Bond Energy, Ionization, and the Conductivity Modulus of Vitreous Semiconductors as Functions of Composition

Abstract

A vitreous solid does not have a long range geometric order but it may have a particularly interesting long range structural chemical order. The energetics of short range order, defined by the covalent character of the chemical bonds between the atoms, stand out in the vitreous state. From a chemical point of view, the chalcogenide glasses in the germanium-arsenic-selenium system are worth considering further, as covalent heterobonds are expressed most clearly in this sytem. To a first approximation we can consider the value of the band gap, which is related to the intrinsic conductivity of glass, as a measure of the difference between the energy of the electron-pair and the single-electron chemical bonds between the respective atoms, or alternatively as the ionization energy of a covalent bond. It is clear, then, that the value of the band gap must be less than the value of the energy required to break the corresponding chemical bond.

R. L. Myuller, Izv. Akad. SSSR, ser. fiz., 28:1279 (1964).