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

该奖项将支持范德比尔特大学物理与天文系的Richard F. Haglund， Jr博士和日本名古屋大学物理系的Noriaki Itoh博士之间为期两年的物理学合作研究项目。他们将研究半导体和绝缘体中的激光诱导解吸（激光溅射），特别是高电子激发密度对这种解吸的影响。这种高密度是由于激光的强度和被照射材料对激光的强烈吸收，导致被激发的价带电子相对集中。科学家们希望能更清楚地了解激光光子传递到电介质和半导体表面的电子能量是如何被吸收、转化，并最终通过缺陷产生、键断裂和解吸而消散的。该项目旨在利用这两个实验室独特的设施、经验和兴趣：最初的研究将在日本用可见光和紫外线激光在表征良好的化合物半导体表面上进行；在范德比尔特，碱卤化物和碱土氟化物将使用时间分辨光学解吸和光电子能谱进行研究。将于1990年在范德比尔特大学投入使用的自由电子激光器也计划在这些实验中使用。由于技术和科学的原因，激光与各种材料的相互作用几乎从激光发明以来就一直是一个引起极大兴趣的主题。例如，激光衬底和涂层的发展不可避免地涉及到这类研究。目前，许多激光与表面相互作用的技术应用，如激光辅助薄膜沉积和激光微光刻，都没有很好地表征其物理机制。这个合作研究项目的目的是促进对这些相互作用的基本理解。

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.