Electronic Structures of Amorphous Solids

Abstract

The nature and behaviour of electron states in amorphous solids are reviewed. The usefulness of the density of states as a description of electron states when the electron wavevector is ill-defined (in the absence of translational symmetry) is discussed. The origin of the valence and conduction band states of representative amorphous semiconductors (Si and Se) is explained, and the reasons why a band gap should occur in the amorphous state are discussed. The concept of electron localization is introduced, and this is used to describe the characteristics of electron states in the gap of amorphous semiconductors. Finally, two experimental techniques (photoemission and optical absorption) are described which can be used to provide information on the electronic states in amorphous solids.