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Dr Cuong Ton-That


Cuong Ton-That obtained a BSc in Physics (Honours, University Medal) from UTS and a PhD degree in the field of surface science from the Robert Gordon University, UK in 2000. He joined UTS in 2003 as a lecturer. Prior to working at UTS, he was a postdoctoral research associate in the Nanoscience Centre, University of Cambridge from 2000-2003.

His research is focused upon the development of oxide materials and nanostructures for solid state lighting applications. He has expertise in the growth and characterisation of zinc oxide nanostructures together with experience in cathodoluminescence, synchrotron-based X-ray spectroscopy, deep-level transient spectroscopy and scanning probe microscopy techniques.

He is currently the Leader of Research and Development in the School of Physics and Advanced Materials.

Image of Cuong Ton-That
Senior Lecturer, School of Physics and Advanced Materials
Program Director, School of Physics and Advanced Materials
Core Member, Research Strength Materials and Technology for Energy Efficiency Member
Research Fellow, Institute for Nanoscale Technology
Core Member, Research Strength Materials and Technology for Energy Efficiency Member
BSc (Hons) (UTS), PhD (Aberdeen)
+61 2 9514 2201
Can supervise: Yes


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.
Foley, M., Ton-That, C. & Phillips, M. 2010, 'Cathodoluminescence characterisation of vapour transport grown ZnO structures', Proceedings of the 2010 International Conference on Nanoscience and Nanotechnology, IEEE Explorer, Piscataway, NJ, U.S.A., pp. 207-209.
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ZnO structures grown under controlled vapourphase 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 influence.
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.
Foley, M., Ton-That, C. & Kirkup, L. 2007, 'Electrical Properties of Pure and Oxygen-Intercalated Fullerene Films', Proceedings of the 31st Annual Condensed Matter and Materials Meeting, Australian National University, ACT, Australia, pp. 1-3.
The conductivity of polycrystalline fullerene films as a function of oxygen concentration was investigated and found to be affected significantly by changes in oxygen partial pressure. The conductivity of the film was fitted to an Arrhenius curve. Analysis of the data indicated that a change of 0.11eV in activation energy occurred as the oxygen pressure was varied over two orders of magnitude.

Journal articles

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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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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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. 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
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, pp. 27150-27156.
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The influence of deep level surface defects on electrical and gas sensing properties of ZnO nanorods NH3(g) sensors was studied. ZnO nanorods 5060 nm in diameter were synthesized via low-temperature hydrothermal growth at 90 degrees 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 degrees 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 O-2 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.
Ton-That, C., Nguyen, T.-.P. & Dan, Y. 2013, 'Enhanced photoluminescence of polyfluorene by incorporation of Al-doped ZnO nanoparticles', Thin Solid Films, vol. 538, pp. 85-88.
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Photoluminescent and structural properties of nanocomposite films consisting of green-emitting polyfluorene (PF) and Al-doped ZnO (AZO) nanoparticles were investigated. Topographical analysis shows that AZO nanoparticles can be homogeneously dispersed in PF films with less than 10 wt.% AZO. Photoluminescence of the composite films was investigated under wavelength selective excitation of AZO. Photoexcitation with laser energy below the AZO bandgap produces a slight increase in the PF emission intensity with increasing AZO concentration, accompanied by a spectral blueshift. These effects are attributed to separation of polymer chains and twisting of the PF backbone as revealed by Raman spectroscopy. On the other hand, photoexcitation above the AZO bandgap shows a remarkable enhancement, with the intensity at 5-10 wt.% AZO being three times greater than that of pure PF. The luminescence enhancement is attributed to the efficient transfer of energy from AZO nanoparticles to PF. 2013 Elsevier B.V. All rights reserved.
Cortie, M.B., Coutts, M.J., Ton-That, C., Dowd, A., Keast, V.J. & McDonagh, A.M. 2013, 'On the coalescence of nanoparticulate gold sinter ink', Journal of Physical Chemistry C, vol. 117, no. 21, pp. 11377-11384.
