp. 2220-2224.
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The doping properties and stability of hydrogen in zinc oxide (ZnO) crystals have been investigated by cathodoluminescence (CL) spectroscopy. Hydrogen incorporation was achieved by hydrogen plasma at 200 &deg;C. The ZnO near-band-edge (NBE) peak is dramatically enhanced, while the green emission at 2.4 eV is quenched with increasing hydrogen incorporation. These effects are attributed to hydrogen passivating green luminescence centers, which are most likely negatively charged zinc vacancy defects. E-beam irradiation of H-doped ZnO crystals by an intense electron beam with ?W power reverses the hydrogen doping process. This effect is ascribed to the dissociation of H-related defects, formation of Chidden H2, and electromigration of H + under the influence of the local trapped charge-induced electric field. These results highlight the potential to modify the local luminescent properties of ZnO by e-beam irradiation. &copy; 2012 Materials Research Society.
Ton-That, C., Weston, L. & Phillips, M.R. 2012, 'Characteristics of point defects in the green luminescence from Zn- and O-rich ZnO', Physical Review B - Condensed Matter and Materials Physics, vol. 86, no. 11.
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Cathodoluminescence spectra have been measured to determine the characteristics of ubiquitous green luminescence (GL) in nonstoichiometric zinc oxide (ZnO). Zn- and O-rich ZnO were found to exhibit characteristic emissions at 2.53 eV [full width at half-maximum (FWHM) 340 meV] and 2.30 eV (FWHM 450 meV), respectively. Hydrogen was used to probe the physical nature of GL centers. The Zn-rich GL is enhanced upon H incorporation, whereas the O-rich GL is completely quenched as its underlying acceptor-like V Zn centers are passivated by H. The GL emission bands each exhibit remarkably different excitation-power dependencies. The Zn-rich GL follows a close to linear relationship with excitation power, while the O-rich GL exhibits a square-root dependence. Calculations based on bimolecular recombination equations show the defect concentration in Zn-rich ZnO is three orders of magnitude greater than that in O-rich ZnO, indicating V O is more readily formed than V Zn in thermochemical treatments of ZnO. &copy; 2012 American Physical Society.
Bishop, J., Toth, M., Phillips, M. & Lobo, C. 2012, 'Effects of oxygen on electron beam induced deposition of SiO2 using physisorbed and chemisorbed tetraethoxysilane', Applied Physics Letters, vol. 101, no. 21.
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Electron beam induced deposition (EBID) is limited by low throughput and purity of as-grown material. Co-injection of O2 with the growth precursor is known to increase both the purity and deposition rate of materials such as SiO2 at room temperature. Here, we show that O2 inhibits rather than enhances EBID from tetraethoxysilane (TEOS) precursor at elevated temperatures. This behavior is attributed to surface site competition between chemisorbates at elevated temperature, and TEOS decomposition by atomic oxygen produced through electron dissociation of physisorbed O2 at room temperature. &copy; 2012 American Institute of Physics.
Bishop, J., Lobo, C.J., Martin, A., Ford, M., Phillips, M. & Toth, M. 2012, 'Role of activated chemisorption in gas-mediated electron beam induced deposition', Physical Review Letters, vol. 109, no. 14.
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Models of adsorbate dissociation by energetic electrons are generalized to account for activated sticking and chemisorption, and used to simulate the rate kinetics of electron beam induced chemical vapor deposition (EBID). The model predicts a novel temperature dependence caused by thermal transitions from physisorbed to chemisorbed states that govern adsorbate coverage and EBID rates at elevated temperatures. We verify these results by experiments that also show how EBID can be used to deposit high purity materials and characterize the rates and energy barriers that govern adsorption. &copy; 2012 American Physical Society.
Lobo, C.J., Martin, A., Phillips, M.R. & Toth, M. 2012, 'Electron beam induced chemical dry etching and imaging in gaseous NH 3 environments', Nanotechnology, vol. 23, no. 37.
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We report the use of ammonia (NH 3) vapor as a new precursor for nanoscale electron beam induced etching (EBIE) of carbon, and an efficient imaging medium for environmental scanning electron microscopy (ESEM). Etching is demonstrated using amorphous carbonaceous nanowires grown by electron beam induced deposition (EBID). It is ascribed to carbon volatilization by hydrogen radicals generated by electron dissociation of NH 3 adsorbates. The volatilization process is also effective at preventing the buildup of residual hydrocarbon impurities that often compromise EBIE, EBID and electron imaging. We also show that ammonia is a more efficient electron imaging medium than H 2O, which up to now has been the most commonly used ESEM imaging gas. &copy; 2012 IOP Publishing Ltd.
Demers, H., Poirier-Demers, N., Phillips, M.R., de Jonge, N. & Drouin, D. 2012, 'Three-Dimensional Electron Energy Deposition Modeling of Cathodoluminescence Emission near Threading Dislocations in GaN and Electron-Beam Lithography Exposure Parameters for a PMMA Resist', MICROSCOPY AND MICROANALYSIS, vol. 18, no. 6, pp. 1220-1228.
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Roczen, M., Schade, M., Malguth, E., Callsen, G., Barthel, T., Gref, O., Töfflinger, J.A., Schöpke, A., Schmidt, M., Leipner, H.S., Ruske, F., Phillips, M.R., Hoffmann, A., Korte, L. & Rech, B. 2012, 'Structural investigations of silicon nanostructures grown by self-organized island formation for photovoltaic applications', Applied Physics A: Materials Science and Processing, vol. 108, no. 3, pp. 719-726.
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The self-organized growth of crystalline silicon nanodots and their structural characteristics are investigated. For the nanodot synthesis, thin amorphous silicon (a-Si) layers with different thicknesses have been deposited onto the ultrathin (2 nm) oxidized (111) surface of Si wafers by electron beam evaporation under ultrahigh vacuum conditions. The solid phase crystallization of the initial layer is induced by a subsequent in situ annealing step at 700&deg;C, which leads to the dewetting of the initial a-Si layer. This process results in the self-organized formation of highly crystalline Si nanodot islands. Scanning electron microscopy confirms that size, shape, and planar distribution of the nanodots depend on the thickness of the initial a-Si layer. Cross-sectional investigations reveal a single-crystalline structure of the nanodots. This characteristic is observed as long as the thickness of the initial a-Si layer remains under a certain threshold triggering coalescence. The underlying ultra-thin oxide is not structurally affected by the dewetting process. Furthermore, a method for the fabrication of close-packed stacks of nanodots is presented, in which each nanodot is covered by a 2 nm thick SiO 2 shell. The chemical composition of these ensembles exhibits an abrupt Si/SiO 2 interface with a low amount of suboxides. A minority charge carrier lifetime of 18 ?s inside of the nanodots is determined. &copy; 2012 Springer-Verlag.
Callsen, G., Callsen, G., Reparaz, J.S., Wagner, M.R., Kirste, R., Nenstiel, C., Nenstiel, C., Hoffmann, A. & Phillips, M.R. 2011, 'Phonon deformation potentials in wurtzite GaN and ZnO determined by uniaxial pressure dependent Raman measurements', Applied Physics Letters, vol. 98, no. 6.
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We report the phonon deformation potentials of wurtzite GaN and ZnO for all zone center optical phonon modes determined by Raman measurements as a function of uniaxial pressure. Despite all the structural and optical similarities between these two material systems, the pressure dependency of their vibrational spectra exhibits fundamental distinctions, which is attributed to their different bond ionicities. In addition, the LO-TO splitting of the A1 and E1 phonon modes is analyzed which yields insight into the uniaxial pressure dependency of Born's transverse effective charge e T*. &copy; 2011 American Institute of Physics.
Wagner, M.R., Callsen, G., Reparaz, J.S., Schulze, J.H., Kirste, R., Cobet, M., Ostapenko, I.A., Rodt, S., Nenstiel, C., Kaiser, M., Hoffmann, A., Rodina, A.V., Phillips, M.R., Lautenschläger, S., Eisermann, S. & Meyer, B.K. 2011, 'Bound excitons in ZnO: Structural defect complexes versus shallow impurity centers', Physical Review B - Condensed Matter and Materials Physics, vol. 84, no. 3.
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ZnO single crystals, epilayers, and nanostructures often exhibit a variety of narrow emission lines in the spectral range between 3.33 and 3.35 eV which are commonly attributed to deeply bound excitons (Y lines). In this work, we present a comprehensive study of the properties of the deeply bound excitons with particular focus on the Y0 transition at 3.333 eV. The electronic and optical properties of these centers are compared to those of the shallow impurity related exciton binding centers (I lines). In contrast to the shallow donors in ZnO, the deeply bound exciton complexes exhibit a large discrepancy between the thermal activation energy and localization energy of the excitons and cannot be described by an effective mass approach. The different properties between the shallow and deeply bound excitons are also reflected by an exceptionally small coupling of the deep centers to the lattice phonons and a small splitting between their two electron satellite transitions. Based on a multitude of different experimental results including magnetophotoluminescence, magnetoabsorption, excitation spectroscopy (PLE), time resolved photoluminescence (TRPL), and uniaxial pressure measurements, a qualitative defect model is developed which explains all Y lines as radiative recombinations of excitons bound to extended structural defect complexes. These defect complexes introduce additional donor states in ZnO. Furthermore, the spatially localized character of the defect centers is visualized in contrast to the homogeneous distribution of shallow impurity centers by monochromatic cathodoluminescence imaging. A possible relation between the defect bound excitons and the green luminescence band in ZnO is discussed. The optical properties of the defect transitions are compared to similar luminescence lines related to defect and dislocation bound excitons in other II-VI and III-V semiconductors. &copy; 2011 American Physical Society.
Callsen, G., Reparaz, J.S., Wagner, M.R., Vierck, A., Phillips, M.R., Thomsen, C. & Hoffmann, A. 2011, 'Titanium-assisted growth of silica nanowires: From surface-matched to free-standing morphologies', Nanotechnology, vol. 22, no. 40.
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We report on an oxide-assisted growth technique for silica nanowires which allows tuning the growth from surface-matched nanowires to free-standing morphologies based on growth control by Ti in the role of a catalyst and surfactant. Using an adjustable Ti concentration, we grew silica nanowires with lengths ranging from 100nm up to several millimetres whose defect chemistry was analysed by electron microscopy tools, monochromatic cathodoluminescence imaging and time resolved photoluminescence spectroscopy. The knowledge of the luminescence properties and the related defect occurrence along with their spatial distribution is pivotal for advancing silica nanowire growth in order to realize successful device designs based on self-assembled Si/SiOx nanostructures. We demonstrate a core-shell structure of the grown nanowires with a highly luminescent 150nm thick shell and outstandingly fast decaying dynamics (?1ns) for glass-like materials. The conjunction of the observed efficient and stable luminescences with their attributed decaying behaviours suggests applications for silica nanowires such as active and passive optical interconnectors and white light phosphors. The identification of a time domain difference for the spectral regime from 2.3 to 3.3eV, within the confined spatial dimensions of a single nanowire, is very promising for future, e.g.data transmission applications, employing silica nanowires which exhibit achievable compatibility with commonly applied silicon-based electronics. A qualitative growth model based on silica particle diffusion and Ti-assisted seed formation is developed for the various types of segregated silica nanowires which extends commonly assumed oxide-assisted growth mechanisms. &copy; IOP Publishing Ltd.
Chen, P.P.-.T., Downes, J.E., Fernandes, A.J., Butcher, K.S.A., Wintrebert-Fouquet, M., Wuhrer, R. & Phillips, M.R. 2011, 'Effects of crystallinity and chemical variation on apparent band-gap shift in polycrystalline indium nitride', THIN SOLID FILMS, vol. 519, no. 6, pp. 1831-1836.
