Browsing by Author "McKenzie, DR"

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    Cathodic arc co-deposition of highly oriented hexagonal Ti and Ti2AlC MAX phase thin films
    (Elsevier, 2009-08-25) Guenette, MC; Tucker, MD; Ionescu, M; Bilek, MMM; McKenzie, DR
    Ti2AlC belongs to a family of ternary nanolaminate alloys known as the MAX phases, which exhibit a unique combination of metallic and ceramic properties. Here we report pulsed cathodic arc deposition of c axis normal oriented Ti2AlC thin films on α-Al2O3 (001) single crystal substrates heated to 900°C, without an intentionally pre-deposited seed layer. Oriented hexagonal Ti is observed in some films and an in-plane epitaxial relationship between the α-Al2O3 (001) substrate, the hexagonal Ti and Ti2AlC MAX phase is observed. We observe formation of the Ti2AlC phase in all films despite variations in elemental composition. The electrical resistivity of our films was in the range 0.48–0.67 μΩ m, higher than other values found for Ti2AlC in the literature. © Elsevier B.V.
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    Depth-resolved structural and compositional characterization of ion-implanted polystyrene that enables direct covalent immobilization of biomolecules
    (Springer Link, 2015-06-03) Bilek, MMM; Kondyurin, A; Stephen, D; Steel, BC; Wilhelm, RA; René Heller, R; McKenzie, DR; Weiss, AS; James, M; Möller, W
    A polystyrene film spun onto polished silicon substrates was implanted with argon ions using plasma immersion ion implantation (PIII) to activate its surface for single-step immobilization of biological molecules. The film was subsequently investigated by X-ray and neutron reflectometry, ultraviolet (UV)–visible (vis) and Fourier transform infrared (FTIR) ellipsometry, FTIR and Raman spectroscopy, as well as nuclear reaction analysis to determine the structural and compositional transformations associated with the surface activation. The ion irradiation resulted in a significant densification of the carbon structure, which was accompanied by hydrogen loss. The density and hydrogen profiles in the modified surface layers were found to agree with the expected depths of ion implantation as calculated by the Stopping and Range of Ions in Matter (SRIM) software. The data demonstrate that the reduction in film thickness is due to ion-induced densification rather than the removal of material by etching. Characterization by FTIR, atomic force microscopy (AFM), ellipsometry, and X-ray reflectometry shows that polystyrene films modified in this way immobilize dense layers of protein (tropoelastin) directly from solution. A substantial fraction of the immobilized protein layer remains after rigorous washing with sodium dodecyl sulfate solution, indicating that its immobilization is by covalent bonding. © 2015, American Chemical Society.
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    Influence of gas entry point on plasma chemistry, ion energy and deposited alumina thin films in filtered cathodic arc
    (Springer, 2007-07-03) Rosen, J; Persson, POA; Ionescu, M; Pigott, J; McKenzie, DR; Bilek, MMM
    The effect of gas entry point on the plasma chemistry, ion energy distributions and resulting alumina thin film growth have been investigated for a d.c. cathodic arc with an aluminum cathode operated in an oxygen/argon atmosphere. Ions of aluminum, oxygen and argon, as well as ions originating from the residual gas are investigated, and measurements for gas entry at both the cathode and close to the substrate are compared. The latter was shown to result in higher ion flux, lower levels of ionised residual gas, and lower ion energies, as compared to gas inlet at the cathode. These plasma conditions that apply when gas entry at the substrate is used result in a higher film deposition rate, less residual gas incorporation, and more stoichiometric alumina films. The results show that the choice of gas entry point is a crucial parameter in thin film growth using reactive PVD processes such as reactive cathodic arc deposition. © 2007, Springer.
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    Oxygen incorporation in Ti2AlC thin films
    (American Institute of Physics, 2008-02-11) Rosen, J; Persson, POA; Ionescu, M; Kondyurin, A; McKenzie, DR; Bilek, MMM
    Thin films of Ti2AlC MAX phase have been deposited using a multiple cathode pulsed cathodic arc. Evidence for substantial oxygen incorporation in the MAX phase is presented, likely originating from residual gas present in the vacuum chamber during deposition. The characteristic MAX phase crystal structure is maintained, in agreement with ab initio calculations, supporting substitutional O in C lattice positions. On the basis of these results, we propose the existence of a MAX phase-like material with material properties tuned by the incorporation of oxygen. Additionally, possible unintentional O incorporation in previously reported MAX phase materials is suggested. © 2008, American Institute of Physics
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    Synthesis and characterisation of titanium vanadium nitride thin films
    (Australian Institute of Physics, 2005-01-31) Taylor, MB; Davies, KE; Gan, BK; McKenzie, DR; Bilek, MMM; McCulloch, DG; Latella, BA; Wilksch, PA; McPherson, M; Van den Brink, RA
    Many transition metal nitrides form very hard and wear resistant thin film coatings. Alloying of transition metal nitrides creates the possibility of producing films with even higher hardness and wear resistance. In this paper we look at alloying TiN and VN utilising a dual source pulsed cathodic arc. TiN and VN both form face centred cubic structures, have similar lattice parameters and are completely miscible over the entire range in bulk form . Of interest is the correlation between intrinsic stress, indentation hardness, microstructure and optical properties of Ti(1-x)VxN films over a range of compositions from x = 0 to x = 1. Previous work by Knotek [using magnetron sputtering showed that thin films of Ti(1-x)VxN made using a metal target of 25 atomic percent V and 75 atomic percent Ti showed the best wear resistance in a pin-on-disc test and the highest Vickers microhardness. In this work we vary the ratio of pulses applied to each cathode in the dual source filtered cathodic arc system to change the composition of the resultant film in a controllable manner. In this way, the properties over a range of composition can be evaluated. In addition to hardness, this work will explore the variations in optical properties of the alloys. Nitrides frequently exhibit attractive colours; for instance, the colour of TiN thin films deposited by plasma immersion ion implantation has been found to vary widely with the conditions of deposition. However, little has been published on the optical properties of the Ti(1-x)VxN alloy.