Abstract
Thin films of (Pb1 −x Sn x )1 −y Te y have been deposited by vacuum evaporation onto glass, mica, CaF2 and NaCl substrates heated to various temperatures at low deposition rates. Transmission HEED, TEM and SEM studies have been carried out for as-grown films. HEED photographs show that (i) the degree of crystallinity of the films improves at higher substrate temperatures and (ii) the crystallites have smaller dimensions on CaF2 than on NaCl, mica and even glass, under identical conditions of deposition. SEM studies reveal that with increasingT sub, grains tend to form clusters through mobility coalescence. Needleshaped grains are formed when the deposition rate exceeds a certain critical value. Formation of needle-like grains has been attributed to the excess Te atoms possessing trigonal structure so that such grains can be observed only inp-type PbSnTe films.
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