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Lem, L.L.C., Ton-That, C. & Phillips, M.R. 2011, 'Distribution of visible luminescence centers in hydrogen-doped ZnO', Journal of Materials Research, vol. 26, no. 23, pp. 2912-2915.
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ZnO crystals have been investigated by scanning cathodoluminescence microscopy and spectroscopy at 80 K following hydrogen incorporation by plasma exposure. The intensity of the ZnO near-band-edge (NBE) emission is greatly enhanced while the defect-related green emission is quenched following plasma treatment. These effects are attributed to the passivation of zinc vacancies by hydrogen. The green and yellow intensities and their intensity ratios to the NBE vary with excitation depth for both undoped and H-doped ZnO crystals. The intensities of the green and yellow emissions exhibit sublinear dependencies on electron beam excitation density while the NBE intensity increases linearly with the excitation density. These saturation effects with increasing excitation density must be taken into account when assessing defects in ZnO by luminescence characterization. &copy; Copyright Materials Research Society 2011.
Sprouster, D.J., Ruffell, S., Bradby, J.E., Williams, J.S., Lockrey, M.N., Phillips, M.R., Major, R.C. & Warren, O.L. 2011, 'Structural characterization of B-doped diamond nanoindentation tips', Journal of Materials Research, vol. 26, no. 24, pp. 3051-3057.
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Copyright &copy; Materials Research Society 2011. We report on the electrical and structural properties of boron-doped diamond tips commonly used for in-situ electromechanical testing during nanoindentation. The boron dopant environment, as evidenced by cathodoluminescence (CL) microscopy, revealed significantly different boron states within each tip. Characteristic emission bands of both electrically activated and nonelectrically activated boron centers were identified in all boron-doped tips. Surface CL mapping also revealed vastly different surface properties, confirming a high amount of nonelectrically activated boron clusters at the tip surface. Raman microspectroscopy analysis showed that structural characteristics at the atomic scale for boron-doped tips also differ significantly when compared to an undoped diamond tip. Furthermore, the active boron concentration, as inferred via the Raman analysis, varied greatly from tip-to-tip. It was found that tips (or tip areas) with low overall boron concentration have a higher number of electrically inactive boron, and thus non-Ohmic contacts were made when these tips contacted metallic substrates. Conversely, tips that have higher boron concentrations and a higher number of electrically active boron centers display Ohmic-like contacts. Our results demonstrate the necessity to understand and fully characterize the boron environments, boron concentrations, and atomic structure of the tips prior to performing in situ electromechanical experiments, particularly if quantitative electrical data are required.
Lockrey, M.N. & Phillips, M. 2011, 'Characterisation Of The Optical Properties Of InGaN MQW Structures Using A Combined Sem And Cl Spectral Mapping System', Journal of Semiconductors, vol. 32, no. 1, pp. 0-0.
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We demonstrate the ability of a combined scanning electron microscope and cathodoluminescence (CL) spectral mapping system to provide important spatially resolved information. The degree of inhomogeneity in spectral output across a multi-quantum well sample is measured using the SEM-CL system as well as measuring the efficiency roll-off with increasing carrier concentration. The effects of low energy electron beam modification on the InGaN/GaN multi quantum wells have also been characterized.
Foley, M., Ton-That, C. & Phillips, M.R. 2010, 'Luminescent properties of ZnO structures grown with a vapour transport method', Thin Solid Films, vol. 518, no. 15, pp. 4231-4233.
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ZnO structures were synthesised on the sapphire (112?0) substrate by a vapour transport method in a gas flowing furnace. The influence of the oxygen content in the gas mixture on the morphology and luminescent properties of ZnO structures grown on a strip-like substrate was investigated, with all other growth parameters being kept nominally identical. Integrated electron microscopy and cathodoluminescence analysis shows gradual variations of structural and optical emission properties for ZnO structures grown on the long substrate. Defect-related green luminescence of ZnO is found to be highly dependent on the oxygen vapour in the growth region of the furnace. Our findings demonstrate that the green luminescence is associated with oxygen deficiency in ZnO. &copy; 2009 Elsevier B.V. All rights reserved.
White, R., Thomas, P., Phillips, M.R., Moran, K. & Wuhrer, R. 2010, 'X-ray mapping and scatter diagram analysis of the discoloring products resulting from the interaction of artist's pigments', Microscopy and Microanalysis, vol. 16, no. 5, pp. 594-598.
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The discoloring interaction between the artist's pigments cadmium yellow and the copper-containing malachite, an interaction that is conjectured to cause black spotting in oil paintings of the 19th and early 20th centuries, was examined using X-ray mapping and scatter diagram analysis. The application of these coupled techniques confirmed that copper sulfide phases were produced during discoloration reaction. Scatter diagram analysis indicated that two copper sulfide stoichiometries (CuS and Cu3S2) were present as reaction products where previously only crystalline CuS (covellite) had been identified by X-ray diffraction. The results demonstrate the potential of X-ray mapping coupled with scatter diagram analysis for the identification of both crystalline and X-ray amorphous phases produced by such complex heterogeneous interactions and their applicability to the investigation of interactions of artists' pigments. &copy; Microscopy Society of America 2010.
Coutts, M.J., Zareie, H.M., Cortie, M.B., Phillips, M.R., Wuhrer, R. & McDonagh, A.M. 2010, 'Exploiting zinc oxide re-emission to fabricate periodic arrays', ACS Applied Materials and Interfaces, vol. 2, no. 6, pp. 1774-1779.
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The synthesis of hexagonal ring-shaped structures of zinc oxide using nanosphere lithography and metal/metal oxide sputtering is demonstrated. This synthesis exploits the surface re-emission of zinc oxide to deposit material in regions lying out of the line-of-sight of the sputtering source. These rings can nucleate the hydrothermal growth of zinc oxide crystals. Control over the growth could be exercised by varying growth solution concentration or temperature or by applying an external potential. &copy; 2010 American Chemical Society.
Ton-That, C., Foley, M., Lem, L.L.C., McCredie, G., Phillips, M.R. & Cowie, B.C.C. 2010, 'Diffusion synthesis and electronic properties of Fe-doped ZnO', Materials Letters, vol. 64, no. 3, pp. 386-388.
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Fe-doped ZnO was successfully fabricated by thermal in-diffusion of Fe into ZnO crystals. X-ray absorption near edge structure (XANES), photoemission and cathodoluminescence (CL) spectroscopy have been combined to examine the Fe diffusion and its effects on the electronic and optical properties of the crystal. Depth-resolved CL demonstrates that Fe in-diffusion occurs to at least 4 ?m depth and results in intense green luminescence, whereas the undoped crystal exhibits only the ZnO near-band-edge emission. XANES and valence-band photoemission show that Fe is incorporated as Fe2+/3+ ions on substitutional Zn sites. The results suggest that the variation in the CL properties is due to a change in the oxygen vacancy charge state as a result of electron transfer from Fe. Crown Copyright &copy; 2009.
Phillips, M.R., Drouin, D., Moody, S.J. & Ton-That, C. 2009, 'Imaging fundamental electronic excitations at high spatial resolution using scanning cathodoluminescence microscopy', Microscopy and Microanalysis, vol. 15, no. SUPPL. 2, pp. 670-671.
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Godlewski, M., Wojcik-Glodowska, A., Guziewicz, E., Yatsunenko, S., Zakrzewski, A., Dumont, Y., Chikoidze, E. & Phillips, M.R. 2009, 'Optical properties of manganese doped wide band gap ZnS and ZnO', OPTICAL MATERIALS, vol. 31, no. 12, pp. 1768-1771.
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Moody, S.J., Phillips, M.R. & Toth, M. 2009, 'Assessment of sem image quality using 1d power spectral density estimation', Microscopy and Microanalysis, vol. 15, no. SUPPL. 2, pp. 48-49.
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Bertinshaw, J., Kirkup, L., Phillips, M. & Placido, F. 2008, 'A system for supplying constant electrical power for postprocessing tin-doped indium oxide films', Review of Scientific Instruments, vol. 79, no. 7.
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Annealing tin doped indium oxide (ITO) thin films by self-heating shows potential for reducing the crystallization temperature required to optimize the optical and electrical properties of the films. It also shows promise as a cost effective method of studying the heat treatment process in situ. A computer based solution was developed to allow for a precise control over the annealing process. To anneal at a fixed temperature, a feedback loop senses changes in the resistance of the sample and adjusts the current across the load accordingly to ensure constant delivery of power to an ITO film. &copy; 2008 American Institute of Physics.
Malguth, E., Hoffmann, A. & Phillips, M.R. 2008, 'Fe in III-V and II-VI semiconductors', PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, vol. 245, no. 3, pp. 455-480.
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Ton-That, C., Phillips, M.R., Foley, M., Moody, S.J. & Stampfl, A.P.J. 2008, 'Surface electronic properties of ZnO nanoparticles', Applied Physics Letters, vol. 92, no. 26.
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The surface electronic structure of ZnO nanoparticles has been studied with photoemission and x-ray absorption spectroscopies. Contrary to expectation, ZnO:Zn phosphor nanoparticles were found to contain a lower oxygen vacancy density on the surface than undoped ZnO counterparts, but oxygen vacancies are in different chemical environments. Cathodoluminescence shows intense green luminescence from the ZnO:Zn surface, while the undoped nanoparticles exhibit only the near-band-edge emission. The results indicate the roles of surface oxygen vacancies and their environment in the previously unexplained green luminescence from the ZnO:Zn material. &copy; 2008 American Institute of Physics.
Foley, M., Ton-That, C. & Phillips, M.R. 2008, 'Cathodoluminescence inhomogeneity in ZnO nanorods', Applied Physics Letters, vol. 93, no. 24.
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Luminescence properties of vertically aligned, crystalline ZnO nanorods are studied by cathodoluminescence (CL) spectroscopy and microscopy. Results show that luminescence characteristics vary dramatically with location on the nanorod as well as CL excitation depth. CL inhomogeneity is observed between the nanorod tip and sidewalls, accompanied by a variation in the chemical environment of surface oxygen ions as probed by photoemission spectroscopy. Our findings demonstrate that CL can provide useful information on the local optical properties of nanostructured materials, which is simply beyond the capability of other methods. &copy; 2008 American Institute of Physics.
Morgan, S.W. & Phillips, M.R. 2008, 'High bandwidth secondary electron detection in variable pressure scanning electron microscopy using a Frisch grid', Journal of Physics D: Applied Physics, vol. 41, no. 5.
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The bandwidth and contrast of secondary electron (SE) images obtained using variable pressure scanning electron microscopy are enhanced when a grounded Frisch grid is placed between the SE detecting anode and the negatively biased stage. The improvement in SE image quality occurs as a consequence of the grounded Frisch grid electrostatically screening the 'slow' induced ion current signal, generated below the grid, from the induced current detected above the grid by the anode. Ion induced artefacts, such as image smearing at fast scan rates, are virtually eliminated using a Frisch grid. Gas amplification data are presented to illustrate that gas gain can be optimized by varying the Frisch grid-stage (amplification region) separation Frisch grid-anode (drift region) separation and stage bias. &copy; 2008 IOP Publishing Ltd.
Mokkapati, S., Wong-Leung, J., Tan, H.H., Jagadish, C., McBean, K.E. & Phillips, M.R. 2008, 'Tuning the bandgap of InAs quantum dots by selective-area MOCVD', JOURNAL OF PHYSICS D-APPLIED PHYSICS, vol. 41, no. 8.
