Metal-non-metal transition in silver chalcogenides

Abstract

Abstract The paper reviews the crystallographic, optical, magnetic and transport properties of silver chalcogenides Ag2S and Ag2Se. In the low temperature β-phases, the influence of stoichiometry on the respective magnitude of ionic and electronic conductivities is important. In the disordered high-temperature α-phases, the characteristic feature is the statistic distribution of lattice silver ions. This situation is analysed according to the theory established by Mott (e.g. 1974, and Mott and Davis 1971) for amorphous semiconductors. Owing to the disorder, tails appear both in valence and conduction band, and in α-Ag2Se, the bands overlap.