Intrinsic defect states and electron spin resonance in the Ge-S bulk glasses

Abstract

A review of electron paramagnetic resonance (ESR) of bulk glassy Ge-S system is presented. The long-range periodicity in amorphous materials and glasses is disturbed by the fluctuations of bond angles, bond lengths and by composition as well. In a limit case an increase of the bond lengths can break chemical bonds between atoms of glass and so-called dangling bonds are formed. These are singly occupied and thus paramagnetic if stabilized by lowering of Hubbard´s energy. The dangling bonds in chalcogenide glasses and their relation to the ESR spectra are still questionable. Dangling bonds however can interact with nearest atoms of glass and create another type of multiatomic defect centers which are still paramagnetic. This review can also help to solve the problem why in the whole class of chalcogenide glasses the so-called dark ESR signal is found in Ge-S glasses only.