9403806 Taylor Technical abstract: Metal chalcogenide glasses are a model system that provides a link between the tetrahedrally-coordinated amorphous materials, such as hydrogenated amorphous silicon and the traditional chalcogenide glasses, such as selenium or arsenic selenide. The research will answer questions concerning the structure, defects and doping mechanisms in metal chalcogenides glasses where both the metal and chalcogenide atoms can be tetrahedrally coordinated. Important questions concern the microscopic origins of optically-induced paramagnetidm, of photodarkening, and potential doping mechanisms. The specific objectives are (1) to understand the details of the local structural order in metal-containing chalcogenide glasses, (2) to study the intrinsic defects in metal chalcogenide glasses as the structure is changed from low to high average coordination number, (3) to understand the p-type doping mechanism in the Cu-As-Se(S) systems, and (4) to further the understanding of the photodarkening process and the defects that contribute to photodarkening, especially those defects that involve optical anisotropies. Non-technical abstract: In order for semiconductors to be useful as electronic devices on must be able to change their electrical properties dramatically by a process called "doping". In most semiconductors where the atoms are not well ordered (amorphous semiconductors) it has generally been assumed that doping is not possible. We have demonstrated the feasibility of inefficient doping in a class of amorphous semiconductors containing sulfur. Selenium or tellurium and are investigating ways of improving the doping and expanding our understanding of the process. Amorphous semiconductors also have the property that they are metastable and that their electronic and optical characteristics can change. These metastabilities are sometimes deleterious to device performance, as in the degradation of thin-film transistors with time, but so metimes they are useful, as in the use for optically- induced index changes in inorganic photoresists. These metastabilities will be studied to understand the basic microscopic mechanism essential for the design of useful devices. ***