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Zareie, H.M., Morgan, S.W., Moghaddam, M., Maaroof, A.I., Cortie, M.B. & Phillips, M.R. 2008, 'Nanocapacitive circuit elements', ACS Nano, vol. 2, no. 8, pp. 1615-1619.
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"Natural" lithography was used to prepare arrays of nanoscale capacitors on silicon. The capacitance was verified by a novel technique based on the interaction of a charged substrate with the electron beam of a scanning electron microscope. The "nanocapacitors" possessed a capacitance of ?1 10-16F and were observed to hold charge for over an hour. Our results indicate that fabricating nanostructures using natural lithography may provide a viable alternative for future nanoelectronic devices. &copy; 2008 American Chemical Society.
Wuhrer, R., Moran, K. & Phillips, M. 2008, 'Multi-Detector X-Ray Mapping and Generation of Correction Factor Images for Problem Solving', Microscopy & Microanalysis, vol. 14, no. S2, pp. 1108-1109.
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X-ray mapping with Silicon Drift detectors (SDDs) and multi-EDS detector systems has become an invaluable analysis technique because the time to perform an x-ray map is reduced considerably. Live x-ray imaging can now been performed with so much data collected in a matter of minutes. The use of multi-EDS detector systems has made this form of mapping even quicker and has also given users the ability to map minor and trace elements very accurately. How the data is collected and summed with multi-EDS detectors is very critical for accurate quantitative x-ray mapping (QXRM).
Yang, J., Li, S., Li, Z.W., McBean, K. & Phillips, M.R. 2008, 'Origin of excitonic emission suppression in an individual ZnO nanobelt', Journal of Physical Chemistry C, vol. 112, no. 27, pp. 10095-10099.
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The near band edge emissions of an individual ZnO nanobelt were investigated by cathodoluminescence spectroscopy, which has unique advantages in higher spatial resolution, orientation, and environmental independence over the conventional photoluminescence spectroscopy. The results show that the presence of a large surface-to-volume ratio is the determinant to suppress the formation of excitons in ZnO nanobelts. Ab initio calculations show that a drastic decrease of density-of-state in the conduction band and increase in the valence band upon size reduction are the key consequence of the large surface-to-volume ratio, revealing the possible fundamental physical origin of exciton suppression. The weak exciton polarity also reduces the likelihood for an exciton to couple with longitudinal phonons. This causes a reduction in the first longitudinal phonon replica intensity and then a complete suppression of the second replica. Understanding the effect of large surface ratio upon the physical properties of ZnO nanomaterials may provide new insights into the fundamental science of nanotechnology for the development of optoelectronics. &copy; 2008 American Chemical Society.
Ton-That, C., Stockton, G., Phillips, M.R., Nguyen, T.-.P., Huang, C.H. & Cojocaru, A. 2008, 'Luminescence properties of poly- (phenylene vinylene) derivatives', Polymer International, vol. 57, no. 3, pp. 496-501.
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Background: Conjugated polymers, especially those of the poly(phenylene vinylene) (PPV) family, are promising candidates as emission material in light-emitting devices. The aim of this work was to investigate the dependence of the luminescence properties of PPV-based derivatives on their polymer structure, especially side groups. Results: Three PPV derivatives, BEHPPV, MEHPPV and MEHSPPV, were synthesised and characterised by photoluminescence (PL) and cathodoluminescence (CL) spectroscopies in the temperature range 10-300K. PL and CL spectra of the polymers exhibit similar luminescence peaks, which undergo a blue shift with increasing temperature. The shift in wavelength is accompanied by variations in the relative intensities of emission peaks. Both BEHPPV and MEHPPV display emission characteristics of the PPV backbone, but the peak of MEHPPV shifts to a longer wavelength in comparison with the corresponding peak of BEHPPV at the same temperature. The luminescence spectra of MEHSPPV, which has a sulfanyl incorporated in the side chain, are considerably different from those of the two other derivatives. Conclusions: The results demonstrate that the luminescence properties depend strongly on the chain conformations of the conjugated backbone, which are affected by polymer side chains. &copy; 2007 Society of Chemical Industry.
Ton-That, C., Foley, M. & Phillips, M.R. 2008, 'Luminescent properties of ZnO nanowires and as-grown ensembles', Nanotechnology, vol. 19, no. 41.
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Vertically aligned ZnO nanowires were synthesized on a sapphire (1120) substrate by vapour deposition and their light-emitting properties were characterized using photoluminescence and cathodoluminescence spectroscopies. Besides the nanowires, there exists a mosaic ZnO film on the substrate surface. Comparison of the luminescent properties of the as-grown ensemble and the nanowires extracted from it shows that the mosaic film is the major source of the defect-related green emission while the nanowires possess highly crystalline quality with virtually no defects. Photoemission spectroscopy shows that the valence band states associated with O 2p from the as-grown sample are diminished compared with those from the extracted nanowires. These findings suggest that the green emission partly arises from oxygen vacancies located on the surface of the mosaic film. &copy; IOP Publishing Ltd.
Ton-That, C., Phillips, M.R. & Nguyen, T.-.P. 2008, 'Blue shift in the luminescence spectra of MEH-PPV films containing ZnO nanoparticles', Journal of Luminescence, vol. 128, no. 12, pp. 2031-2034.
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Luminescence properties of nanocomposites consisting of ZnO nanoparticles in a conjugated polymer, poly [2-methoxy-5-(2?-ethyl hexyloxy)-phenylene vinylene] (MEH-PPV), were investigated. Photoluminescence measurements reveal a blue shift in the emission spectrum of MEH-PPV upon incorporation of ZnO nanoparticles into the polymer film while the emission is increasingly quenched with increasing ZnO concentration. In contrast, the structure of the polymer and its conjugation length are not affected by the presence of ZnO nanoparticles (up to 16 wt% ZnO) as revealed by Raman spectroscopy. The blue shift and photoluminescence quenching are explained by the separation of photogenerated electron-hole pairs at the MEH-PPV/ZnO interface and the charging of the nanoparticles. Crown Copyright &copy; 2008.
Malguth, E., Malguth, E., Hoffmann, A. & Phillips, M.R. 2008, 'Structural and optical inhomogeneities of Fe doped GaN grown by hydride vapor phase epitaxy', Journal of Applied Physics, vol. 104, no. 12.
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We present the results of cathodoluminescence experiments on a set of Fe doped GaN samples with Fe concentrations of 5 1017, 1 1018, 1 1019, and 2 1020 cm -3. These specimens were grown by hydride vapor phase epitaxy with different concentrations of Fe. The introduction of Fe is found to promote the formation of structurally inhomogeneous regions of increased donor concentration. We detect a tendency of these regions to form hexagonal pits at the surface. The locally increased carrier concentration leads to enhanced emission from the band edge and the internal T4 1 (G) - A6 1 (S) transition of Fe3+. In these areas, the luminescence forms a finely structured highly symmetric pattern, which is attributed to defect migration along strain-field lines. Fe doping is found to quench the yellow defect luminescence band and to enhance the blue luminescence band due to the lowering of the Fermi level and the formation of point defects, respectively. &copy; 2008 American Institute of Physics.
Veal, T.D., Piper, L.F.J., Phillips, M.R., Zareie, M.H., Lu, H., Schaff, W.J. & McConville, C.F. 2007, 'Doping-dependence of subband energies in quantized electron accumulation at InN surfaces', PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, vol. 204, no. 2, pp. 536-542.
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Godlewski, M., Skrobot, M., Guziewicz, E. & Phillips, M.R. 2007, 'Color tuning of white light emission from thin films of ZnSe', JOURNAL OF LUMINESCENCE, vol. 125, no. 1-2, pp. 85-91.
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Toth, M., Lobo, C.J., Knowles, W.R., Phillips, M.R., Postek, M.T. & Vladár, A.E. 2007, 'Nanostructure fabrication by ultra-high-resolution environmental scanning electron microscopy', Nano Letters, vol. 7, no. 2, pp. 525-530.
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Electron beam induced deposition (EBID) is a maskless nanofabrication technique capable of surpassing the resolution limits of resist-based lithography. However, EBID fabrication of functional nanostructures is limited by beam spread in bulk substrates, substrate charging, and delocalized film growth around deposits. Here, we overcome these problems by using environmental scanning electron microscopy (ESEM) to perform EBID and etching while eliminating charging artifacts at the nanoscale. Nanostructure morphology is tailored by slimming of deposits by ESEM imaging in the presence of a gaseous etch precursor and by pre-etching small features into a deposit (using a stationary or a scanned electron beam) prior to a final imaging process. The utility of this process is demonstrated by slimming of nanowires deposited by EBID, by the fabrication of gaps (between 4 and 7 nm wide) in the wires, and by the removal of thin films surrounding such nanowires. ESEM imaging provides a direct view of the slimming process, yielding process resolution that is limited by ESEM image resolution (~1 nm) and surface roughening occurring during etching. &copy; 2007 American Chemical Society.
Toth, M., Knowles, W.R. & Phillips, M.R. 2007, 'Imaging deep trap distributions by low vacuum scanning electron microscopy', APPLIED PHYSICS LETTERS, vol. 90, no. 7.
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Motlan, Zhu, G., Drozdowicz-Tomsia, K., McBean, K., Phillips, M.R. & Goldys, E.M. 2007, 'Annealing of ZnS nanocrystals grown by colloidal synthesis', OPTICAL MATERIALS, vol. 29, no. 12, pp. 1579-1583.
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Godlewski, M., Yatsunenko, S., Ivanov, V.Y., Drozdowicz-Tomsia, K., Goldys, E.M., Phillips, M.R., Klar, P.J. & Heimbrodt, W. 2007, 'Mechanisms of enhancement of light emission in nanostructures of II-VI compounds doped with manganese', LOW TEMPERATURE PHYSICS, vol. 33, no. 2-3, pp. 192-196.
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Zhang, H.Z., Phillips, M.R., Fitz Gerald, J.D., Yu, J. & Chen, Y. 2006, 'Patterned growth and cathodoluminescence of conical boron nitride nanorods', Applied Physics Letters, vol. 88, no. 9.
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We demonstrate a simple and effective approach for growing large-scale, high-density, and well-patterned conical boron nitride nanorods. A catalyst layer of Fe (NO3) 3 was patterned on a silicon substrate by using a copper grid as a mask. The nanorods were grown via annealing milled boron carbide powders at 1300 &deg;C in a flow of nitrogen gas. The as-grown nanorods exhibit uniform morphology and the catalyst pattern precisely defines the position of nanorod deposition. Cathodoluminescence (CL) spectra of the nanorods show two broad emission bands centered at 3.75 and 1.85 eV. Panchromatic CL images reveal clear patterned structure. &copy; 2006 American Institute of Physics.
Chen, P.P.T., Butcher, K.S.A., Wintrebert-Fouquet, M., Wuhrer, R., Phillips, M.R., Prince, K.E., Timmers, H., Shrestha, S.K. & Usher, B.F. 2006, 'Apparent band-gap shift in InN films grown by remote-plasma-enhanced CVD', JOURNAL OF CRYSTAL GROWTH, vol. 288, no. 2, pp. 241-246.
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Veal, T.D., Piper, L.F.J., Phillips, M.R., Zareie, M.H., Lu, H., Schaff, W.J. & McConville, C.F. 2006, 'Scanning tunnelling spectroscopy of quantized electron accumulation at InxGa1-xN surfaces', PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, vol. 203, no. 1, pp. 85-92.
