Observations of crystal orientation effects in tin-telluride thin films

Abstract Tin-telluride thin films may be crystallographically oriented to certain preferred directions either during evaporation on to glass substrates or during subsequent anneals. X-ray diffraction measurements reveal the effects of ambient gas and ambient gas pressure, and annealing ambient. Either {110} or {111} planes show preferred orientation when helium is used as evaporant ambient, while {100} planes show preferred orientation in argon. Annealing in vacuum produces {111} orientation while annealing in tellurium vapor produces {110} orientation. Crystallite size measurements reveal preferences related to growth of larger crystallites of preferred crystal direction normal to substrate as compared to unpreferred crystallites during evaporations of films. Size measurements indicate regrowth of preferred crystallites larger in plane of film during annealing. Two mechanisms are suggested to explain orientation effects in evaporation; scattering of evaporant atoms by the ambient gas and adsorption/ occlusion of ambient gas into the film. The inclusion of tellurium in regrowth is suggested as an explanation of the different regrowth habits in vacuum and tellurium vapor.