Surface Structure and Chemistry of the Boron-Rich Solids

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9421037 Trenary The metal borides are intriguing materials that are extremely hard, chemically inert, and have very high melting points. Many of these solids have unique properties making them useful in various applications. For example, lanthanum boride and cerium boride are widely used as electrmn emitting cathodes in a variety of electron optical devices and are far superior to tungsten and other refractory metals for this purpose. High-quality single crystals of yttrium boride are being developed for use as monochromators of 1-2 keV synchrotron radiation. Because of the importance of surface structure and surface properties in thermionic emission, the rare-earth hexaborides have been the subject of many fundamental surface science studies. Yet many of the most important properties have not been investigated. One of the most important questions in the use of hexaborides as cathodes concerns their interaction with the background gases present in all vacuum chambers. In this work, reflection absorption infrared spectroscopy will be used to characterize the adsorption and decomposition of simple background gases on the lanthanum boride and cerium boride surfaces. Scanning tunneling microscopy also will be used for structural studies of the number of technologically important metal boride surfaces. %%% Little is known about the surface chemistry of boron-rich solids. These solids constitute a wide and varied class of materials. They are of high interest to the electronics industry as cathodes for electron beam lithography, and electron emitting cathode in a variety of electron devices. Furthermore, transition metal diborides as thin films in metal surfaces are important application areas requiring ultra-hard coatings. ***