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Coleman, V.A., Buda, M., Tan, H.H., Jagadish, C., Phillips, M.R., Koike, K., Sasa, S., Inoue, M. & Yano, M. 2006, 'Observation of blue shifts in ZnO/ZnMgO multiple quantum well structures by ion-implantation induced intermixing', Semiconductor Science and Technology, vol. 21, no. 3, pp. L25-L28.
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Implantation with low-energy (80 keV) oxygen ions and subsequent rapid thermal annealing at 800 &deg;C are used to induce intermixing in a stack of 19 ZnO/Zn0.7Mg0.3O multiple quantum wells grown on sapphire by molecular beam epitaxy. Large blue shifts of more than 300 meV have been observed for doses up to 1 1016 cm-2, with no observation of saturation. This process is driven by the creation of defects by implantation which encourage the diffusion of Mg from the barrier layers into the ZnO quantum wells. Although defects are introduced during the implantation process, good recovery of the cathodoluminescence is seen following rapid thermal annealing. The Zn-Mg interdiffusion in this system has also been calculated for the corresponding ion doses, and the diffusion coefficient extracted. This study has significant implications for band gap engineering of ZnO/ZnMgO optoelectronic devices. &copy; 2006 IOP Publishing Ltd.
Zareie, H.M., McDonagh, A.M., Edgar, J., Ford, M.J., Cortie, M.B. & Phillips, M.R. 2006, 'Controlled assembly of 1,4-phenylenedimethanethiol molecular nanostructures', Chemistry of Materials, vol. 18, no. 9, pp. 2376-2380.
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We present here the first high-resolution scanning tunneling microscope images showing that 1,4-phenylenedimethanethiol forms mono- and multilayers on gold(111) substrates under particular solution-deposition conditions. The high-resolution images show that the deposition conditions strongly influence the type of surface structure formed. The molecular structures were also probed using molecular-etching techniques and through deposition and imaging of gold nanoparticles. The current-voltage (I-V) characteristics of the multilayer structures are significantly different from those of monolayers. For the first time, scanning electron microscopy experiments were used to investigate the homogeneity of larger surface areas of the surface structures. &copy; 2006 American Chemical Society.
Coleman, V.A., Bradby, J.E., Jagadish, C. & Phillips, M.R. 2006, 'Observation of enhanced defect emission and excitonic quenching from spherically indented ZnO', Applied Physics Letters, vol. 89, no. 8.
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The influence of spherical nanoindentation on the band edge and deep level emission of single crystal c-axis ZnO has been studied by cathodoluminescence (CL) spectroscopy and monochromatic imaging. Excitonic emission is quenched at the indent site and defect emission in the range of 450-720 nm is enhanced. Analysis of CL monochromatic images and spectra suggests that at least two different defect states are responsible for the broad defect emission band. Additionally, the indents result in a strong crystallographic dependence of the defect emission, producing a rosette feature with [112?0] [21?1?0], and [12?10] orientations that reflect the star-shaped luminescence quenching observed at the excitonic peak (390 nm). &copy; 2006 American Institute of Physics.
Phillips, M.R. 2006, 'Cathodoluminescence microscopy and spectroscopy of opto-electronic materials', Microchimica Acta, vol. 155, no. 1-2, pp. 51-58.
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Cathodoluminescence (CL) microscopy and spectroscopy are enabling techniques for the microcharacterisation of technologically important materials. Recent advances in SEM instrumentation have considerably expanded the microanalytical capabilities of the CL technique. In this paper, following a brief overview of the principles and practice of CL microscopy and spectroscopy, a number of examples are presented that demonstrate the utility of the technique for the microcharacterisation of advanced opto-electronic materials.
Pauc, N., Phillips, M.R., Aimez, V. & Drouin, D. 2006, 'Carrier diffusion processes near threading dislocations in GaN and GaN : Si characterized by low voltage cathodoluminescence', SUPERLATTICES AND MICROSTRUCTURES, vol. 40, no. 4-6, pp. 557-561.
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Morgan, S.W. & Phillips, M.R. 2006, 'Transient analysis of gaseous electron-ion recombination in the environmental scanning electron microscope', JOURNAL OF MICROSCOPY-OXFORD, vol. 221, pp. 183-202.
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Morgan, S.W. & Phillips, M.R. 2006, 'Gaseous scintillation detection and amplification in variable pressure scanning electron microscopy', JOURNAL OF APPLIED PHYSICS, vol. 100, no. 7.
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Godlewski, M., Phillips, M.R., Kazlauskas, K., Czernecki, R., Targowski, G., Perlin, P., Leszczynski, M., Figge, S. & Hommel, D. 2006, 'Profiling of light emission of GaN-based laser diodes with cathodoluminescence', PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, vol. 203, no. 7, pp. 1811-1814.
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Malguth, E., Hoffmann, A., Gehlhoff, W., Gelhausen, O., Phillips, M.R. & Xu, X. 2006, 'Structural and electronic properties of Fe3+ and Fe2+ centers in GaN from optical and EPR experiments', PHYSICAL REVIEW B, vol. 74, no. 16.
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Phillips, M. & Drouin, D. 2006, 'Comparison of Low Voltage Cathodoluminescent Phosphors', Microscopy & Microanalysis, vol. 12, no. S2, pp. 1526-1527.
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Phillips, M., Drouin, D. & Goldys, E.M. 2006, 'Probing Carrier Behavior at the Nanoscale in Gallium Nitride using Low Voltage Cathodoluminescence', Microscopy & Microanalysis, vol. 12, no. S2, pp. 156-157.
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McBean, K.E., Phillips, M.R. & Goldys, E.M. 2006, 'Synthesis and characterization of doped and undoped ZnO nanostructures', Microscopy and Microanalysis, vol. 12, no. 4, pp. 327-330.
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Zinc oxide (ZnO) nanoparticles have been produced using precipitation methods from ethanolic solution. Rare-earth metal doping was performed, and the effect of lithium codoping on the luminescence properties of the rare-earth doped products was assessed. The resulting particles were characterized using cathodoluminescence and scanning electron microscopy. It was found that lithium significantly enhanced the cathodoluminescence signal from the rare-earth ions, which has been attributed to the increased integration of the rare-earth ions into the ZnO structure. The nanophase ZnO products were also annealed in argon, hydrogen, and oxygen, with hydrogen being the most successful for removing the broad defect emission present in as-grown samples and enhancing the ZnO near band edge emission. &copy; Microscopy Society of America 2006.
White, R., Phillips, M.R., Thomas, P. & Wuhrer, R. 2006, 'In-situ investigation of discolouration processes between historic oil paint pigments', Microchimica Acta, vol. 155, no. 1-2, pp. 319-322.
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Discolouring interactions between paint pigments have been observed since the mid 19th century. The source of some of these discolourations is the production of copper sulfides from an interaction between cadmium sulfide pigments and copper containing pigments. In this work, the discolouring interaction between cadmium yellow and malachite pigments was observed dynamically using the environmental scanning electron microscope (ESEM).
White, R.E., Thomas, P.S., Phillips, M.R. & Wuhrer, R. 2005, 'A DSC study of the effect of lead pigments on the drying of cold pressed linseed oil', Journal of Thermal Analysis and Calorimetry, vol. 80, no. 1, pp. 237-239.
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Cold pressed linseed oil and paints prepared using the inorganic pigments; lead white and red lead, were characterized using non-isothermal differential scanning calorimetry (DSC) in an air atmosphere to determine the effect of the pigment on the oxidative polymerisation of the drying oil medium. For each paint sample, the onset temperature for oxidation was reduced from 166&deg;C to the range 50 to 60&deg;C when a heating rate of 5 K min-1 was used. In order to determine the rate of drying, the non-isothermal experiments were carried out using a range of heating rates. A change in the mechanism oxidative polymerization was observed as the heating rate was increased. &copy; 2005 Akad&eacute;miai Kiad&oacute;, Budapest.
Scott, K., Butcher, A., Wintrebert-Fouquet, M., Chen, P.P.T., Wuhrer, R. & Phillips, M.R. 2005, 'Revisiting electrochromism in InN', Physica Status Solidi C: Conferences, vol. 2, no. 7, pp. 2293-2296.
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We confirm changes to the band-gap of InN thin films treated in an electrochemical cell in which water electrolysis is evident. Electrical properties of the films were also affected. It is suggested that the change in the film resistivity results from hydrogen incorporation or removal during the electrolysis (dependent on sample polarity). The presence of grain boundaries is believed to enhance the penetration of chemical species into the InN resulting in a greater net change in the observed properties. &copy; 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Scott, K., Butcher, A., Wintrebert-Fouquet, M., Chen, P.P.T., Prince, K.E., Timmers, H., Shrestha, S.K., Shubina, T.V., Ivanov, S.V., Wuhrer, R., Phillips, M.R. & Monemar, B. 2005, 'Non-stoichiometry and non-homogeneity in InN', Physica Status Solidi C: Conferences, vol. 2, no. 7, pp. 2263-2266.
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It is shown that the wide variation of apparent band-gap observed for thin films nominally referred to as InN is strongly influenced by variations in the nitrogen:indium stoichiometry. InN samples grown by remote plasma enhanced chemical vapour deposition show a change in band-gap between 1.8 and 1.0 eV that is not due to the Moss-Burstein effect, oxygen inclusion or quantum size effects, but for which changes in the growth temperature result in a strong change in stoichiometry. Material non-homogenity and non-stoichiometry appear to be general problems for InN growth. Excess nitrogen can be present at very high levels and indium rich material is also found. This work shows that the extent of the Moss-Burstein effect will have to be reassessed for InN. &copy; 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Godlewski, M., Ivanov, V.Y., Lusakowska, E., Bozek, R., Miasojedovas, S., Jursenas, S., Kazlauskas, K., Zukauskas, A., Goldys, E.M., Phillips, M.R., Bottcher, T., Figge, S. & Hommel, D. 2005, 'Influence of n-type doping on light emission properties of GaN layers and GaN-based quantum well structures', E-MRS 2004 Fall Meeting Symposia C and F, vol. 2, no. 3, pp. 1056-1059.
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Tomaszewska-Grzeda, A., Lojkowski, W., Godlewski, M., Yatsunenko, S., Drozdowicz-Tomsia, K., Goldys, E.M. & Phillips, M.R. 2005, 'Growth and characterization of ZnO nanoparticles', ACTA PHYSICA POLONICA A, vol. 108, no. 5, pp. 897-902.
Godlewski, M., Phillips, M.R., Czernecki, R., Targowski, G., Perlin, P., Leszczynski, M. & Figge, S. 2005, 'Light emission properties of GaN-based laser diode structures', ACTA PHYSICA POLONICA A, vol. 108, no. 4, pp. 675-680.
Godlewski, M., Yatsunenko, S., Ivanov, V.Y., Khachapuridze, A., Swiatek, K., Goldys, E.M., Phillips, M.R., Klar, P.J. & Heimbrodt, W. 2005, 'Origin of ultrafast component of photoluminescence decay in nanostructures doped with transition metal or rare-earth ions', ACTA PHYSICA POLONICA A, vol. 107, no. 1, pp. 65-74.
Wojcik, A., Kopalko, K., Godlewski, M., Lusakowska, E., Guziewicz, E., Minikayev, R., Paszkowicz, W., Swiatek, K., Klepka, M., Jakiela, R., Kiecana, M., Sawicki, M., Dybko, K. & Phillips, M.R. 2005, 'Thin films of ZnO and ZnMnO by atomic layer epitaxy', OPTICA APPLICATA, vol. 35, no. 3, pp. 413-417.
