Characterisation of SnSe thin films fabricated by chemical molecular beam deposition for use in thin film solar cells

SnSe thin films were fabricated the first time by chemical molecular beam deposition (CMBD) in atmospheric pressure hydrogen flow using polycrystalline tin selenium (SnSe) precursors. The morphological and electrical properties of the films were studied as a function of the precursor's composition and the substrate temperature. Experimental data indicate that in the resulting thin films Se enrichment takes place at low substrate temperatures, despite the different compositions of the SnSe precursor during the synthesis. In this case, the grain sizes of the films vary in the range of (8-20) µm, depending on the substrate temperature. In addition, X-ray diffraction analysis of the samples shows that the films have an orthorhombic crystalline structure. The electrical conductivity of films measured by van der Pauw method varies between 6 and 90 (Ωxcm)-1. The optical measurements on selected SnSe thin films illustrate that the samples have an optical bandgap of (1.1-1.2) eV and the absorption coefficient of 10^5 cm-1, which is suitable for thin film solar cells.