An X-ray fourier line shape analysis of hexagonal tellurium films III: Vacuum evaporated onto air-cleaved mica substrates at low temperature (133 K)

Abstract

As a continuation of a series of studies of hexagonal tellurium films deposited onto glass at room temperature and low temperature (133 K), investigations were carried out on the growth structure of tellurium films 331–800 nm thick (for normal vapour incidence) and 260–1129 nm thick (for oblique vapour incidence) deposited by vacuum evaporation at various rates of deposition onto air-cleaved mica substrates at a temperature of 133 K. Since mica is a crystalline substrate it was used to study its influence on the growth structures and preferred orientation. Considering the cases of normal and oblique vapour incidence for both high and low rates of deposition, a small domain or crystalline size effect (about 115–160 Å), appreciable microstrains (2.2–5.0)×10 -3 in the domains and a near-isotropy in the size and strain parameters were observed from a detailed Fourier analysis of X-ray diffraction profiles. The results obtained from the analysis of fault-affected reflections ( H - K = 3 N±1, L 0 odd or even) show that the intrinsic stacking faults (probability α) are totally absent and the presence of growth stacking faults (probability β) is also negligible. The dislocation density ϱ is about 10 11 cm -2 and a c axis texture is found to develop in the films. The average residual internal stresses σ and lattice parameter changes Δ a and Δ c, obtained from line shift analysis, are small. From a comparison of the results obtained for the different cases it appears that the changes in the angle of deposition or the rate of deposition as well as the nature of the substrate (mica) do not markedly affect the growth structures and orientation of the films deposited at this lower temperature.