9505618 Lapeyre This project will use synchrotron radiation photoemission spectroscopy and other electron spectroscopies to study the structure and electronic properties of overlayers on semiconductor surfaces. Emphasis will be given to the performance of photoelectron diffraction experiments where scanned energy spectra can be inverted to obtain three dimensional images of the photoemitting atom and its near neighbors. The inversion is a Fourier-like transform based on the holographic principle and does not require any external input to obtain an image. The technique has been demonstrated on various systems including Al, Ga, As and Se on Si surfaces. Of particular interest for future investigations are structural changes that influence the nature of growth--both homo- and hetero-epitaxy--at semiconductor surfaces and the electronic properties of surfaces. Photoemission holography will be applied to structure determination of systems composed of various adsorbates on Si, GaAs, and ZnSe. Two new applications of the holographic technique will be developed: a) a single adsorbate on a compound semiconductor substrate, and b)multiple adsorbates on an elemental semiconductor substrate. %%% A new atomic-level materials characterization technique, photoemisson holography, is being developed and applied to basic synthesis and processing research studies of materials with strong technological relevance to electronics and optoelectronics. An important feature of the program is the training of students in a fundamentally and technologically significant area of materials research. ***
