Metastable States in Amorphous Chalcogenide Semiconductors

This book presents experimental results on the structural and electronic metastable states in Se-rich chalcogenides. Coverage includes states in the mobility gap, structural transformation, photocrystallization, and many potential related applications. This book addresses an interesting and technologically important class of materials, the amorphous chalcogenide semiconductors. Experimental results on the structural and electronic metastable states in Se-rich chalcogenides are presented. Special attention is paid to the states in the mobility gap and their sensitivity to various factors such as irradiation, annealing and composition. Photoinduced changes of structure and physical properties are also considered and structural transformation at photocrystallization is studied in detail. Finally, the authors discuss potential applications of the observed effects in xerography, digital radiography and for optical data storage. 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.