Mokkapati, S., Lever, P., Tan, H.H., Jagadish, C., McBean, K.E. & Phillips, M.R. 2005, 'Controlling the properties of InGaAs quantum dots by selective-area epitaxy', APPLIED PHYSICS LETTERS, vol. 86, no. 11.
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Drozdowicz-Tomsia, K., Goldys, E.M., Motlan, M., Zareie, H. & Phillips, M.R. 2005, 'Growth-temperature-dependent cathodoluminescence properties of GaSb/GaAs quantum-dot multilayer structures', Applied Physics Letters, vol. 86, no. 17, pp. 1-3.
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Multilayer GaSb/GaAs quantum-dot (QD) structures grown by atmospheric-pressure metalorganic chemical vapor deposition on semi-insulating GaAs (100) substrates with varying growth temperature of the confinement layers are studied by the cathodoluminescence (CL). Two main features assigned to wetting layer and QDs are observed in the CL spectra. Their relative positions strongly depend on the growth conditions of the confinement layers. The highest separation of 270 meV is achieved for GaAs confinement layers grown at 540 &deg;C. &copy; 2005 American Institute of Physics.
Godlewski, M., Yatsunenko, S., Drozdowicz-Tomsia, K., Goldys, E.M., Phillips, M.R., Klar, P.J. & Heimbrodt, W. 2005, 'Dynamics of light emission in CdMnS nanoparticles', ACTA PHYSICA POLONICA A, vol. 108, no. 4, pp. 681-688.
Godlewski, M., Lusakowska, E., Bozek, R., Goldys, E.M., Phillips, M.R., Bottcher, T., Figge, S. & Hommel, D. 2004, 'Cathodoluminescence and atomic force microscopy study of n-type doped GaN epilayers', PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, vol. 201, no. 2, pp. 212-215.
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Godlewski, M., Goldys, E.M., Phillips, M., Böttcher, T., Figge, S., Hommel, D., Czernecki, R., Prystawko, P., Leszczynski, M., Perlin, P., Grzegory, I. & Porowski, S. 2004, 'In-depth and in-plane profiling of light emission properties of InGaN-based laser diode', Physica Status Solidi A-Applied Research, vol. 201, pp. 207-211.
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Guziewicz, E., Godlewski, M., Kopalko, K., Lusakowska, E., Dynowska, E., Guziewicz, M., Godlewski, M.M. & Phillips, M. 2004, 'Atomic layer deposition of thin films of ZnSe - structural and optical characterization', Thin Solid Films, vol. 446, no. 2, pp. 172-177.
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Thin films of sphalerite-type ZnSe were grown by atomic layer deposition (ALD) from elemental Zn and Se precursors. These films, grown on various substrates, show bright blue `edge emission accompanied by donoracceptor pair emissions in the blue, green and red spectral regions. Red, green and blue emissions mixed together give a white color, with a color temperature between 2400 and 4500 K depending on a layer thickness and temperature. ZnSe grown by ALD is in consequence a promising material for the fabrication of semiconductor-based white light emitting thin film electroluminescence displays.
Gelhausen, O., Phillips, M.R., Goldys, E.M., Paskova, T., Monemar, B., Strassburg, M. & Hoffmann, A. 2004, 'Dissociation of H-related defect complexes in Mg-doped GaN', PHYSICAL REVIEW B, vol. 69, no. 12.
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Gelhausen, O., Malguth, E., Phillips, M.R., Goldys, E.M., Strassburg, M., Strassburg, M., Hoffmann, A., Graf, T., Gjukic, M. & Stutzmann, M. 2004, 'Doping-level-dependent optical properties of GaN:Mn', Applied Physics Letters, vol. 84, no. 22, pp. 4514-4516.
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Cathodoluminescence (CL) and optical transmission spectroscopy were used to study the optical properties of molecular-beam-epitaxy (MBE) grown GaN with different doping levels. The 1-?m-thick samples were grown by plasma-induced MBE on c-plane Al 2O 3 substrate. The absorption measurements were performed at 2 K with a 250 W tungsten-halogen lamp. The CL measurements showed that Mn-doping concentrations around 10 20 cm -3 reduced the near band edge emission intensity by around one order of magnitude.
Phillips, M.R., Zareie, M.H., Gelhausen, O., Drago, M., Schmidtling, T. & Richter, W. 2004, 'Scanning tunneling and cathodoluminescence spectroscopy of indium nitride', JOURNAL OF CRYSTAL GROWTH, vol. 269, no. 1, pp. 106-110.
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Godlewski, M., Lusakowska, E., Goldys, E.M., Phillips, M.R., Bottcher, T., Figge, S., Hommel, D., Prystawko, P., Leszcynski, M., Grzegory, I. & Porowski, S. 2004, 'Diffusion length of carriers and excitons in GaN-influence of epilayer microstructure', APPLIED SURFACE SCIENCE, vol. 223, no. 4, pp. 294-302.
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Godlewski, M., Yatsunenko, S., Khachapuridze, A., Ivanov, V.Y., Golacki, Z., Karczewski, G., Bergman, P.J., Klar, P., Heimbrodt, W. & Phillips, M.R. 2004, 'Mechanism of intra-shell recombination of transition metal and rare earth ions in nanostructures of II-VI compounds', JOURNAL OF ALLOYS AND COMPOUNDS, vol. 380, no. 1-2, pp. 45-49.
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Godlewski, M., Szmidt, J., Olszyna, A., Werbowy, A., Lusakowska, E., Phillips, M.R., Goldys, E.M. & Sokolowska, A. 2004, 'Luminescent properties of wide bandgap materials at room temperature', E-MRS 2003 FALL MEETING, SYMPOSIA A AND C, PROCEEDINGS, vol. 1, no. 2, pp. 213-218.
Kopalko, K., Godlewski, M., Lusakowska, E., Paszkowicz, W., Domagala, J.Z., Szczerbakow, A., Ivanov, V.Y., Godlewski, M.M. & Phillips, M.R. 2004, 'Monocrystalline ZnO films grown by atomic layer epitaxy - growth and characterization', 11TH INTERNATIONAL CONFERENCE ON II-VI COMPOUNDS (II-VI 2003), PROCEEDINGS, pp. 892-895.
Kopalko, K., Godlewski, M., Guziewicz, E., Lusakowska, E., Paszkowicz, W., Domagala, J., Dynowska, E., Szczerbakow, A., Wojcik, A. & Phillips, M.R. 2004, 'Monocrystalline thin films of ZnSe and ZnO grown by atomic layer epitaxy', VACUUM, vol. 74, no. 2, pp. 269-272.
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Strassburg, M., Rodina, A., Dworzak, M., Haboeck, U., Krestnikov, I.L., Hoffmann, A., Gelhausen, O., Phillips, M.R., Alves, H.R., Zeuner, A., Hofmann, D.M. & Meyer, B.K. 2004, 'Identification of bound exciton complexes in ZnO', PHYSICA STATUS SOLIDI B-BASIC RESEARCH, vol. 241, no. 3, pp. 607-611.
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Phillips, M.R., Gelhausen, O. & Goldys, E.M. 2004, 'Cathodoluminescence properties of zinc oxide nanoparticles', PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, vol. 201, no. 2, pp. 229-234.
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Gelhausen, O., Klein, H.N., Phillips, M.R. & Goldys, E.M. 2003, 'Low-energy electron-beam irradiation and yellow luminescence in activated Mg-doped GaN', APPLIED PHYSICS LETTERS, vol. 83, no. 16, pp. 3293-3295.
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Dredge, P., Wuhrer, R. & Phillips, M.R. 2003, 'Monet's painting under the microscope', MICROSCOPY AND MICROANALYSIS, vol. 9, no. 2, pp. 139-143.
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Godlewski, M., Guziewicz, E., Kopalko, K., Lusakowska, E., Dynowska, E., Godlewski, M.M., Goldys, E.M. & Phillips, M.R. 2003, 'Origin of white color light emission in ALE-grown ZnSe', JOURNAL OF LUMINESCENCE, vol. 102, pp. 455-459.
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Godlewski, M.M., Ivanov, V., Goldys, E.M., Phillips, M., Böttcher, T., Figge, S., Hommel, D., Czernecki, R., Prystawko, P., Leszczynski, M., Perlin, P., Grzegory, I. & Porowski, S. 2003, 'Cathodoluminescence profiling of InGaN-based quantum well sturctures and laser diodes - in-plane instabilities of light emission', ACTA Physica Polonica, vol. 103, no. 6, pp. 689-694.
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Gelhausen, O., Phillips, M.R. & Goldys, E.M. 2003, 'A method to improve the light emission efficiency of Mg-doped GaN', Journal of Physics D: Applied Physics, vol. 36, no. 23, pp. 2976-2979.
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Scanning cathodoluminescence (CL) spectroscopy and imaging were used to study the effect of post-growth processing on the CL efficiency of metal-organic vapour phase epitaxy-grown Mg-doped GaN. In this work, two treatments, thermal annealing in high-purity gaseous atmospheres (N2, O2 and H2(5%)/N2) and low-energy electron beam irradiation (LEEBI), have been investigated. Post-growth annealing in a H2/N2 atmosphere followed by LEEBI leads to a significant enhancement of the free electron-to-bound Mg-acceptor (e, Mg) CL emission and a reduction of nonradiative centres involving native defects. The presented results demonstrate that the combination of post-growth annealing in a H2/N2 atmosphere and LEEBI dissociation of Mg-H complex acceptors significantly improves the light emitting efficiency of Mg-doped p-type GaN. Conversely, the samples annealed in a N2 or O2 atmosphere exhibit a reduced (e, Mg) emission after both annealing and LEEBI treatment.
Yatsunenko, S., Khachapuridze, A., Ivanov, V., Godlewski, M.M., Khoi, L., Golacki, Z., Karczewski, G., Goldys, E.M., Phillips, M., Klar, P.J. & Heimbrodt, W. 2003, 'Spin dependent interactions of free carriers and manganese ions in nanostructures of wide band gap II-Mn-VI semiconductors - mechanism of lifetime reduction', ACTA Physica Polonica, vol. 103, no. 6, pp. 643-648.
Based on the results of optically detected magnetic resonance and time-resolved investigations we relate the observed lifetime shortening of intra-shell Mn2+ emission to spin dependent magnetic interactions between localized spins of Mn2+ ions and spins/magnetic moments of free carriers. We show that this mechanism is active in both bulk and in low dimensional structures, such as quantum wells, quantum dots, and nanostructures.
Gelhausen, O., Klein, H.N., Phillips, M.R. & Goldys, E.M. 2003, 'Electron irradiation-induced electro-migration and diffusion of defects in Mg-doped GaN', PHYSICA STATUS SOLIDI B-BASIC RESEARCH, vol. 239, no. 2, pp. 310-315.
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Phillips, M.R., Telg, H., Kucheyev, S.O., Gelhausen, O. & Toth, M. 2003, 'Cathodoluminescence efficiency dependence on excitation density in n-type gallium nitride', MICROSCOPY AND MICROANALYSIS, vol. 9, no. 2, pp. 144-151.
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Gelhausen, O., Klein, H.N., Phillips, M.R. & Goldys, E.M. 2002, 'Influence of low-energy electron beam irradiation on defects in activated Mg-doped GaN', APPLIED PHYSICS LETTERS, vol. 81, no. 20, pp. 3747-3749.
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Bradby, J.E., Kucheyev, S.O., Williams, J.S., Wong-Leung, J., Swain, M.V., Munroe, P., Li, G. & Phillips, M.R. 2002, 'Indentation-induced damage in GaN epilayers', Applied Physics Letters, vol. 80, no. 3, pp. 383-385.
