In a closely correlated study, we have investigated phase transformations and grain growth phenomena together with measurements of electrical resistivity in the silicides of tungsten, molybdenum, and tantalum. In the case of WSi2, we find the tetragonal structure at all temperatures of anneal between 700 and 1100 °C. Furthermore, the activation energy, 0.65 eV, derived from grain growth measurements is close to the value, 0.66 eV, derived from the increase in electrical conductivity. In the case of MoSi2, we find a mixture of hexagonal and tetragonal phases after annealing at 700 °C and pure tetragonal phase at 800 °C and above. Once again the activation energies derived from grain growth and electrical conductivity measurements are very similar. TaSi2 gives anomalous results compared with the other two silicides. Electrical conductivity shows an asymptotic behavior with increasing anneal temperature. This is probably related to the fact that tetragonal TaO2 was found in the films.
Using two-step annealing of wafers containing mechanically induced back-surface damage, we have shown that the presence of stabilized damage regions controls the development of front-surface defect denudation zones and internal SiOx nucleation. Using data from transmission electron microscopy, secondary ion mass specrometry profiling, and secondary ion microscopy measurements we have demonstrated that little or no direct correlation exists between measured (front-surface) oxygen depletion widths and defect denudation zone widths. Primary anneals at temperatures <600 °C have also been shown to produce no significant or measurable depletion of oxygen at the front surface of wafers.
Growth of epitaxial (100) CdTe films on (100) GaAs substrates by molecular beam epitaxy is discussed. X-ray diffraction, UV reflectance, photoluminescence, and transmission electron microscopy techniques were employed to characterize the film specimens. The high structural perfection of the layers was evidenced by line dislocation densities of ≤104/cm2 at the free surface of films ≂6.6 μm thick and by measurable excitonic photoluminescence (∼1.504 eV) at room temperature. The CdTe epilayers were smooth and mirrorlike in appearance.
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