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 Ge _n S _m 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.

Acknowledgements

We are grateful to N. Mateleshko for many helpful discussions and M. Veresh (Hungarian Institute for Solid State Physics and Optics) for his assistance in part of the experiments. R.H. would like to thank the Swedish Institute for scholarship support. The present work was partially supported by the ministry of education and science of Ukraine (Grant Nos. M/467-2003 and 29/48-2001). The main part of the calculations was performed at the Condensed Matter Physics Group (CTH) Linux cluster.