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We examine the mechanism by which thiol-protected gold nanoparticle inks can sinter at surprisingly low temperatures. At room temperature the sample is comprised of randomly close-packed gold nanoparticles of about 2.3 nm diameter with a ligand shell of about 0.2 nm effective thickness. As the particles are heated through 80 C they begin to coarsen, reaching about 10 nm diameter at 180 C. Upon further heating, rapid sintering and grain growth occurs at a temperature that depends on environment and heating rate. Sintering in vacuum requires a higher temperature than in oxidizing environments. Mass spectrometry in the former case is consistent with volatile species such as C 4H9, C2SH, and C2H4 being displaced, whereas XPS shows that the exposed surface of the Au is rich in C and S. However, when sintering is performed in the presence of even trace O 2, it is the Au-S bond that is cleaved, and the sintering temperature is lowered by up to 50 C. In this case mass spectrometry shows the generation of alkane and thiol fragments, some S2 and H2S, and oxidized sulfur-containing species, whereas XPS shows that C and S on the Au surface is much reduced. 2013 American Chemical Society.
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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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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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, vol. 86, no. 11.
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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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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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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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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, pp. 670-671.
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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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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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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. 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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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 2008.
Ton-That, C., Foley, M. & Phillips, M.R. 2008, 'Luminescent properties of ZnO nanowires and as-grown ensembles.', Nanotechnology, vol. 19, no. 41, p. 415606.
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Vertically aligned ZnO nanowires were synthesized on a sapphire ([Formula: see text]) 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.
Ton-That, C., Dowd, A.R., Shard, A.G., Dhanak, V.R., Taninaka, A., Shinohara, H. & Welland, M.E. 2007, 'Electronic structure of potassium-doped La@C82 metallofullerene studied with photoelectron spectroscopy', Physical Review B, vol. 76, no. 16, pp. 1-7.
The electronic structure of potassium-doped La@C82 has been studied with synchrotron-radiation photoelectron spectroscopy. Ultraviolet photoemission measurements indicate evolution of the valence-band states of La@C82 with increasing potassium content, but KxLa@C82 remains semiconducting for all x between 0 and 6, with a band gap of at least 0.4 eV, in contrast to K-doped C60. The valence-band features, including those which arise from the interactions of C82 cages with La and K, show oscillatory behavior of photoemission intensity with incident photon energy. The strength of the oscillations varies between the states, and we associate diminished oscillations with increased localization of electron density. Finally, although core and valence states of La@C82 change considerably with potassium dosage, the encapsulated La atom is well shielded from the outside chemical environment and its valency remains close to 3+.
Ton-That, C., Welland, M.E., Larsson, J.A., Greer, J.C., Shard, A.G., Dhanak, V.R., Taninaka, A. & Shinohara, H. 2005, 'Electrostatic ordering of the lanthanum endoatom in La@C-82 adsorbed on metal surfaces', Physical Review B, vol. 71, no. 4, pp. 1-6.
An investigation of the dynamic behavior of the endohedral La atom in La@C-82 adsorbed on Ag(111) or Cu(111) using the normal-incidence x-ray standing wavefield (NIXSW) technique is presented. For the surface-normal (111) reflection, NIXSW demonstrates d
Shard, A.G., Ton-That, C., Campbell, P.A. & Dhanak, V.R. 2004, 'Site occupancy of chlorine on Cu(111) using normal-incidence x-ray standing waves: The energy difference between fcc and hcp hollow sites', Physical Review B, vol. 70, no. 15, pp. 155409-155417.
t has previously been established that the lowest energy site for chlorine atoms on Cu(111) is the ?fcc? hollow. However, substantial population of the ?hcp? hollow at room temperature indicates that there is a relatively small difference in energy between the two sites. We show that this energy difference must be less than 10 meV by measuring the relative populations using normal-incidence x-ray standing waves and comparing the results to Monte Carlo simulations. This result is consistent with recent density functional theory calculations which indicate an energy difference of approximately 5 meV
Ton-That, C., Shard, A.G., Egger, S., Dhanak, V.R. & Welland, M.E. 2003, 'Modulations of valence-band photoemission spectrum from C-60 monolayers on Ag(111)', Physical Review B, vol. 67, no. 15, pp. 1-6.
