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Geoff McCredie

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Professional Officer & Workshop Manager, Technical Services Research
Professional Officer, Centre of Expertise Microstructural Analysis
+61 2 9514 7373


Smith, G., Gerritsen, S., Hossain, M. & McCredie, G. 2001, 'Plasmon-mediated visible and near infra red transmission through sub-30-nm holes in metal films: potential in solar energy applications', Solar and Switching Materials, Solar and Switching Materials, SPIE, San Diego, USA, pp. 29-38.
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The recent discovery that electromagnetic radiation can transmit super-efficiently through sub-wavelength holes in metal films and thin metal foils has implications for solar energy and energy efficiency technologies, especially thin metal films and metal particle arrays. The effect involves light induced surface plasmons coupling through the holes to form new states which can resonantly absorb and re-emit photons. They are a virtual bound state for photons. The material must have a dielectric constant below -1, and for noble metals enhancement is strong beyond (lambda) approximately 0.7 micrometers , with a long wavelength limit set by absorption losses, well into the black body spectral range. In aluminium the strong onset is in the visible. Thus control of solar heat gain and thermal radiation can utilize this effect. Broad band or narrow band spectral selectivity are possible, depending on metal thickness and how the holes are arranged with respect to each other. Very interesting effects occur in multilayers, with standard multilayer thin film optics not applying when this phenomena is present. An admittance approach to handling thin film optics in the presence of surface plasmon coupling is addressed.
Smith, G., Earp, A.A., Franklin, J. & McCredie, G. 2001, 'Novel high-performance scattering materials for use in energy saving light fittings and skylights based on polymer pigmented with polymer', Solar and Switching Materials, Solar and Switching Materials, SPIE, San Diego, pp. 10-18.
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Simple quantitative performance criteria are developed for translucent materials in terms of hemispherical visible transmittance, and angular spread of transmitted luminance using a half angle. Criteria are linked to applications in luminaires and skylights with emphasis on maximising visible throughput while minimising glare. These basic criteria are also extended to angle of incidence changes which are substantial. Example data is provided showing that acrylic pigmented with spherical polymer particles can have total hemispherical transmittance with weak thickness dependence, which is better than clear sheet, while the spread of transmitted light is quite thickness-sensitive and occurs over wider angles than inorganic pigments. This combination means significantly fewer lamps can achieve specified lux levels with low glare, and smaller skylights can provide higher, more uniform daylight illuminance.

Journal articles

Martin, A.A., McCredie, G. & Toth, M. 2015, 'Electron beam induced etching of carbon', Applied Physics Letters, vol. 107, no. 4.
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&copy; 2015 AIP Publishing LLC.Nanopatterning of graphene and diamond by low energy ( 30keV) electrons has previously been attributed to mechanisms that include atomic displacements caused by knock-on, electron beam heating, sputtering by ionized gas molecules, and chemical etching driven by a number of gases that include N<inf>2</inf>. Here, we show that a number of these mechanisms are insignificant, and the nanopatterning process can instead be explained by etching caused by electron induced dissociation of residual H<inf>2</inf>O molecules. Our results have significant practical implications for gas-mediated electron beam nanopatterning techniques and help elucidate the underlying mechanisms.
Samapisut, S., Heness, G.L., Tipparach, U. & McCredie, G. 2012, 'Effects of Magnetron Discharge Power and N2 Flow Rate for Preparation of TiCrN Thin Film', Procedia Engineering, vol. 32, pp. 1135-1138.
