In6Se7 thin films by heating thermally evaporated indium and chemical bath deposited selenium multilayers

Indium selenide (In6Se7) thin films were prepared via selenization of thermally evaporated indium thin films by dipping in sodium selenosulphate solution followed by annealing in nitrogen atmosphere. First, indium was thermally evaporated on glass substrate. Then, the indium coated glass substrates were dipped in a solution containing 80 ml 0.125 M sodium selenosulphate and 1.5 ml dilute acetic acid (25%) for 5 min. Glass/In–Se layers were annealed at 200–400 °C in nitrogen atmosphere (0.1 Torr) for 30 min. X-ray diffraction studies showed the formation of monoclinic In6Se7. Morphology of the thin films formed at different conditions was analyzed using Scanning electron microscopy. The elemental analysis was done using Energy dispersive X-ray detection. Electrical conductivity under dark and illumination conditions was evaluated. Optical band gap was computed using transmittance and reflectance spectra. The band gap value was in the range 1.8–2.6 eV corresponding to a direct allowed transition. We studied the effect of indium layer thickness and selenium deposition time on the structure, electrical and optical properties of In6Se7 thin films.