Localized Electronic States in Amorphous Semiconductors

University Of Utah, Salt Lake City UT

Investigators

Abstract

The electronic, optical, and structural properties of amorphous, chalcogenide (Group VI) semiconductors are of increased interest because of their use in reprogrammable optical storage devices (phase change memories), optical fibers, and other electro-optical devices. Many of these devices are plagued by optically induced changes in the local structural order, which are ubiquitous in these semiconductors. Optical and magnetic resonance experiments and tight-binding calculations are directed at understanding both the local order and the metastable, optically induced changes. This understanding, which will apply to a wide range of amorphous semiconductors, has the potnetial to greatly improve the performance of many devices. Graduate students are trained in the most advanced optical and magnetic resonance techniques. Special emphasis is placed on the active recruitment of women at both the undergraduate and graduate levels. An outreach effort with a predominantly undergraduate institution has attracted several undergraduate women. Summer employment is offered to high school students identified as especially talented and motivated. Undergraduate students are encouraged to present talks at scientific meetings. In response to recent developments within the scientific community, a new course on Scientific Ethics is being developed at the advanced undergraduate/graduate level. In the standard semiconducting materials, such as those used for computer applications, the individual atoms are arranged in space like cubes stacked in a box. If this regular geometry does not exist the semiconductors are called "amorphous". The properties of a particular class of amorphous semiconductors, namely those that contain atoms from Group VI of the periodic table, are of special interest because of their use in optical fibers. These momories and fibers are plagued by deleterious changes in performance that are induced by light. The research is aimed at understanding these changes and ultimately at curtailing these deleterious effects. In the course of performing the experiments undergraduate and graduate students are trained in the most advanced optical and magnetic resonance techniques, whose medical analogs include laser eye surgery (Lasik) and magnetic resonance imaging (MRI). Special emphasis is placed on the active recruitment of women. Outreach efforts include close collaboration with local colleges and high schools. The scientific community has recently witnessed prominent breaches in ethical standards. In response to these developments a new course on Scientific Ethics is being offered at the University of Utah.