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CVD Growth of Tin Selenide Thin Films for Optoelectronic Applications

Tin Selenide (SnSe) thin films were grown onto glass and alumina substrates by Chemical Vapor Deposition (CVD) method. The structural, micro-structural and morphological characterizations of the as grown thin films were investigated using XRD, SEM and Raman spectroscopy which reveals that the films on glass are phase pure oriented SnSe while those on Alumina are polycrystalline SnSe with SnSe2 impurity phase. The optical properties of the films grown onto glass substrate were studied by UV-vis spectroscopy. The optical band gap calculated is 1 to 1.3 eV for indirect and direct transition in film deposited on glass substrates. The Arrhenius plots of the two films show very different thermal activations i.e. 0.088 eV for tin vacancy acceptor level close to valance band maxima in pure SnSe and 0.44 eV for mid gap selenium vacancies of SnSe2. Photoresponse was observed by illuminating the sample (Glass and alumina Substrate) using white and UV light (400 nm) for a fixed time pulses. The deposited onto Alumina substrate were found to show better photoresponse due to SnSe/SnSe2 p-n heterojunctions.