U.S.-Japan Cooperative Research: Laser-Surface Interactionsat High Excitation Density

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This award will support a two-year cooperative research project in physics between Dr. Richard F. Haglund, Jr., Department of Physics and Astronomy, Vanderbilt University, and Dr. Noriaki Itoh, Department of Physics, Nagoya University, Japan. They will study laser-induced desorption (laser sputtering) in semiconductors and insulators, and especially the effect of high electronic excitation density on such desorption. The high density results from the intensity of the laser light and the strong absorption of it that takes place in the irradiated material, leading to a comparatively large concentration of excited valence-band electrons. The scientists hope to obtain a clearer picture of the ways in which the electronic energy delivered by laser photons to dielectric and semiconductor surfaces is absorbed, transformed, and ultimately dissipated through defect generation, bond-breaking, and desorption. The program is designed to take advantage of unique facilities, experience, and interests in the two laboratories: the initial studies will be carried out with visible and ultraviolet lasers on well-characterized compound-semiconductor surfaces in Japan; at Vanderbilt, alkali halides and alkaline-earth fluorides will be studied using both time-resolved optical desorption and photoelectron spectroscopies. Use of a free-electron laser due to become operational at Vanderbilt in 1990 is also planned in these experiments. The interaction of laser light with various materials has been a subject of great interest almost from the invention of the laser, for both technological and scientific reasons. The development of substrates and coatings for lasers inevitably involved such studies, for example. At the present time the operative physical mechanisms in many technological applications of laser-surface interactions, such as laser-assisted thin-film deposition and laser microlithography, are not well characterized. It is the aim of this collaborative research project to contribute to a fundamental understanding of these interactions.