Growth and characterization of Cu2SnSe3 thin films

Thin films of Cu2SnSe3, a potential candidate for acousto-optic device applications in IR region were prepared by co-evaporation onto glass substrates. Powder X-ray diffraction (XRD) pattern revealed that the films were polycrystalline in nature with sphalerite structure. The lattice parameter was found to be a = 0.573 nm. Grazing incidence X-ray diffraction (GIXRD) studies indicated that the surface layers contain Cu2SnSe4 as the secondary phase. Average grain size obtained from scanning electron micrograph was found to be 0.6 μm. Optical absorption studies revealed two direct-allowed transitions, one corresponding to the transition from the acceptor level to the bottom of the conduction band (0.74 eV) and the other corresponding to the transition from the spin-orbit splitting level to the conduction band minimum (1.12 eV). The films were found to be p-type with a carrier concentration of 1.85 × 1020 cm−3 and Hall mobility of 1.79 cm2 V−1 s−1. Temperature dependence of electrical conductivity studies in the range 123–373 K indicated three acceptor states with activation energies of 60, 15 and 5 meV.