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Titanium Chromium Nitride (TiCrN) multilayer coatings on cutting tools, press molds and dies can be used to prolong their life cycle because of their superior corrosion and oxidation resistance. We investigated on three effecting conditions, the magnetron discharging powers of Ti and Cr targets and N2 flow rate. TiCrN multilayer coatings were prepared by dual DC magnetron sputtering. The crystallography and microstructure of the films were investigated by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystalline structures were obtained the cubic and mixed phases of Ti0.5Cr0.5N with the mean lattice parameters of a = b = c = 4.238 &Aring; and TiCrN2 with the mean lattice parameters of a = b = c = 4.1835 &Aring; for the condition of discharging powers on Ti and Cr target, respectively. However, the N2 flow rate condition, the orthorhombic oriented structure occurred with the mean lattice parameters of a = 2.962 &Aring;, b = 4.130 &Aring; and c = 2.875 &Aring;. The morphology of TiCrN thin films show the average grain size ~ 100200 nm, and the thickness of ~1 micron Cr-layer, ~0.5 micron CrN-layer and ~2 micron TiCrN-layer.
Ton-That, C., Foley, M., Lee Cheong Lem, L.O., McCredie, G., Phillips, M. & Cowie, B. 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 &micro;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.
Kirkup, L., Kalceff, W. & McCredie, G. 2007, 'Effect Of Injection Current On The Repeatability Of Laser Diode Junction Voltage-temperature Measurements', Journal Of Applied Physics, vol. 101, no. 2, pp. 1-6.
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The junction-voltage temperature relationship of a laser diode is used to determine the temperature of the device in the range -20 to 120 degrees C. We consider changes that occur to this relationship when the diode is driven at its nominal operating cur
Kirkup, L., Kalceff, W. & McCredie, G. 2006, 'System for measuring the junction temperature of a light emitting diode immersed in liquid nitrogen', Review Of Scientific Instruments, vol. 77, no. 4, pp. 1-3.
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A versatile system has been developed for the measurement under LABVIEW (TM) control of junction temperatures in a light emitting diode (LED). Measurements are reported on a commercially available high-intensity InGaAlP LED immersed in liquid nitrogen an
Solina, D.M., Cheary, R.W., Kalceff, W. & McCredie, G. 2005, 'X-ray reflectivity study of radio frequency sputtered silicon oxide on silicon', Thin Solid Films, vol. 489, no. 1-2, pp. 37-41.
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An X-ray reflectivity study carried out on 45-450 angstrom films of radio frequency sputtered silicon oxide on silicon, with particular attention given to the interface between film and substrate. In order to model refectivity data it was necessary to in
Liu, J., McCredie, G., Ford, M., Wieczorek, L. & Cortie, M.B. 2005, 'Investigation of the optical properties of hollow aluminium 'nano-caps'', Nanotechnology, vol. 16, no. 12, pp. 3023-3028.
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A colloidal suspension of hollow aluminium, cap-shaped nanoparticles ('nano-caps'_ can be conveniently produced by evaporation of aluminium onto a spin-coated layer of polystyrene nanoparticles (PSNPs), followed by sonication and dissolution of the polymer template. Although ordinary spherical aluminium nanoparticles have a plasmon resonance in the ultra-violet, the 'nano-caps' show plasmon absorption between 700 and 1200 nm due to their geometry. The position of their extinction peaks can be tuned by varying the thickness of the aluminium and the shape of the nano-cap. The optical properties of these shapes were modelled using the discrete dipole approximation method, which confirmed that the 'caps'have very significantly red-shifted absorbance and scattering compared to spheres. This finding suggests that aluminium nano-caps might compete with gold and silver nanoparticles in applciations requiring absorption in the near infrared.
Swift, P.D., Solina, D.M., Cheary, R.W. & McCredie, G. 2003, 'Investigation of the interfacial structure of ultra-thin platinum film deposited by cathodic-arc', Thin Solid Films, vol. 440, no. 1-2, pp. 117-122.
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Ultra-thin films are of interest in the production of X-ray mirrors that use a multilayer structure. The most commonly used deposition techniques are dc magnetron sputtering and electron beam evaporation; this paper presents results of cathodicarc deposition. Ultra thin films of platinum with nominal thicknesses in the range 1565 &Aring; were deposited on silicon substrates and the film structure investigated using X-ray reflectivity and X-ray photoelectron spectroscopy. It has been found that the structure of the deposited films consists of three layersthe platinum film, a silicon oxide layer and a platinum silicide layer. In contrast to dc magnetron and electron beam deposited films, the silicide layer of cathodicarc deposited films have a higher density and greater thickness, which is attributed to the higher energy process of this deposition technique. These attributes of the cathodicarc deposited films suggest that the deposition technique is not suitable for production of mirrors of materials that react with each other, but for materials that do not the deposition technique is potentially more favourable than that of e-beam and magnetron sputtering.