The photon-energy dependences of valence-band photoemission spectra have been investigated for monolayer, submonolayer, and multilayer C60 films on Ag(111). The intensity ratios of the highest and next-highest occupied molecular orbitals (the HOMO and NHOMO) of the films are found to oscillate with the same period as the incident photon energy is varied, but the amplitude of the oscillation is smaller with lower film coverage. Since the characteristics of the molecular orbitals of C60 in the monolayers are considerably different from those of the thick film due to the charge-transfer interaction between the metallic surface and the molecule the observation opposes the proposal in which the oscillation is entirely dependent on the nature of the empty and occupied states involved in the photoemission process. The results instead support the photoelectron interference model by Hasegawa et al. [Phys. Rev. B 58, 4927 (1998)]. Variation of the oscillation amplitude with C60 coverage is explained in terms of hybridization of the HOMO and NHOMO with the surface. Depositing C60 onto Ag(111) held at a high temperature produces a single-phase (2sqrt[3]2sqrt[3]) R30 C60 monolayer. Angle-resolved photoemission experiments reveal changes in the relative intensities of the two bands with the azimuth-emission angle, measured with respect to the symmetry axes of the ordered monolayer. The intensity modulation is due to anisotropic scattering of photoelectrons along various molecular axes.
Ton-That, C., Shard, A.G., Egger, S., Dhanak, V.R., Taninaka, A., Shinohara, H. & Welland, M.E. 2003, 'Orientation and constraints of endohedral lanthanum in La@C82 molecules adsorbed on Cu(111)', Physical Review B, vol. 68, no. 4, pp. 1-6.
The orientation of the endohedral La atom in La@C82 adsorbed on Cu(111) has been determined using the normal-incidence x-ray standing wave (NIXSW) technique. The NIXSW measurements were carried out using both the normal ?111? and 70.5 off-normal ?111? Bragg reflections. The La ?111? profiles of the La@C82 monolayer and submonolayers are found to be similar to the ?111? profile of the multilayer, while the ?111? profiles of the monolayer and submonolayers are distinctly different with much lower peak height. This indicates significant ordering of the La atoms in the monolayers with respect to height above the Cu surface but little lateral ordering. The results of curve fits to the monolayer profiles show that the La atoms are regionally located at 1.62 (0.77) above an extended scattering plane from the crystal. Cooling the monolayers to a temperature of 170 K increases ordering of the La atoms with respect to height above the surface. The NIXSW results demonstrate that the endohedral molecules adopt a restricted orientation upon adsorbing on the surface and the La atom resides on either the upper or lower half of the cage. Theoretical calculations show that the most stable La positions are located in the top half of the fullerene cage, which supports the La upper configuration. The results are explained in terms of electrostatic interactions between the endohedral atom, the fullerene cage, and the substrate.
Ton-That, C., Shard, A.G. & Bradley, R.H. 2002, 'Surface feature size of spin-cast PS/PMMA blends', Polymer, vol. 43, no. 18, pp. 4973-4977.
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Thin films of polystyrene (PS)/polymethylmethacrylate (PMMA) blends have been spin cast on mica from chloroform solutions. When the concentration of PMMA in the casting solution is less than that of PS a pitted morphology is formed. The average sizes of the pits are shown to increase with both the total concentration of the casting solution and the relative concentration of PMMA. The change in pit size is explained in terms of incomplete dewetting of a PMMA solution from an underlying PS solution. For a given ratio of PMMA/PS the average pit diameters appear to increase linearly with the square of the film thickness, the gradient of which is dependent on the film composition.
Teare, D.O., Emmison, N., Ton-That, C. & Bradley, R.H. 2001, 'Effects of Serum on the Kinetics of CHO Attachment to Ultraviolet-Ozone Modified Polystyrene Surfaces.', J Colloid Interface Sci, vol. 234, no. 1, pp. 84-89.