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The mechanical deformation of wurtzite GaN epilayers grown on sapphire substrates is studied by spherical indentation, cross-sectional transmission electron microscopy (XTEM), and scanning cathodoluminescence (CL) monochromatic imaging. CL imaging of indents which exhibit plastic deformation (based on indentation data) shows an observable "footprint" of deformation-produced defects that result in a strong reduction in the intensity of CL emission. Multiple discontinuities are observed during loading when the maximum load is above the elastic-plastic threshold, and such a behavior can be correlated with multiple slip bands revealed by XTEM. No evidence of pressure-induced phase transformations is found from within the mechanically damaged regions using selected-area diffraction patterns. The main deformation mechanism appears to be the nucleation of slip on the basal planes, with dislocations being nucleated on additional planes on further loading. XTEM reveals no cracking or delamination in any of the samples studied for loads of up to 250 mN. &copy; 2002 American Institute of Physics.
Kucheyev, S.O., Toth, M., Phillips, M.R., Williams, J.S., Jagadish, C. & Li, G. 2002, 'X-ray spectrometry investigation of electrical isolation in GaN', JOURNAL OF APPLIED PHYSICS, vol. 91, no. 6, pp. 3940-3942.
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Kucheyev, S.O., Toth, M., Phillips, M.R., Williams, J.S., Jagadish, C. & Li, G. 2002, 'Chemical origin of the yellow luminescence in GaN', JOURNAL OF APPLIED PHYSICS, vol. 91, no. 9, pp. 5867-5874.
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Remond, G., Nockolds, C., Phillips, M. & Roques-Carmes, C. 2002, 'Implications of polishing techniques in quantitative X-ray microanalysis', Journal of Research of the national Institute of Standards and technology, vol. 107, no. 6, pp. 639-662.
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Toth, M., Phillips, M.R., Craven, J.P., Thiel, B.L. & Donald, A.M. 2002, 'Electric fields produced by electron irradiation of insulators in a low vacuum environment', JOURNAL OF APPLIED PHYSICS, vol. 91, no. 7, pp. 4492-4499.
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Toth, M., Phillips, M.R., Thiel, B.L. & Donald, A.M. 2002, 'Electron imaging of dielectrics under simultaneous electron-ion irradiation', JOURNAL OF APPLIED PHYSICS, vol. 91, no. 7, pp. 4479-4491.
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Godlewski, M., Goldys, E.M., Phillips, M., Bottcher, T., Figge, S., Hommel, D., Czernecki, R., Prystawko, P., Leszczynski, M., Perlin, P., Wisniewski, P., Suski, T., Bockowski, M., Grzegory, I. & Porowski, S. 2002, 'Relationship between sample morphology and carrier diffusion length in GaN thin films.', Acta Physica Polonica A, vol. 102, no. 4-5, pp. 627-630.
Scanning and spot-mode cathodoluminescence investigations of homo- and hetero-epitaxial GaN films indicate a surprisingly small influence of their microstructure on overall intensity of a light emission. This we explain by a correlation between structural quality of these films and diffusion length of free carriers and excitons. Diffusion length increases with improving structural quality of the samples, which, in turn, enhances the rate of nonradiative recombination on structural defects, such as dislocations.
Gauvin, R., Griffin, B., Nockolds, C., Phillips, M. & Joy, D.C. 2002, 'A method to measure the effective gas path length in the environmental or variable pressure scanning electron microscope', Scanning, vol. 24, no. 4, pp. 171-174.
A simple method is described to determine the effective gas path length when incident electrons scatter in the gas above the specimen. This method is based on the measurement of a characteristic x-ray line emitted from a region close to the incident beam. From various experimental measurements performed on various microscopes, it is shown that the efefctive gas path length may increase with the chamber pressure and that it is also often dependent on the type of x-ray bullet.
Remond, G., Myklebust, R.L., Fialin, M., Nockolds, C., Phillips, M. & Roques-Carmes, C. 2002, 'Decomposition of wavelength dispersive X-ray spectra', Journal of Research of the national Institute of Standards and technology, vol. 107, no. 6, pp. 509-529.
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Bradby, J.E., Kucheyev, S.O., Williams, J.S., Jagadish, C., Swain, M.V., Munroe, P. & Phillips, M.R. 2002, 'Contact-induced defect propagation in ZnO', Applied Physics Letters, vol. 80, no. 24, pp. 4537-4539.
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Contact-induced damage has been studied in single-crystal (wurtzite) ZnO by cross-sectional transmission electron microscopy (XTEM) and scanning cathodoluminescence (CL) monochromatic imaging. XTEM reveals that the prime deformation mechanism in ZnO is the nucleation of slip on both the basal and pyramidal planes. Some indication of dislocation pinning was observed on the basal slip planes. No evidence of either a phase transformation or cracking was observed by XTEM in samples loaded up to 50 mN with an ?4.2 ?m radius spherical indenter. CL imaging reveals a quenching of near-gap emission by deformation-produced defects.Both XTEM and CL show that this comparatively soft material exhibits extensive deformation damage and that defects can propagate well beyond the deformed volume under contact. Results of this study have significant implications for the extent of contact-induced damage during fabrication of ZnO-based (opto)electronic devices. &copy; 2002 American Institute of Physics.
Godlewski, M., Goldys, E.M., Butcher, K.S.A., Phillips, M.R., Pakula, K. & Baranowski, J.M. 2001, 'Cathodoluminescence investigations of interfaces in InGaN/GaN/sapphire structures', PHYSICA STATUS SOLIDI B-BASIC RESEARCH, vol. 228, no. 1, pp. 179-182.
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Kucheyev, S.O., Toth, M., Phillips, M.R., Williams, J.S., Jagadish, C. & Li, G. 2001, 'Cathodoluminescence depth profiling of ion-implanted GaN', Applied Physics Letters, vol. 78, no. 1, pp. 34-36.
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Cathodoluminescence (CL) spectroscopy shows that even relatively low-dose keV light-ion bombardment (corresponding to the generation of ?5 1019 vacancies/cm3) of wurtzite GaN results in a dramatic quenching of visible CL emission. Postimplantation annealing at temperatures up to 1050&deg;C generally causes a partial recovery of measured CL intensities. However, CL depth profiles indicate that, in most cases, such a recovery results from CL emission from virgin GaN, beyond the implanted layer due to a reduction in the extent of light absorption within the implanted layer. In this case, CL emission from the implanted layer remains completely quenched even after such an annealing. These results show that an understanding of the effects of ion bombardment and postimplantation annealing on luminescence generation and light absorption is required for a correct interpretation of luminescence spectra of GaN optically doped by keV ion implantation. &copy; 2001 American Institute of Physics.
Danilatos, G.D., Phillips, M.R. & Nailon, J.V. 2001, 'Electron beam current loss at the high-vacuum-high-pressure boundary in the environmental scanning electron microscope', Microscopy and Microanalysis, vol. 7, no. 5, pp. 397-406.
A significant loss in electron probe current can occur before the electron beam enters the specimen chamber of an environmental scanning electron microscope (ESEM). This loss results from electron scattering in a gaseous jet formed inside and downstream (above) the pressure-limiting aperture (PLA), which separates the high-pressure and high-vacuum regions of the microscope. The electron beam loss above the PLA has been calculated for three different ESEMs, each with a different PLA geometry: an ElectroScan E3, a Philips XL30 ESEM, and a prototype instrument. The mass thickness of gas above the PLA in each case has been determined by Monte Carlo simulation of the gas density variation in the gas jet. It has been found that the PLA configurations used in the commercial instruments produce considerable loss in the electron probe current that dramatically degrades their performance at high chamber pressure and low accelerating voltage. These detrimental effects are minimized in the prototype instrument, which has an optimized thin-foil PLA design.
Gelhausen, O., Phillips, M.R. & Toth, M. 2001, 'Depth-resolved cathodoluminescence microanalysis of near-edge emission in III-nitride thin films', JOURNAL OF APPLIED PHYSICS, vol. 89, no. 6, pp. 3535-3537.
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Cooper, R., Smith, K.L., Colella, M., Vance, E.R. & Phillips, M. 2001, 'Optical emission due to ionic displacements in alkaline earth titanates', Journal of Nuclear Materials, vol. 289, no. 1-2, pp. 199-203.
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Optical emission spectra in the 300-700 nm range were collected from single crystal CaTiO3, SrTiO3 and BaTiO3, and polycrystalline CaTiO3 samples, that were irradiated at room temperature using a Febetron 706 variable energy pulsed-electron-beam generator. The long-lived emissions (up to microseconds after the electron pulse) consist of broad (halfwidths to approximately 100 nm) bands centred around 380, 425, and 445 nm for CaTiO3, SrTiO3 and BaTiO3, respectively. These emission bands are similar to cathodoluminescence emissions from 25 keV electron irradiation attributed by others to direct conduction-valence band transitions in unreduced samples and oxygen vacancies in reduced samples. CaTiO3, SrTiO3 and BaTiO3 all have emission thresholds of 0.26&plusmn;0.02 MeV. This corresponds to a threshold displacement energy for oxygen, Ed of 45&plusmn;4 eV.
Godlewski, M., Mackowski, S., Karczewski, G., Goldys, E.M. & Phillips, M.R. 2001, 'Cathodoluminescence studies of self-organized CdTe/ZnTe quantum dot structure grown by MBE: in-plane and in-depth properties of the system', SEMICONDUCTOR SCIENCE AND TECHNOLOGY, vol. 16, no. 6, pp. 493-496.
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Godlewski, M., Goldys, E.M., Phillips, M.R., Pakula, K. & Baranowski, J.M. 2001, 'Cathodoluminescence and depth-profiling cathodoluminescence studies of interface properties in MOCVD-grown InGaN/GaN/sapphire structures: role of GaN buffer layer', APPLIED SURFACE SCIENCE, vol. 177, no. 1-2, pp. 22-31.
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Kucheyev, S.O., Toth, M., Phillips, M.R., Williams, J.S. & Jagadish, C. 2001, 'Effects of excitation density on cathodoluminescence from GaN', APPLIED PHYSICS LETTERS, vol. 79, no. 14, pp. 2154-2156.
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Buyanova, I.A., Chen, W.M., Goldys, E.M., Phillips, M.R., Xin, H.P. & Tu, C.W. 2001, 'Strain relaxation in GaNxP1-x alloy: effect on optical properties', PHYSICA B-CONDENSED MATTER, vol. 308, pp. 106-109.
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Godlewski, M., Goldys, E.M. & Phillips, M.R. 2000, 'Cathodoluminescence studies of in-plane and in-depth properties of GaN epilayers', JOURNAL OF LUMINESCENCE, vol. 87-9, pp. 1155-1157.
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Godlewski, M., Goldys, E.M., Phillips, M.R., Langer, R. & Barski, A. 2000, 'Cathodoluminescence depth-profiling studies of GaN/AlGaN quantum-well structures', JOURNAL OF MATERIALS RESEARCH, vol. 15, no. 2, pp. 495-501.
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Toth, M., Kucheyev, S.O., Williams, J.S., Jagadish, C., Phillips, M.R. & Li, G. 2000, 'Imaging charge trap distributions in GaN using environmental scanning electron microscopy', Applied Physics Letters, vol. 77, no. 9, pp. 1342-1344.