Wuhrer, R., McCredie, G. & Yeung, W.Y. 2003, 'On production of nanocrystalline ternary nitride coatings via magnetron sputtering', Materials Science Forum, vol. 426-4, pp. 2473-2478.
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Solina, D.M., Cheary, R.W., Swift, P.D. & McCredie, G. 2003, 'The fabrication of stable platinum-silicon oxide multilayers for X-ray mirrors', Thin Solid Films, vol. 423, no. 1, pp. 1-12.
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An investigation has been carried out to determine the conditions required for the fabrication of stable SiO2Pt multilayers using DC-magnetron sputtering for the Pt and RF-magnetron sputtering for the SiO2. As a preliminary investigation, single layers of Pt on SiO2 were analysed by X-ray reflectivity (XRR) and X-ray photoelectron spectroscopy (XPS) to develop a model of the PtSiO2 interface layer. The results indicated that a distinct interface layer develops as a Pt silicate approximately 6 &Aring; thick. SiO2Pt multilayers fabricated with a period d>65 &Aring; using pure argon as the sputtering gas, display X-ray reflectivity patterns which can be accurately characterised by a repeating bilayer model. When d<65 &Aring; the multilayer becomes unstable upon exposure to air. Additional peaks develop in the XRR pattern which increase in magnitude with time. These peaks arise from the expansion of the SiO2 layers in the multilayer starting from the top bilayer and gradually working through the multilayer. In the as-prepared specimens the SiO2 layers are incompletely oxidised and have a composition SiOx (x<2) and, on exposure to air, oxygen diffuses through the multilayer surface converting the SiOx to SiO2. By introducing a small partial pressure of oxygen into the sputtering gas during deposition, multilayers with d<65 &Aring; remained stable on exposure to air. Under these conditions the density of the platinum layers determined from XRR measurements was reduced by approximately 25%. XPS showed that the platinum layer contained bonded oxygen in the form of platinum oxide PtOx (x<1). SiO2/PtOx multilayers have been fabricated with periods down to 13 &Aring;, but the intensity of the first order peak drops off dramatically once the thickness of the PtOx layer is less that 1012 &Aring;.
Gan, B.K., Bilek, M.M., McKenzie, D.R., Swift, P.D. & McCredie, G. 2003, 'Optimizing the triggering mode for stable operation of a pulsed cathodic arc deposition system', Plasma Sources Science & Technology, vol. 12, no. 4, pp. 508-512.
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In order to deposit fine structures such as nanoscale multilayers using a pulsed cathodic arc, it is necessary to ensure that the deposition per pulse is stable over a large number of pulses. We compare the deposition rate using centre and edge triggering in a pulsed cathodic arc system by determining the rate of change of thickness of a growing film. Three arc currents were used and the results indicated that the centre triggering configuration provides a constant deposition rate when compared to edge triggering. It was also observed that the highest arc current in the centre mode showed the most uniform deposition rate. The erosion profile of the cathodes for the two different triggering types were examined and used to explain the differences in terms of uniformity of erosion. We also measured the discharge voltage and found that there was an increase with increasing arc current.
Smith, G., Green, D.C., McCredie, G., Hossain, M., Swift, P.D. & Luther, M.B. 2001, 'Optical Characterisation of Materials and Systems for Daylighting', Renewable Energy, vol. 22, pp. 85-90.
