Local structure of technologically modified g-GeS2: resonant Raman and absorption edge spectroscopy combined with ab initio calculations

Abstract

We have used resonant Raman and absorption edge spectroscopy together with first-principle calculations in order to study the structure of GeS2 glasses (g-GeS2). The glasses were prepared under different melt temperatures and cooling rates, which are shown to significantly influence the g-GeS2 structure at the nano-scale. The combined use of Raman spectroscopy and ab initio calculations reveals the origin of the molecular level electronic structure and its connection to the interesting technological features of the g-GeS2. Local structure within the glasses is discussed in terms of atomic GenSm clusters. The band gaps computed for these clusters and their correlation to the experimental band gaps and the possible formation of band tail states are also discussed.