An Optical Study of Chalcogenide Glasses Using UV Vis NIR Spectroscopy

Abstract

The work reported in this thesis is concerned with the study of optical properties of Ge-Se-Te system and the effect of metal impurities (Bi, Cd, Pb and Sn) on the optical properties of As-Se-Ge system. Various bulk samples and their thin films prepared and studied are: newline1.Ge10Se90-xTex ; x = 0, 10, 20, 30, 40, 50. newline2.(As2Se3)90Ge10 newline3.[(As2Se3)90Ge10]95M5 ; M = Bi, Cd, Pb and Sn. newlineBulk samples were prepared by melt quench technique. Thin films of prepared samples were deposited using thermal evaporation technique at base pressure of ~10-4 Pa. X-ray diffraction technique has been used to know the nature (amorphous or crystalline) of bulk and deposited films. Far-infrared transmission spectra have been obtained from FT-IR spectrophotometer to study the bonding arrangements in Ge-Se-Te system. The optical properties (refractive index and extinction coefficient) have been estimated by analyzing the transmission spectra (200 2400 nm) 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 determined using Tauc extrapolation. The effect of deposition parameters (type of substrates, thickness and substrate temperature) has been examined on the refractive index and optical energy gap of Ge-Se-Te thin films. Physical properties (coordination number, density, compactness, theoretical energy gap, cohesive energy and heat of atomization) of Ge-Se-Te glassy alloys have also been determined. The effect of metal impurities (Bi, Cd, Pb and Sn) on the optical properties has been studied for As-Se-Ge thin films. newline