Browsing by Author "Comrie, Craig M"

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    Atomic mobility in thin solid Pa2Si films
    (1985) Zingu, Edmund Charles; Comrie, Craig M
    A theory for the growth kinetics of planar silicide formation in single- and bi-layer metal silicon systems has been developed on the basis that the chemical potential gradient in the growing layer is the driving force for diffusion. The predictions of the theory, when applied to single layer metal-silicon systems, is in agreement with other theories and with experimental results. Planar growth of the outer silicide layer in bilayer metal-silicon systems is predicted to proceed linearly with time, both when controlled by an interfacial reaction and when limited by diffusion through the interposed silicide layer (when this layer is sufficiently thick). In the latter case it is predicted that the growth rate of the outer silicide layer is inversely proportional to the thickness of the interposed layer.
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    Development of a plasma source ion implantation facility for the modification of materials' surfaces
    (2001) Meyer, Kevin Alan; Prozesky, Victor M; Comrie, Craig M; Alport, Michael J
    In Plasma Source Ion Implantation high energy [10-50 keV] plasma ions are implanted into materials to modify surface properties, achieving surface hardening, increased wear and corrosion resistance. Plasma Source Ion Implantation is alos used for doping semiconductors and could form an essential step in the manufacture of multilayered wafers. This thesis describes the development and construction of the plasma implantation facility at the Materials Research Group of the Naitonal Accelerator Centre; in particular, the development of the Plasma Assisted Materials Modification Laboratory, the analytical tools available at the Materials Research Group and surrounding universities, basic research into the implantation of steels, the x-rays emitted as a side-effect of plasma source ion implantation and the development of an analytical technique of interest to silicon wafer-cutting technologies.
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    Growth and characterisation of thin film superconductors on oxides, silicon and silicides
    (1994) Naidoo, R Y; Pretorius, R; Comrie, Craig M
    High Tc thin film superconductors are of great interest because of their potential applications, particularly in the microelectronics field. A successful superconductor microelectronic technology depends both on the ability to grow good quality superconducting thin films, and the need to incorporate these films into multilayer semiconductor devices. In this work the growth and characterisation of high Tc Y₁Ba₂Cu₃O₇ films by inverted cylindrical magnetron sputtering and pulsed ruby laser ablation on oxides, silicon and silicides is investigated. The inverted cylindrical magnetron sputter system has been effectively used to counter the problem of negative ion re-sputtering found in sputter deposition of oxide films. The optimal growth conditions for both these techniques have been determined. Rutherford backscattering spectrometry is used to obtain thickness and stoichiometry information, while X-ray diffraction gave phase and orientational data. Ion channeling was used for structural analysis and Auger electron spectroscopy was used to determine the homogeneity of the films.
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    Laser induced epitaxy of Ni and Co silicides
    (1995) Schroeder, Brett Robert; Comrie, Craig M
    Laser annealing of metal layers on silicon substrates failed to produce uniform silicide layers. This can be attributed to constitutional supercooling effects. Laser annealing of thermally grown monosilicides gave low (~5%) minimum yields for Co and Ni on <111> substrates1 as well as Ni on <100> substrates. The best yield achieved for Co on <100> substrates is 35%. The formation of a non-equilibrium epitaxial monosilicide was also achieved. Numerical calculations based on a heat flow approach gave fair quantitative agreement with experiment.
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    Marker studies of nickel silicide formation
    (1988) McLeod, John Edward; Comrie, Craig M; Pretorius, R
    Atomic diffusion during the solid state formation of thin films of nickel silicides (Ni2Si and NiSi) from nickel and amorphous silicon has been investigated using 31Si radioactive tracer and inert marker techniques. Samples were prepared by vacuum deposition of thin films of nickel and silicon, followed by thermal annealing to effect silicide growth. The radioactive tracer investigation of Ni2Si showed nickel to be the diffusing species during silicide growth. Sharply defined Ni2si* profiles of 100% radioactive concentration at the sample surface were - obtained. The results are compared with previous results in which the profiles were more spread out and of lower surface concentration. The radioactive tracer investigation of NiSi formation showed that nickel is also the diffusing species during second phase growth. The NiSi * layer was found to be of 100% concentration. Some spreading of the activity profile near the NiSi/NiSi* interface was observed. The results were consistent with previous 31Si tracer work on NiSi formation and also with the present Ni * 2Si results. The inert marker investigation used an ultra-thin (5-10 A) continuous layer of Mo or Ta to monitor atomic movement during silicide growth. The results confirmed nickel to be the diffusing species during the growth of both phases. These results are in excellent agreement with previous inert marker studies of nickel silicide growth.
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    Solid state diffusion in Pd₂Si
    (1986) Egan, John Mathew; Comrie, Craig M
    The atomic transport processes ocurring in the Pd/Si system have been investigated. The Pd₂Si system has been studied to try and establish the mechanism(s) of diffusion by which the growth of Pd₂Si proceeds under thermal annealing. Using a deposited Ti marker, the dominant moving species during Pd₂Si formation in the temperature range 250-400°C has been determined to be silicon. Palladium transport appears to occur during the initial stages of formation of Pd₂Si. Once several hundred angstrom of Pd₂Si has been formed, palladium transport seems to be replaced by silicon transport. Silicon tracer experiments, in conjunction with Si selfdiffusion measurements. indicate that silicon mobility is exceptionally high during the formation of Pd₂Si on Si substrate. During growth. the mobility of silicon is orders of magnitude higher than under equilibrium conditions. This is thought to suggest a vacancy mechanism of diffusion, and is expected that large numbers of vacancies are generated at the growth interface during silicide formation. Silicon self-diffusion in Pd₂Si has been investigated. The results indicate that grain-boundary diffusion could be operative under equilibrium conditions. Under the assumption that grain-boundary diffusion does occur during thermal annealing in the range 350-550°C, it is deduced that at all times the grain-boundary diffusivity is so much greater than the lattice diffusivity, that the grain-boundaries are effectively able to act as sources for the grains. The activation energy for lattice self-diffusion of silicon in Pd₂Si which has grown on Si<100> substrate, has been determined to be 0.8±0.3eV. This value is thought to support recent kinetic results which indicate that the activation energy for growth of Pd₂Si is in the region of 1eV.
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    A study of copper diffusion through Pd₂Si thin films
    (1997) Geduld, Dieter Rudi; Comrie, Craig M
    It is now generally recognized that unless an alternative for aluminium is found the resistivity of the metal interconnects will soon limit device performance. Copper, with its low resistivity and greater resistance to electromigration is one of the obvious substitutes. However, before aluminium can be replaced by copper, a careful study of the reactivity of copper with metal-silicides used in devices needs to be carried out. This study involves a dynamic RBS investigation of the reaction of copper with Pd₂Si films grown on Si<100> and Si substrates. It was found that copper diffused through the Pd₂Si layer and reacted with the single crystal silicon substrate at relatively low temperatures. The onset temperature observed for copper diffusion was found to differ for Pd2Si films grown on the two different substrate orientations, Si<100> and Si. Measurements of the activation energies for Cu-silicide growth on Pd₂Si/Si<100> and Pd₂Si/Si were also made.