Investigations of thermal, optical and electrical properties of Se85In15−xBix glasses and thin films

Abstract

In our present research work, we have investigated the different thermal, optical and electrical properties of Se85In15−xBix alloys in bulk and thin film form. Differential Scanning Calorimeter (DSC) was operated at different heating rates of 5, 10, 15, 20 and 25 K min−1. The melting temperature (Tm), peak crystallization (Tp), on-set crystallization (Tc) and glass transition (Tg) temperature were evaluated from DSC curves. The value of Tg, Tc and Tp was found to increase with the heating rate. Depending on these parameters, we have estimated the different thermal stability parameters. The activation energy of crystallization (ΔEc) and activation energy of glass transition (ΔEg) was evaluated by different methods and found to be in good agreement with each other. Thermal evaporation technique has been used for preparation of Se85In15−xBix thin films of thickness 500 nm. The X-Ray Diffraction studies confirm amorphous texture of as-prepared thin films. The morphology of surface was examined by Field Emission Scanning Electron Microscope. It has been observed from FESEM studies that by increasing the Bi content the cluster of particles increase, which indicate good alloying of Bi in Se85In15−xBix thin films. Different optical parameters have been calculated by optical absorption measurements of Se85In15−xBix thin films in wavelength range 400–1100 nm. With the increase in incident photon energy, absorption coefficient (α) and extinction coefficient (k) are found to be increase. The optical absorption obeys the indirect transition rule and with increasing Bi concentration the optical band gap decreases. We have also evaluated the steepness parameter (σ) and Urbach energy (Et) values from optical studies. In electrical studies, we have performed the dc-conductivity measurement at different temperature from 298 to 403 K. From these measurements, we have calculated the different electrical parameters like activation energy (ΔEc), pre-exponential factor, free carrier concentration density, mobility, etc.