In this project the PI wishes to capitalize on his invention of the technique of Photoinduced Auger Electron Spectroscopy (PAES) by extending it to incorporate three novel experimental aspects. Compared to conventional Auger Electron Spectroscopy (AES) the PAES method probes the top most atomic layers of materials non-destructively and selectively. The PAES spectra that are produced are also free from the large secondary electron background that complicates conventional Auger spectroscopy. The PAES method has proven to be a major advance in the filed of Auger spectroscopy and is now being introduced in many laboratories. In the proposed work the PI will not only continue the investigations already underway but also attack the problems of the growth and stability of ultra thin films of metals and semiconductors on semiconductor substrates, of the elemental composition of the top layer in model multi-component heterogeneous catalysts, and of surface segregation to the top layer in NiAl alloys. Major new applications of PAES will be directed to the studies of defects in semiconductors and to fundamental studies of positron annihilation with core electrons, with specific attention given to the identification of charged defects and vacancy impurity complexes in GaAs, InP, Si, and CdTe. Additionally, the PI proposes to use PAES-annihilation-gamma coincidence experiments to measure, for the first time, the Doppler broadened annihilation gamma spectra associated with an individual core level. The experimental facilities will be upgraded through the completion of a highly efficient time-of-flight PAES spectrometer and the development of highly efficient field assisted positron moderators. These, and other activities, will be carried out with graduate students and post doctoral research associates who will thereby receive training in an area of experimental physics that is of great importance to industrial technology in the 21st Century. %%% In this project the principal investigator will extend the application of his invention of a new technique for studying the properties of solid materials and ultra thin films deposited on them. This technique, called Photoinduced Auger Electron Spectroscopy, has major advantages over the conventionally used Auger Electron Spectroscopy and is now introduced in many laboratories in the USA as well as in other countries. The present proposal presents a rich and varied research program, including the extension of the technique through the construction of ancillary apparatus. Graduate students and post doctoral research associates will receive excellent training in an area of experimental physics that is of importance to the industrial technology of the 21st Century. ***
