High Quantum Efficiency Spin-polarized Photocathodes

154 High Quantum Efficiency Spin-polarized Photocathodes--Spire Corporation, One Patriots Park, Bedford, MA 01730-2343; (617) 275-6000 Mr. Stanley M. Vernon, Principal Investigator Mr. Richard S. Gregorio, Business Official DOE Grant No. DE-FG02-97ER82480 Amount: $74,991 Electron accelerators are a major tool used in high-energy and nuclear-physics research. Efficiency of accelerator experiments is currently limited by the electron flux that can be generated by the electron source, a so-called ¿photocathode¿. Current technology, using gallium arsenide (GaAs), a common semiconductor with a mature thin-film deposition technology, unfortunately leads to low efficiency (low electron flux). This project will develop the technology for reliably producing more efficient photocathodes by developing a different class of semiconductors, (chalcopyrites) leading to a much higher electron-generation efficiency. Deposition of thin-film chalcopyrite layers will be the major challenge; films will be deposited by a process called metalorganic chemical vapor deposition (MOCVD). Phase I will focus on choosing the chalcopyrite with the best trade-off in terms of high efficiency versus ease of deposition, developing MOCVD growth of this material, and evaluating films through photocathode characterization at the Department of Energy¿s Jefferson Laboratory. Challenges for Phase II include optimizing p-type chalcopyrite growth, control of carrier concentration, and photocathode fabrication in a new material system. Commercial Applications and Other Benefits as described by the awardee: Success in this project would lead to a technology for producing high-efficiency photocathodes, useful in all electron-collider facilities. Other possible applications include polarized-electron sources for study of surfaces of magnetic materials or in biophysical research to study surface magnetic properties of electrically active neurological cells.