Applications of Surface Science 11/12 (1982) 249—267 249 North-Holland Publishing Company INTERACTION OF METALS WITH SEMICONDUCTOR SURFACES * L.J. BRILLSON Xerox Webster Research Center, 800 Phillips Road 114, Webster, New York 14580, USA Received 8 June 1981 Metal films on semiconductor surfaces produce strong atom and charge rearrangement at their microscopic interface which can be characterized on an atomic scale by soft X-ray photoemission spectroscopy (SXPS). For compound semiconductors, the presence of a metal film induces a substrate dissociation and diffusion of cation and anion into the metal. SXPS reveals that the magnitude and stoichiometry of this semiconductor outdiffusion depends systematically on the strength and nature of interface chemical bonding and that metal indiffusion also takes place. In addition, we have used monolayer thicknesses of reactive metal “interlayers” at metal film—semi- conductor substrate interfaces to modulate the chemical and electronic structure of the extended metal—semiconductor interface. 1. Introduction Over the past several years, there have been a rapid series of developments in the understanding of metal—semiconductor interfaces. A variety of ultrahigh vacuum (UHV) techniques have shown that atomic layers of metal can interact strongly with clean semiconductor surfaces, yielding in general regions of new chemical bonding [1—11] and/or interdiffusion at their interface [12—14].Such phenomena result in strong atom and charge rearrangement near the micro- scopic metal—semiconductor interface, even near room temperature. In turn, these effects are associated with new electronic states and Fermi level changes within the semiconductor band gap which correspond to the electronic barrier height of the bulk metal—semiconductor junction [1,5,6,12—22]. The direct relationship between microscopic and macroscopic properties emphasizes the importance of characterizing changes in atomic position and bonding at the local metal—semiconductor interface. Using soft X-ray photoemission spectros- copy (SXPS) to study atomic thicknesses of metal evaporated on semiconduc- tor surfaces cleaved in ultrahigh vacuum, we have characterized the chemical and electronic structure of the interface region on a monolayer scale. For * The work reported here was carried out in collaboration with R.S. Bauer, R.Z. Bachrach, C.F. Brucker, 0. Margaritondo, A.D. Katnani and N.G. Stoffel. 0378/5963/82/0000—0000/$02.75 © 1982 North-Holland