The precise role of UV exposure time in controlling the orbital transition energies, optical and electrical parameters of thermally vacuum evaporated Se50Te50 thin film

Abstract

Abstract The scenarios for this work have been summarized in the preparation of the Se50Te50 thin film -(~500 nm)- by thermal evaporation method, then using a mercury lamp with a 150 W/cm2 as a source of ultraviolet radiation. The irradiation process has been carried out in the open air for the Se50Te50 thin film without irradiation and in the UV-treated period between 0.5 and 2.5 h. A thorough study has been carried out which ultimately has been confirmed from it that the irradiation time plays the role of controlling the optical and electrical properties. The energy band type corresponding to the orbital transitions has been determined, and the energies of the orbital transition has been calculated in the Tauc region, HOMO/LUMO gap, and charge transfer gap. In addition to, calculating the exciton and Urbach energies. It has been found that these energies decrease with increasing UV exposure time, except for Urbach's energies, which behave differently. The role of the UV exposure time in controlling many optical constants, dispersion, and dielectric parameters was investigated. Thin-film quality coefficient, the surface resistance, and thermal emission, in addition to the angle of refraction as a function of wavelength, have been determined. As well, the spectral distribution of the molar parameters has been discussed. Finally, the DC electrical conductivity, the activation energy in the extended and hopping state regions, and Mott's parameters have been computed.