Physical properties of InxSey and CuInSe2 thin films with potential application in radiation detectors

A study of In x Se y and CuInSe 2 thin films processed by the thermal co-evaporation technique by evaluating its physical properties is carried out. Both In x Se y as well as CuInSe 2 thin films were synthesized by multi-source thermal co-evaporation technique, using Knudsen-type effusion cells. The optical, structural, electrical, and morphological properties of each film were analyzed in order to determine the feasibility at the formation of a p-CuInSe 2 /n-In x Se y heterojunction. In x Se y films exhibited bandgap values in the range of 2.4–2.7 eV which was determined by UV–vis spectroscopic analysis. Vibrational modes associated to In 2 Se 3 as well as Se are presented in the In x Se y films according to Raman studies. The irregular morphology of the grains on the In x Se y surface, with an average size of 380 nm are related to both In 2 Se 3 and Se materials according to Raman spectroscopy and Scanning Electron Microscopy analysis. The In x Se y thin films showed resistivity vales around 10 –3 Ω·cm. The Hackee´s figure of Merit (FOM H ) analysis supported the physical assumption that In x Se y thin films are feasible to be used as window layer in a photovoltaic device because of the high values of FOM H obtained for samples processed at 300 °C. On the other hand, an influence on the morphology of the CuInSe 2 films was observed when the films were synthetized at different substrate temperature. Uniform CuInSe 2 films with agglomerated cauliflower-like grains with an average size of 1.8 μ m were observed by SEM. The presence of binary phases within the CuInSe 2 compound were detected through Raman and x-ray characterization. Average crystallite size of 61 nm and microstrain around 2.5 × 10 –3 were estimated for the CuInSe 2 films through x-ray analysis. According to the physical properties analyzed the In x Se y /CuInSe 2 semiconductor bilayer can be a suitable candidate for application in photovoltaic devices as well as charged particle detector.