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Attachment kinetics of Chinese hamster ovarian (CHO) cells were investigated on ultraviolet-ozone oxidized polystyrene (UVO-PS) dishes in the presence and absence of serum. The surface chemistry of UVO-PS has been extensively characterized. Although cells attached rapidly to the oxidized dishes with serum present it was found that serum actually inhibits the rate of attachment. Spreading of attached cells was favored by the presence of serum. It is suggested that the increased quantity of hydrophilic carboxyl groups on longer exposed UVO-PS leads to a change in the protein layer adsorbed from serum and also a higher affinity of the surface for extracellular proteins secreted by the attached cells. The UVO-PS surfaces present a new way of producing tissue culture grade polystyrene (TCPS) in a highly controllable method, which would ensure greater consistency in TCPS surfaces. Copyright 2001 Academic Press.
Ton-That, C., Shard, A.G., Teare, D.O. & Bradley, R.H. 2001, 'XPS and AFM surface studies of solvent-cast PS/PMMA blends', Polymer, vol. 42, no. 3, pp. 1121-1129.
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Films of polystyrene (PS) and poly(methyl methacrylate) (PMMA) blends of two different thicknesses have been examined by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Blends with different compositions were spin-cast onto a mica substrate with chloroform as the mutual solvent. XPS measurements revealed surface enrichment of PMMA in all compositions. The thicker (66 nm) films exhibit a higher degree of PMMA surface enrichment than the thinner (17 nm) films. AFM imaging allows distinctions to be drawn between blends with differing compositions. The blend films with less than 50% PMMA bulk concentration generally exhibit pitted surfaces; the pit size varies with film thickness and bulk composition. When the PMMA bulk concentration is greater than 50%, the film surface changes to show island-like phase-separated structure. The surface segregation and morphology are explained in terms of solubilities of the two polymers in the solvent and dewetting of PMMA relative to PS. The phase domains on the film surface have also been resolved by frictional force microscopy (FFM) using hydrophilic tips bearing hydroxyl groups.
Ton-That, C., Teare, D.O. & Bradley, R.H. 2000, 'Friction, surface oxidation, and polar free energy for polymer surfaces by chemical force microscopy', Chemistry of Materials, vol. 12, pp. 2106-2111.
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Ricketts, B. & Ton-That, C. 2000, 'Self-discharge of carbon-based supercapacitors with organic electrolytes', Journal of Power Sources, vol. 89, pp. 64-69.
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Ton-That, C., Shard, A.G., Daley, R. & Bradley, R.H. 2000, 'Effects Of Annealing On The Surface Composition And Morphology Of PS/PMMA Blend', Macromolecules, vol. 33, no. 22, pp. 8453-8459.
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Films of polystyrene (PS) and poly(methyl methacrylate) (PMMA) blend have been annealed at a temperature above their glass transition temperatures for up to 48 h. Surface chemical compositions of the cast and annealed films were measured by X-ray photoelectron spectroscopy (XPS) while surface topographical changes were followed by atomic force microscopy (AFM). The blend films spin-cast from chloroform produce nonequilibrium surfaces with a significant excess of PMMA. The polymer component with a lower surface free energy, PS, is shown to segregate to the surface upon annealing. The PS surface concentration of the films, containing 50% PS:50% PMMA in the bulk, was evaluated using the ester peak in XPS C Is spectra (sampling depth similar to9 nm) and found to increase from similar to5% (freshly spin-cast film) to a saturated level of similar to 47% after 17 h of annealing. AFM imaging reveals evolution of blend morphology with annealing time. The spin-cast films prior to annealing exhibit pitted topography with typical pit size of similar to1.2 mum and depth of 30-40 nm. As the annealing process proceeds, these pits get continually shallower. Frictional force microscopy with hydroxylated tips recorded surface phase separations for the films of 2-4 h annealing. As the annealing continues to above 14 h, the pitted structure becomes distorted. The surface enrichment and morphology changes upon annealing are explained by dewetting of PMMA relative to PS.
Teare, D.O., Emmison, N., Ton-That, C. & Bradley, R.H. 2000, 'Cellular Attachment To Ultraviolet Ozone Modified Polystyrene Surfaces', Langmuir, vol. 16, no. 6, pp. 2818-2824.
