A high-performance Auger spectrometer has been used to separate the bulk and interface contributions to the Auger spectra of the As/Si(100) interface. Combining these results with measurements of the photoelectron spectra of core levels shows that the Auger-parameter shifts between atoms at the interface and in the bulk elements are -0.64+0.04 eV for As and 0.68+0.04 eV for Si. The Augerparameter shifts are analyzed in terms of recent theoretical models that indicate that there is a small charge transfer of -0.2e from Si to As at the interface.

Aluminum films oxidized in oxygen atmosphere are widely used in magnetic tunneling junctions (MTJs). We have determined the oxidation depth of these films by Fourier transform infrared (FTIR) spectroscopy in reflection-absorption mode. The oxide/Al interfaces are found to be abrupt and the thickness of the oxide layer increases slowly with exposure to oxygen, after a rapid onset. These results provide a physical picture of observed changes in the magnetotransport of MTJs as a function of Al thickness and oxidation time. The results also agree well with the empirically found optimum oxide growth condition which yields a maximum magnetoresistance.

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Here we report on a C 60 -based material, namely one ordered monolayer of C 60 on Ag͑100͒. In this system, the C 60 molecules are close to the ionic state C 60 3Ϫ and the C 60 -C 60 distance is comparable to that of Cs 3 C 60 . The photoemission spectra of the LUMO-derived band clearly indicate a metallic character at room temperature, while below 120Ϯ10 K we observe a considerable reduction of density of states at the Fermi level. The electron-phonon coupling and the physical reasons for the observed behavior are addressed.