We present direct experimental evidence for a field assisted component in images acquired using the gaseous secondary electron detector (GSED) employed in environmental scanning electron microscopes. Enhanced secondary electron (SE) emission was observed in GSED images of epitaxial GaN bombarded with MeV He ions. The increase in SE emission is attributed to an electric field generated by electrons trapped at defects produced by ion implantation. The presence of nonradiative recombination centers and of trapped charge in implanted GaN was established by cathodoluminescence spectroscopy and energy dispersive x-ray spectrometry. The field assisted SE component is distinguishable from the "normal" GSED signal by characteristic pressure and temperature dependencies. The presented results demonstrate the utility of the GSED for imaging charge trap distributions in semiconductors. &copy; 2000 American Institute of Physics.
Toth, M. & Phillips, M.R. 2000, 'The effects of space charge on contrast in images obtained using the environmental scanning electron microscope', SCANNING, vol. 22, no. 5, pp. 319-325.
Masens, C., Schulte, J., Phillips, M. & Dligatch, S. 2000, 'Ultra flat gold surfaces for use in chemical force microscopy: Scanning probe microscopy studies of the effect of preparation regime on surface morphology', MICROSCOPY AND MICROANALYSIS, vol. 6, no. 2, pp. 113-120.
Toth, M., Phillips, M. & Griffin, B. 2000, 'X-ray Microanalysis of Insulators in the ESEM', Microscopy & Microanalysis, vol. 6, no. 2, pp. 786-787.
Godlewski, M., Goldys, E. & Phillips, M. 2000, 'Cathodoluminescence Studies of in-plane and in-depth Properties of GaN Epilayers', Journal of Luminescence, vol. 87-89, pp. 1155-1157.
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Phillips, M. 2000, 'Optical and structural properties of thin films of ZnS grown by atomic layer epitaxy', Journal of Wide Bandgap Materials, vol. 9, no. 1-2, pp. 55-63.
Whittall, A., Phillips, M. & Suetsugu, Y. 2000, 'Cathodoluminescence Emission For Differentiating The Degree Of Carbonation In Apatites', Bioceramics, vol. 0, pp. 179-182.
Cathodoluminescence has recently been used successfully in detecting and determining the spatial location of the amorphous phase in plasma sprayed calcium phosphate coatings. The aim of this study is to determine whether this same technique can be used t
Meier, T., Koch, S., Phillips, M. & Wang, H. 2000, 'Strong Coupling Of Heavy- And Light-hole Excitons Induced By Many-body Correlations', Physical Review B, vol. 62, no. 19, pp. 12605-12608.
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The differential absorption of a GaAs single quantum well is studied for resonant pumping at either the heavy- or light-hole exciton resonances using different polarization configurations. For all excitation conditions the observed spectra show bleaching
Kucheyev, S.O., Bradby, J.E., Williams, J.S., Jagadish, C., Toth, M., Phillips, M.R. & Swain, M.V. 2000, 'Nanoindentation of epitaxial GaN films', APPLIED PHYSICS LETTERS, vol. 77, no. 21, pp. 3373-3375.
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Toth, M. & Phillips, M.R. 2000, 'The role of induced contrast in images obtained using the environmental scanning electron microscope', SCANNING, vol. 22, no. 6, pp. 370-379.
Phillips, M.R. & Ott, D.M. 2000, 'Crosstalk caused by nonideal output filters in WDM lightwave systems', IEEE PHOTONICS TECHNOLOGY LETTERS, vol. 12, no. 8, pp. 1094-1096.
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Toth, M. & Phillips, M. 2000, 'Space Charge Artefacts in ESEM Images: Shadowing and Contrast', Microscopy & Microanalysis, vol. 6, no. 2, pp. 775-775.
Toth, M. & Phillips, M.R. 1999, 'Detection of Cr impurities in GaN by room temperature cathodoluminescence spectroscopy', Applied Physics Letters, vol. 75, no. 25, pp. 3983-3985.
Trace levels of Cr impurities in epitaxial GaN grown on sapphire substrates were investigated using cathodoluminescence (CL) spectroscopy. CL emissions characteristic of Cr in an octahedral crystal field were observed from ?-Ga2O3 overlayers produced on GaN by post-growth thermal annealing in dry O2. Cr luminescence was also observed from the sapphire substrates, a likely source of the Cr contaminant. The presented results illustrate the use of ?-Ga2O3 overlayers as high sensitivity indicators of the presence of Cr in GaN. &copy; 1999 American Institute of Physics.
Phillips, M.R. & Ott, D.M. 1999, 'WDM lightwave system crosstalk by optical Kerr effect with polarisation-dependent loss', ELECTRONICS LETTERS, vol. 35, no. 20, pp. 1764-1765.
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Phillips, M.R., Toth, M. & Drouin, D. 1999, 'Depletion layer imaging using a gaseous secondary electron detector in an environmental scanning electron microscope', APPLIED PHYSICS LETTERS, vol. 75, no. 1, pp. 76-78.
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Toth, M., Fleischer, K. & Phillips, M.R. 1999, 'Electron beam induced impurity electro-migration in unintentionally doped GaN', MRS Internet Journal of Nitride Semiconductor Research, vol. 4, no. SUPPL. 1.
Electron beam induced electromigration of O N+ and H + impurities in unintentionally n-doped GaN was investigated using cathodoluminescence (CL) kinetics profiling, CL imaging of regions pre-irradiated with a stationary electron beam, and wavelength dispersive x-ray spectrometry (WDS). The presented results (i) illustrate induced impurity diffusion in wide bandgap semiconductors, (ii) provide experimental evidence for the (V Ga-O N) 2- model of yellow luminescence in GaN with low Si content 1, (iii) confirm the roles of O in frequently reported bound exciton and donor-acceptor pair emissions and (iv) suggest the involvement of O N+ and hydrogenated gallium vacancies in a blue emission in autodoped GaN.
Leon, R., Okuno, J.O., Lawton, R.A., Stevens-Kalceff, M., Phillips, M.R., Zou, J., Cockayne, D.J.H. & Lobo, C. 1999, 'Dislocation-induced changes in quantum dots: Step alignment and radiative emission', Applied Physics Letters, vol. 74, no. 16, pp. 2301-2303.
A new type of quantum dot (QD) alignment for an InGaAs/GaAs QD multilayered structure has been observed. In addition to two distinct types of InGaAs dot alignment in vicinal GaAs (001), an abrupt transition in QD sizes and concentrations was seen. This was accompanied by bright QD emission, even after formation of a dislocation array, and different behaviors with thermal intermixing.
Fleischer, K., Toth, M., Phillips, M.R., Zou, J., Li, G. & Chua, S.J. 1999, 'Depth profiling of GaN by cathodoluminescence microanalysis', APPLIED PHYSICS LETTERS, vol. 74, no. 8, pp. 1114-1116.
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Phillips, M. & Wang, H. 1999, 'Coherent Oscillation In Four-wave Mixing Of Interacting Excitons', Solid State Communications, vol. 111, no. 6, pp. 317-321.
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We report the observation of quantum beat-like oscillations in transient four-wave mixing (FWM) of heavy-hole and light-hole excitonic transitions that share no common upper or lower states. Theoretical analysis shows that these oscillations arise from p
Toth, M., Fleischer, K. & Phillips, M.R. 1999, 'Direct experimental evidence for the role of oxygen in the luminescent properties of GaN', Physical Review B - Condensed Matter and Materials Physics, vol. 59, no. 3, pp. 1575-1578.
We present experimental evidence of electron-beam-induced diffusion of O and H in unintentionally doped n-type GaN grown on a sapphire substrate. Impurity diffusion was investigated using cathodoluminescence kinetics and imaging at 4 and 300 K and by wavelength dispersive x-ray analysis. The results illustrate the significance of electron-beam-induced electromigration in wide band gap semiconductors, confirm the roles of ON. in bound exciton, donor-acceptor pair and yellow emissions and suggest the involvement of ON. and hydrogenated gallium vacancies in the previously unexplained blue luminescence. &copy;1999 The American Physical Society.
Kim, D.G., Seong, T.Y., Baik, Y.J., Kalceff, M.A.S. & Phillips, M.R. 1999, 'Cathodoluminescence of diamond films grown on pretreated Si(001) substrates by microwave plasma chemical vapour deposition', DIAMOND AND RELATED MATERIALS, vol. 8, no. 2-5, pp. 712-716.
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Phillips, M.R. & Ott, D.M. 1999, 'Crosstalk due to optical fiber nonlinearities in WDM CATV lightwave systems', JOURNAL OF LIGHTWAVE TECHNOLOGY, vol. 17, no. 10, pp. 1782-1792.
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Godlewski, M., Goldys, E.M., Phillips, M.R., Langer, R. & Barski, A. 1998, 'Influence of the surface morphology on the yellow and "edge" emissions in wurtzite GaN', APPLIED PHYSICS LETTERS, vol. 73, no. 25, pp. 3686-3688.
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Gross, K.A., Gross, K.A., Gross, K.A. & Phillips, M.R. 1998, 'Identification and mapping of the amorphous phase in plasma-sprayed hydroxyapatite coatings using scanning cathodoluminescence microscopy', Journal of Materials Science: Materials in Medicine, vol. 9, no. 12, pp. 797-802.
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The presence and distribution of the amorphous phase is a key factor in the performance and bone-bonding behavior of plasma-sprayed hydroxyapatite coatings. Microanalysis of coatings was conducted with microprobe Raman and scanning cathodoluminescence microscopy. It was confirmed that the darker regions in polished cross sections represent the amorphous phase. The more intense cathodoluminescence emission from the amorphous phase during electron-beam irradiation compared with the crystalline phase was used to detect the two structurally different areas within the sample. By selecting the peak of the emission at 450 nm it was possible to raster the surface with the electron beam and produce a map of the amorphous phase in polished sections, a fracture surface and an as-sprayed surface of the plasma-sprayed coating. Cathodoluminescence microscopy, based on the different light emission from the amorphous phase and hydroxyapatite, is a useful tool for identifying and mapping of the amorphous-phase constituent in plasma-sprayed coatings.
Toth, M. & Phillips, M.R. 1998, 'Monte Carlo modeling of cathodoluminescence generation using electron energy loss curves', Scanning, vol. 20, no. 6, pp. 425-432.
This work demonstrates the validity of approximating cathodoluminescence generation throughout the electron interaction volume by the total electron energy loss profile. The energy loss profiles in multilayer specimens were accurately calculated using the Monte Carlo simulation CASINO. Resolution of cathodoluminescence images can be estimated from the electron beam spot diameter, the electron penetration range, and the minority carrier diffusion length.
Szczerbakow, A., Godlewski, M., Dynowska, E., Ivanov, V.Y., Swiatek, K., Goldys, E.M. & Phillips, M.R. 1998, 'Structure, surface morphology and optical properties of thin films of ZnS and CdS grown by atomic layer epitaxy', ACTA PHYSICA POLONICA A, vol. 94, no. 3, pp. 579-582.
Goldys, E.M., Zuo, H.Y., Tansley, T.L., Phillips, M.R. & Contessa, C.M. 1998, 'Band offsets in In0.15Ga0.85As/GaAs and In0.15Ga0.85As/Al0.15Ga0.85As studied by photoluminescence and cathodoluminescence', SUPERLATTICES AND MICROSTRUCTURES, vol. 23, no. 6, pp. 1223-1226.
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Goldys, E.M., Zuo, H.Y., Phillips, M.R., Contessa, C.M., Vaughan, M.R. & Tansley, T.L. 1997, 'Type I and type II alignment of the light hole band in In0.15Ga0.85As/GaAs and in In0.15Ga0.85As/Al0.15Ga0.85As strained quantum wells', JOURNAL OF ELECTRONIC MATERIALS, vol. 26, no. 8, pp. 922-927.