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The surfaces of standard untreated polystyrene cell culture dishes have been oxidatively modified for up to 8 min exposure time using an ultraviolet ozone treater in order to promote cell adhesion. Surface oxygen chemisorption and topographical modification has been characterized using monochromatic X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The oxidation process is shown to proceed at low exposure times (<60 s) via the formation of C-OR groups, although some R2C=O and RO-C=O groups are also formed. At longer treatments, RO-C=O groups become the dominant species, although the other groups are also present. The maximum level of oxygen reached is 36 atomic 8. Some of the oxygen present at surfaces treated at times of >60 s is in the form of loosely bound low molecular weight oxidized material (LMWOM) which is produced by oxidative scission of the PS backbone. Water washing leads to a reduction in surface oxygen content mainly by the removal of RO-C=O and R2C=O functional groups. The residual stable oxygen levels, which can be introduced, are approximately 20-25 atomic %. Surface chemistry changes are accompanied by the formation of surface spikes which are about 30 nm high and 300-400 nm wide. A correlation between treatment time/oxygen level and overall roughness is observed. The effect of washing upon the topography is to slightly increase the surface roughness, although not to a significant degree. The attachment kinetics of adhesion for Chinese hamster ovary cells show that adhesion occurs much more rapidly for oxidized surfaces than for untreated control materials. A direct correlation between the levels of oxidation and the rate of cell adhesion is demonstrated.
Teare, D.O., Ton-That, C. & Bradley, R.H. 2000, 'Surface characterization and ageing of ultraviolet-ozone treated polymers using atomic force microscopy and x-ray photoelectron spectroscopy', Surface and Interface Analysis, vol. 29, no. 4, pp. 276-283.
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Ultraviolet-ozone (UVO) treatment of poly(ethyleneterephthalate) (PET) films and polystyrene (PS) dishes of up to 10 min exposure has been studied. Surface polarity, oxygen chemisorption and topographical change were analysed by contact angle measurement, x-ray photoelectron spectroscopy and atomic force microscopy. Studies of the treated surface reveal the chemistry behind the increasing oxygen content. The oxidation process is shown to proceed via different mechanisms for the two polymers. Polyethyleneterephthalate appears to undergo a Norrish-type chain depolymerization reaction, whereas PS undergoes a much more random chain scission attack. Atomic force microscopy analysis shows an increase in the surface roughness with increasing exposure to UVO for both polymers, with grains of low-molecular-weight oxidized material (LMWOM) forming at the surface. This material can be removed by washing. Surfaces that remain after washing have a higher concentration of oxygen species than the native surfaces. Analysis of aged surfaces shows that for oxidized PET a relaxation process occurs, lowering the levels of surface oxygen. This appears to occur due to the diffusion of LMWOM into the PET bulk. Relaxation of the oxidized PS surface is less thermodynamically favourable owing to the apolar nature of the PS
Ton-That, C., Shard, A.G. & Bradley, R.H. 2000, 'Thickness of spin-cast polymer thin films determined by angle-resolved XPS and AFM tip-scratch methods', Langmuir, vol. 16, no. 5, pp. 2281-2284.
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Polystyrene (PS) and poly(methyl methacrylate) (PMMA) thin films (<100 nm thickness) have been spin-cast from chloroform solution onto cleaved mica surfaces (roughness within 0.2 nm). An algorithm for calculating the film thicknesses based on the relative intensities of the C 1s peak of the films and the Si 2s peak of the mica from angle-resolved X-ray photoelectron spectroscopy (XPS) is presented. The film thickness changes as a function of casting conditions. Data from this approach are comparable with thickness measured by an atomic force microscopy (AFM) tip-scratch method in the range 1.5-5.5 nm. Thicknesses of the films are shown to increase linearly with concentration of cast solutions.
Ton-That, C., Teare, D.O., Campbell, P.A. & Bradley, R.H. 1999, 'Surface characterisation of ultrviolet-ozone treated PET using atomic force microscopy and x-ray photoelectron spectroscopy', Surface Science, vol. 435, pp. 278-282.
Kirkup, L. & Ton-That, C. 1998, 'A direct reading thermometer based on a silicon diode', Physics Education, vol. 33, pp. 302-305.