We are focusing on studying Bi2S3 topological insulator materials. The topological insulators are recently discovered class of Dirac materials with host symmetry protected conducting surface states. The conduction on the surface of a 3D topological insulator and along the edges of a 2D topological insulator is robust against back-scattering and offers the possibility of dissipation less electronic transport. The electrons on the surface (or edges) of topological insulators have a Dirac cone like band structure with a linear energy versus momentum dispersion. Strong spin orbit coupling, which is a primary ingredient in creating such an unusual surface dispersion, also lends a unique spin texture to the surface electrons. The spin of these surface carriers in locked to its momentum in that electrons moving in opposite directions have opposite spin. Moreover, the possibility of observing exotic physical objects like Majorana fermions and magnetic monopoles by interfacing 3D topological insulators with various other condensed matter systems like ferromagnet and superconductor has made this area of research very exciting. From an experimental point of view, over the past few years, materials belonging to the Bi2Se3(S3) (bismuth based chalcogenides) family have come to be regarded as suitable candidates for observing 3D topological insulators. We are doing this work in collaboration with Prof. P.S. Anil Kumar’s lab.
Our group focuses on the study of chalcogenide based solar materials like Copper zinc tin sulfide (CZTS). It is a quaternary semiconducting compound which has received increasing interest since the late 2000s for applications in solar cells. The CZTS offers favorable optical and electronic properties similar to CIGS (copper indium gallium selenide) making it well suited for use as a thin-film solar cell absorber layer. It includes earth abundant materials like Sn, Zn and less toxic S. In additions CZTS exhibits excellent materials properties such as direct band gap of 1.4 to 1.5 eV and large absorption coefficient of 104 cm -1 in visible spectrum range. Recently, the conversion efficiency of CZTS solar cell was dramatically increased.
Chalcogenide glasses are playing an important role in device applications. They exhibit electrical and optical properties, which make them useful for several potential applications in Xerography and Photovoltaic devices. The threshold and memory switching behavior and the infrared transmission of many of these glasses make the materials well suited for use in memory devices and in fiber optics system. The chalcogenide multilayers are also attractive because of their prominent photo induced effects. Based on these effects one can tune the optical band gap of the materials. In our group, we mainly concentrate on preparation of chalcogenide glassy bulk materials as well as multilayers thin film and study the structural and optical properties of these materials as well as to carry out the photo induced effects on these glassy systems.