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Kalceff, M.A.S., Phillips, M.R., Moon, A.R. & Smallwood, A. 1997, 'Cathodoluminescence microanalysis of natural hydrated amorphous SiO2; Opal', PHYSICS AND CHEMISTRY OF MINERALS, vol. 24, no. 2, pp. 131-138.
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Wuhrer, R., Yeung, W.Y., Phillips, M.R. & McCredie, G. 1996, 'Study on dc magnetron sputter deposition of titanium aluminium nitride thin films: Effect of aluminium content on coating', THIN SOLID FILMS, vol. 290, pp. 339-342.
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Stevens Kalceff, M.A., Phillips, M.R. & Moon, A.R. 1996, 'Electron irradiation-induced changes in the surface topography of silicon dioxide', Journal of Applied Physics, vol. 80, no. 8, pp. 4308-4314.
The irradiation of crystalline (?-SiO2) and amorphous (?-SiO2) silicon dioxide with a stationary electron beam produces characteristic changes in the surface topography. The development of these changes has been investigated using cathodoluminescence spectroscopy and microscopy, scanning probe (atomic force) microscopy, and scanning electron microscopy. Electron irradiation produces a permanent volume increase on (crystalline) ?-SiO2, while in (amorphous) ?-SiO2 an initial small volume increase is followed by volume loss as irradiation continues. The observed changes are consistent with electromigration of oxygen under the influence of the electric field induced by charge trapping at preexisting or irradiation-induced defects. Oxygen enrichment may produce expansion of the surface region due to the formation of peroxy linkage defects. In ?-SiO2, charges trapped by defects at grain boundaries produce enhanced electric fields which may result in volume reduction at the surface, when critical field strengths are exceeded. The observed volume reductions may be attributed to electron stimulated desorption of constituents, in particular oxygen mass loss, and densification of the surface region associated with the formation of oxygen-deficient defect centers. &copy; 1996 American Institute of Physics.
Ariyavisitakul, S., Darcie, T.E., Greenstein, L.J., Phillips, M.R. & Shankaranarayanan, N.K. 1996, 'Performance of simulcast wireless techniques for personal communication systems', IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, vol. 14, no. 4, pp. 632-643.
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Kim, Y., Kim, Y., Yuan, S., Leon, R., Jagadish, C., Gal, M., Johnston, M.B., Phillips, M.R., Stevens Kalceff, M.A., Zou, J. & Cockayne, D.J.H. 1996, 'Effects of anodic oxide induced intermixing on the structural and optical properties of quantum wire structure grown on nonplanar GaAs substrate', Journal of Applied Physics, vol. 80, no. 9, pp. 5014-5020.
Effects of anodic oxide induced intermixing on the structural and optical properties of stacked GaAs quantum wire (QWR) structures grown on a sawtooth-type nonplanar GaAs substrate are investigated. Cross-sectional transmission electron microscope (XTEM) observation, temperature dependent photoluminescence (PL) and cathodoluminescence (CL) imaging were used. Intermixing was achieved by pulsed anodic oxidation of the GaAs cap layer and subsequent rapid thermal annealing, was verified by XTEM analysis. A significant enhancement of QWR PL is observed accompanied by a notable blueshift of the sidewall quantum well (SQWL) PL due to the intermixing. Furthermore, an extended necking region is observed after the intermixing by spatially resolved CL. The temperature dependence of the PL intensities of both SQWL and QWR show maxima at approximately T ?110 K indicating the role of the extended necking region in feeding carriers to SQWL and QWR. &copy; 1996 American Institute of Physics.
KALCEFF, M.A.S. & PHILLIPS, M.R. 1995, 'CATHODOLUMINESCENCE MICROCHARACTERIZATION OF THE DEFECT STRUCTURE OF QUARTZ', PHYSICAL REVIEW B, vol. 52, no. 5, pp. 3122-3134.
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ZHOU, B., LI, X., TANSLEY, T.L., BUTCHER, K.S.A. & PHILLIPS, M.R. 1995, 'GROWTH OF GAN FILMS BY COMBINED LASER AND MICROWAVE PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION', JOURNAL OF CRYSTAL GROWTH, vol. 151, no. 3-4, pp. 249-253.
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Stevens Kalceff, M.A. & Phillips, M.R. 1995, 'Electron irradiation induced outgrowths from quartz', Journal of Applied Physics, vol. 77, no. 8, pp. 4125-4127.
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The irradiation of natural and ultrapure synthetic crystalline quartz by a stationary electron beam produces surface outgrowths, which have been analyzed using scanning electron microscopy, atomic force microscopy, cathodoluminescence spectroscopy, and microscopy. Oxygen enrichment of the quartz surface occurs due to electromigration resulting from the trapped charge induced electric field. It is proposed that the accumulated oxygen is incorporated into the quartz surface structure as peroxy linkages, the formation of which results in the permanent volume increase observed as amorphous outgrowths on crystalline quartz. A cathodoluminescence emission at 2.3 eV localized on the outgrowths, is attributed to an intrinsic process. &copy; 1995 American Institute of Physics.
MOON, A.R. & PHILLIPS, M.R. 1994, 'DEFECT CLUSTERING AND COLOR IN FE,TI-ALPHA-AL2O3', JOURNAL OF THE AMERICAN CERAMIC SOCIETY, vol. 77, no. 2, pp. 356-367.
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FRIGO, N.J., PHILLIPS, M.R. & BODEEP, G.E. 1993, 'CLIPPING DISTORTION IN LIGHTWAVE CATV SYSTEMS - MODELS, SIMULATIONS, AND MEASUREMENTS', JOURNAL OF LIGHTWAVE TECHNOLOGY, vol. 11, no. 1, pp. 138-146.
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Pillai, S., Xu, Z., Gal, M., Glaisher, R., Phillips, M. & Cockayne, D. 1992, 'Cathodoluminescence From Porous Silicon', Japanese Journal Of Applied Physics Part 2-letters, vol. 31, no. 12A, pp. 1-2.
Spatially resolved cathodoluminescence (CL) spectra were measured on porous silicon. The CL spectra showed bands and prominent peaks ranging in energy between 1.45 eV and 3 eV and were unlike the photoluminescence spectra measured on the same samples, wh
PHILLIPS, M.R. & DARCIE, T.E. 1991, 'NUMERICAL-SIMULATION OF CLIPPING-INDUCED DISTORTION IN ANALOG LIGHTWAVE SYSTEMS', IEEE PHOTONICS TECHNOLOGY LETTERS, vol. 3, no. 12, pp. 1153-1155.
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Moon, A.R. & Phillips, M.R. 1991, 'Titania precipitation in sapphire containing iron and titanium', Physics and Chemistry of Minerals, vol. 18, no. 4, pp. 251-258.
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Titania, TiO2, precipitation in natural blue sapphire (Fe, Ti: ?-Al2O3) has been investigated using high resolution and analytical transmission electron microscopy. The structure and habit of the TiO2 precipitate depends on both the Ti4+ concentration and the temperature at which the precipitate formed. Tetragonal TiO2 (Rutile) grows at 1350&deg; C but at 1150&deg; C an orthorhombic non-equilibrium TiO2 polymorph precipitates. Both TiO2 polymorphs nucleate in the (0001)s plane as lens shaped discs twinned along their diameter. The crystallographic alignment of each type of TiO2 precipitate with respect to the ?-Al2O3 host matrix provides a high degree of structural coherency with minimal lattice mismatch. Electron diffraction analysis established the following precipitate/host orientation relationships: tetragonal TiO2: {011}r{norm of matrix} {11 {Mathematical expression}07B;100}r{norm of matrix}(0001)s and ?01 {Mathematical expression}?r?10 {Mathematical expression}0?s twinned along the (011)r planeand orthorhombic TiO2: {021}?{norm of matrix}{11 {Mathematical expression}0}s, {100}?{norm of matrix}(0001)s and ?0 {Mathematical expression}2? ?{norm of matrix}?10 {Mathematical expression}0?s twinned along the (021)? plane. &copy; 1991 Springer-Verlag.
MOON, A.R. & PHILLIPS, M.R. 1991, 'ACCURATE OH BOND ANGLE DETERMINATION IN TRIGONAL CRYSTALS', APPLIED SPECTROSCOPY, vol. 45, no. 6, pp. 1051-1053.
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PHILLIPS, M.R., DARCIE, T.E., MARCUSE, D., BODEEP, G.E. & FRIGO, N.J. 1991, 'NONLINEAR DISTORTION GENERATED BY DISPERSIVE TRANSMISSION OF CHIRPED INTENSITY-MODULATED SIGNALS', IEEE PHOTONICS TECHNOLOGY LETTERS, vol. 3, no. 5, pp. 481-483.
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McCredie, G.M., Phillips, M.R. & Moon, A.R. 1991, 'Optimization of thinning rates in an argon ion beam thinner', Review of Scientific Instruments, vol. 62, no. 7, pp. 1855-1856.
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A simple and inexpensive ''feedback'' circuit has been devised that regulates the gas flow in an argon ion gun system and thus optimizes the specimen thinning rate. The circuit is easily adapted to suit a broad range of similar applications.
Moon, A.R. & Phillips, M.R. 1991, 'Defect clustering in H,Ti:?-Al2O3', Journal of Physics and Chemistry of Solids, vol. 52, no. 9, pp. 1087-1099.
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In order to investigate the defect structure of Ti:?-Al2O3, protons were incorporated into aluminium oxide single crystals doped with tetravalent titanium. This produced a set of sharp bands in the i.r. spectrum with stretching frequencies around 3300 cm-1, characteristic of OH bands. The thermal behaviour of these bands was investigated in a series of isochronal and isothermal heating experiments, monitored using FTIR spectroscopy. The i.r. spectra consisted of three main absorption bands at 3309cm-1, 3232cm-1 and 3187cm-1. The i.r. band at 3309cm-1 has been assigned to a (Ti. AlV'''AlOH. oTi. Al)x defect cluster. The lower energy bands at 3232cm-1 and 3187cm-1 were assigned to two structural variants of a (Ti. AlV'''AlOH. o)' defect cluster. The (Ti. AlV'''AlOH. oTi. Al)x defect cluster forms via the following reversible internal diffusion-limited association reaction Ti. Al + (Ti. AlV'''AlOH. o)' ? (Ti. AlV'''AlOH. o)x. The binding enthalpy for this reaction was determined to be 1.06 &plusmn; 0.20 eV. The clustering reaction was observed to follow first order reaction kinetics. An activation energy of 2.5 &plusmn;0.1 eV was determined for the (Ti. AlV'''AlOH. o)' cluster. The relative concentration of all charged and neutral defect associates was found to critically depend on the thermal history of the crystal. The defect structure of Ti4+:?-Al2O3 is also discussed with reference to this study. &copy; 1991.
MOON, A.R. & PHILLIPS, M.R. 1991, 'IRON AND SPINEL PRECIPITATION IN IRON-DOPED SAPPHIRE', JOURNAL OF THE AMERICAN CERAMIC SOCIETY, vol. 74, no. 4, pp. 865-868.
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MOON, A.R., PHILLIPS, M.R. & BLAIR, D.G. 1990, 'EQUILIBRATION IN DEFECT CLUSTERING REACTIONS', SOLID STATE COMMUNICATIONS, vol. 76, no. 7, pp. 881-882.
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MOON, A.R. & PHILLIPS, M.R. 1984, 'AN ELECTRON-MICROSCOPY STUDY OF EXSOLVED PHASES IN NATURAL BLACK AUSTRALIAN SAPPHIRE', MICRON AND MICROSCOPICA ACTA, vol. 15, no. 3, pp. 143-146.
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