Effect of Bi Incorporation on the Optical Electrical and Thermal Properties of a Se Te and a Ge Te Glassy Alloys

Abstract

This thesis work is concerned with the effect of Bi incorporation on the optical, electrical and thermal properties of a-Se-Te and a-Ge-Te chalcogenide (ChG) glassy alloys. Glassy alloys and their thin films prepared and studied are: newlineI. Se85-xTe15Bix (x = 0, 1, 2, 3, 4, 5) newlineII. Ge20Te80-xBix (x = 0, 1.5, 2.5, 5.0) newlineMelt quenching technique has been used for the growth of glassy alloys. Thin films of prepared samples were deposited using thermal evaporation technique. X-ray diffraction technique has been used to know the nature (amorphous or crystalline) of bulk and deposited films. The optical properties have been estimated by analyzing the transmission and reflection spectra obtained from ultraviolet-visible-near infrared spectrometer. Swanepoel s method has been used to determine refractive index and extinction coefficient. Optical band gap has been calculated using Tauc extrapolation. The various electrical measurements on the thin films including both the dark and photoconductivity measurements at different temperatures were carried out in a metallic sample holder under a vacuum ~ 10-3 mbar throughout the measurements. In order to measure the thermal properties of a-Se-Te-Bi Differential Scanning Calorimetric technique (DSC) has been used whereas in case of a-Ge-Te-Bi system Differential Thermal Analysis (DTA) method has been employed. Some of the physical parameters have also been estimated for both of these series. newline