This monographdeals with metastable states in amorphoussemiconductors- ma- rials which lack long-range periodicity in the atoms' positions, which are in th- modynamic nonequilibrium and which, in addition, have several metastable states. Thesestates giverise tovariouspropertiesandeffects- namelya widerangeofp- toinduced changes and high photosensitivity and X-ray sensitivity - that are unique among solid-state semiconductors.Historically, amorphousselenium and seleni- based materials have played an important role in physics and technology, and they continue to do so. In these materials there exist inherent intermediate (metastable) states, structural and electronic in origin, which lead to interesting properties and effects different from those of their crystalline counterparts. In this volume, the metastable states and related effects are investigated in depth against the background of a detailed consideration of local atomic and electronic structure, and taking into account a wide range of light-induced effects.
Although the rst publications on amorphous semiconductors date back to the early 1970s, studies of metastable states in these materials had not been analyzed systematically up to now, which led to erroneous ideas, even among specialists. In the present book, experimental investigations of metastable states are reported in detail for elemental selenium and selenium-based materials.