Defects and the Photodarkening Process in the Chalcogenide Glasses

摘要

In the chalcogenide glasses the primary defects are thought to involve under- and over- coordinated chalcogen atoms which are diamagnetic under quasiequilibrium conditions because of the presence of a strong electron-lattice interaction. These defects can be optically, or in some cases thermally, excited into metastable paramagnetic configurations which are well described as chalcogen dangling bonds. Alloying the chalcogenide elements with group V or group IV atoms produces additional diamagnetic defects which in their excited paramagnetic configurations also appear to be well described as dangling bonds. Some of these defects may play a role in the photodarkening (PD) process which is a metastable shift of the absorption edge to lower energies after irradiation with light of energy greater than or equal to that of the band gap. The PD process requires the presence of a non-bonding p like valence band. The microscopic description of the PD process may involve the creation of defects or the tunneling of chalcogen atoms. Keywords: Glasses, Defects, Electron lattice interaction, Paramagnetism.