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The measurement of BRTF (Bi-directional rePectance and transmittance function) is described using a new instrument which is capable of supplying BRTF data and algorithms for use in computer simulations directly on diuse materials and indirectly on large samples and sub-systems. A high sensitivity and dynamic range is needed to achieve low minimum observable BRTF and the role of angular resolution are discussed with examples. Forward scattering with extended tails is found to dominate pigmented polycarbonate. Slatted blinds are discussed as examples of systems where azimuth is important.
Solina, D.M., Cheary, R.W., Swift, P.D., Dligatch, S., McCredie, G., Gong, B. & Lynch, P.A. 2000, 'Investigation of the Interfacial Structure of Ultra-Thin Platinum Films Using X-Ray Reflectivity ad X-ray Photoelectron Spectroscopy', Thin Solid Films, vol. 372, no. 0, pp. 94-103.
Ultra-thin films of platinum deposited on highly polished 100 silicon have been investigated using X-ray reflectivityXRR.and X-ray photoelectron spectroscopyXPS.as part of a study on the interface structure of multilayers used for X-ray mirrors. In this paper results are presented for films deposited by electron beam evaporation and by DC-magnetron sputtering. The reflectivity was fitted by assuming an intermediate platinum silicide layer exists between the platinum and the silicon. XPS data clearly confirmed the existence of such a platinum silicide layer. According to the XRR data this layer was estimated to be approximately 10 A&deg;thick for e-beam samples and approximately 30 A&deg;thick for magnetron samples. For e-beam films the fitted density for the platinum silicide layer was found to decrease from 16.4 g?cmy3 for a nominal 80 A&deg; film down to 2.65 g?cmy3 for a nominal 20 A&deg; film. For magnetron sputtered films the fitted density was always within the range of 6.1]6.8 g?cmy3. The fitted density of the platinum layer from the e-beam results was always within 5% of the density of bulk platinum whereas for the magnetron sputtered films the density decreased uniformly with decreasing film thickness for films with a nominal thickness less than 30 A&deg;. The XPS data show that the magnetron deposited platinum penetrates through the native oxide layer and into the silicon substrate to a far greater degree than the e-beam deposited platinum.
Smith, G., Earp, A.A., Stevens, J., Swift, P.D., McCredie, G. & Franklin, J. 2000, 'Materials Properties for Advanced Daylighting in Buildings', Sayish AAM, vol. 6, no. 1, pp. 201-206.
Some recent developments in materials used to illuminate interior and exterior spaces with daylight, and mathematical modelling of their interaction with light for design purposes are presented. The Sydney 2000 Olympic Stadium roof and a new solid light guide system are two examples. Emphasis is on making full use of the daylight resource, not just the diffuse component, while controlling the associated solar heat gain. Sensitivity to glare is essential if materials capabilities are to be realised.
Smith, G., Yan, W., Hossain, A.K. & McCredie, G. 1998, 'Science Of Daylighting In Buildings', Renewable Energy, vol. 15, no. 1-4, pp. 325-330.
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The materials characterisation requirements for accurate yet practical simulation of daylighting in buildings is examined for a range of emerging and existing technologies which seek to raise the contribution of daylighting to overall lighting requiremen
Wuhrer, R., Yeung, W.Y., Phillips, M. & McCredie, G. 1996, 'Study on D.C. magnetron sputter deposition of titanium aluminium nitride thin films: effect of aluminium content on coating', Thin Solid Films, vol. 290-291, pp. 339-342.
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Titanium aluminium nitride thin films have been deposited on glass slides using a dual unbalanced d.c. magnetron sputter arrangement with separate titanium and aluminium targets. A range of TiperAl/N compositions were produced by varying the aluminium ta
Kirkup, L., Kalceff, W. & McCredie, G. 1992, 'System For The Study Of Localized Heating At Current Contacts On Ceramic Superconductors', Measurement Science & Technology, vol. 3, no. 12, pp. 1141-1145.
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We present a versatile and sensitive system used to quantify the heating effect when pulsed and ramped transport currents are supplied to contacts made to high-T(c) superconductors. Measurements made with the system reveal that modest currents (of the or
McCredie, G., Phillips, M. & Moon, T. 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.