RUI: Radiation selectivity of photo-induced structural transformations in covalently bonded glassy thin films

Austin Peay State University, Clarksville TN

Investigators

Abstract

NON-TECHNICAL DESCRIPTION: Chalcogenide glass thin films, due to their multifunctionality and unique properties, are remarkably promising materials for emerging applications in infrared photonics, non-linear optics, all-optical computing, micro(nano)-lithography, and phase-change memory devices. These materials are exceptional because of their multilevel sensitivity to exposure by light or particles (electrons, neutrons, ions); this sensitivity depends on the intensity and energy of the radiation source. Light treatment can also be used to accelerate structural relaxation in amorphous films, stabilizing their properties for further applications. However, to control the photo-(or light-)induced effects and predict behavior of the exposed material, the mechanisms of photostructural transformation on the surface and inside of the films at different light energies and intensities needs to be better understood. The goal of this project is to develop, using advanced experimental methods, a new level of understanding of the photostructural transformations and establish an efficient way to stabilize the structural relaxation of chalcogenide glass thin films prepared by different methods. Undergraduate research is an essential part of the project, providing students access to the advanced experimental facilities and inspiring them to consider a career in science or engineering. TECHNICAL DETAILS: As-S(Se) (pyramidal) and Ge-S(Se) (tetrahedral) binary chalcogenide glass thin films, within a wide compositional domain, thermally deposited in vacuum as well as spin-coated from solution are being studied. The thermally-deposited films are known for their high photosensitivity and a large concentration of homopolar bonds, even for stoichiometric compositions. While, the spin-coated films are relatively photo-stable with structure close to the bulk analogue. The project's planned outcome is an atomistic picture of the structural response to photoexposure and its dependence on photon energy and fluence for pyramidal and tetrahedral chalcogenide glass thin films obtained with the two different methods. The mechanisms of photostructural transformations are studied with Raman microscopy, high-resolution X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, optical spectroscopy, X-ray absorption and neutron scattering methods. The project's results have the potential to stimulate major progress in application of chalcogenide glass thin films in emerging fields such as photonics, memory devices, and micro/nanolithography. As well, one of the main objectives of the project is the development of a nationally recognizable undergraduate research training program in experimental and computational glass science.