Proximity co-evaporation growth of SnSe thin films for high-responsivity photodetectors

In this work, tin selenide (SnSe) thin films were successfully synthesized using a cost-effective proximity co-evaporation method within a chemical vapor deposition (CVD) system. The process involved a thermally evaporated Sn thin film and selenium powder as precursors, arranged in a source-substrate-face-to-face configuration to enable uniform and self-limiting lateral growth under an inert atmosphere. X-ray diffraction (XRD) confirmed the formation of orthorhombic SnSe with high crystallinity and phase purity. Field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS) revealed a uniform grain morphology and near-stoichiometric composition, while X-ray photoelectron spectroscopy (XPS) confirmed the presence of Sn²⁺ and Se^2- oxidation states. Optical studies revealed a band gap of ∼1.15 eV, aligning well with the ideal range for optoelectronic applications. Electrical measurements demonstrated ohmic contact behavior, and photoresponse analysis under white LED illumination exhibited a significant enhancement in photocurrent, with a responsivity of 29.9 A W^-1, detectivity of 3.8 × 10¹¹ Jones, and quantum efficiency of 67.45%. These results show that the fabricated SnSe thin films could be suitable candidates for high-performance photodetectors and optoelectronic devices.