The Structure of Tin Thin Films Evaporated onto a Clean NaCl Substrate

Tin films, approximately 100 Å and less in thickness, evaporated onto NaCl substrate cleaved in ultrahigh vacuum and held at 25°–100°C under various deposition rates, from 0.3 to 30 Å/sec, have been investigated by reflection electron diffraction and transmission electron microscopy. The films generally consisted of discontinuous island nuclei and their distribution, size and shape were markedly influenced by imperfections of the substrate surface and deposition rate as well as substrate temperature. These nuclei had tetragonal structure and showed preferential orientation: (100)Sn∥(001)NaCl; [010]Sn∥[100] or [010]NaCl. Well oriented and relatively large grains could be produced by an electric field: dc 100–200 V/cm, applied to the substrate during the evaporation. Effects of an electron-beam bombardment on the structure of films have been also investigated and correlated with deformation of tin crystals.