ELECTRON-MICROSCOPIC STUDIES OF VACUUM-EVAPORATED (PB1-XSNX)1-YTEY THIN-FILMS

Thin films of (Pb1-xSnx)1-yTey have been deposited by vacuum evaporati on onto glass, mica, CaF2 and NaCl substrates heated to various temper atures 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 substr ate 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 increasing T(sub), grains ten d to form clusters through mobility coalescence. Needle-shaped grains are formed when the deposition rate exceeds a certain critical value. Formation of needle-like grains has been attributed to the excess Te a toms possessing trigonal structure so that such grains can be observed only in p-type PbSnTe films.