Annealing effect for SnS thin films prepared by high-vacuum evaporation

Thin films of SnS are deposited onto molybdenum-coated soda lime glass substrates using the high-vacuum evaporation technique at a substrate temperature of 300 degrees C. The as-deposited SnS layers are then annealed in three different media: (1) H2S, (2) argon, and (3) vacuum, for different periods and temperatures to study the changes in the microstructural properties of the layers and to prepare single-phase SnS photoabsorber films. It is found that annealing the layers in H2S at 400 degrees C changes the stoichiometry of the as-deposited SnS films and leads to the formation of a dominant SnS2 phase. Annealing in an argon atmosphere for 1 h, however, causes no deviations in the composition of the SnS films, though the surface morphology of the annealed SnS layers changes significantly as a result of a 2 h annealing process. The crystalline structure, surface morphology, and photosensitivity of the as-deposited SnS films improves significantly as the result of annealing in vacuum, and the vacuum-annealed films are found to exhibit promising properties for fabricating complete solar cells based on these single-phase SnS photoabsorber layers. (C) 2014 American Vacuum Society.