Ab initio studies of the gas adsorption on the surface CdSe1-xSx ultra-thin films

In this study, we report for the first time the results of ab initio calculations of the electron band energy structure and optical properties for thin films of solid-state solution CdSe1-xSx (x = 0, 0.25, 0.50, 0.75 and 1.00) with the interaction of their surface with H-2 and NO2 molecules. It is practically important concerning the problem of developing new gas sensors and for the photocatalytic hydrogen (H-2) evolution. Concentration dependences of the energy gaps, the position of an energy level of the valence band, and the conduction band are studied. Interaction of the thin films with H-2 creates a tendency to decrease the band gap and transform its concentration dependence to a quasi-linear one. The concentration dependences of optical properties are mainly studied on the example of refractive index at the light wavelength 500 nm. Moreover, we elucidate the influence of adsorption of the H-2 and NO2 gas occurring on the surface of CdSe1-xSx thin films on their optical functions.