ELECTRON-ENERGY-LOSS STUDY OF AG-GAAS(110) AND AU-GAAS(110) INTERFACES

A high-resolution electron energy loss investigation of the Ag- and Au -GaAs(110) interfaces is presented. The loss spectra (0.5 less than or equal to E(loss) less than or equal to 5 eV) show clearly a broad fea ture centred at 1.2 eV, that is within the energy gap, due to the meta l coverage. This structure, which starts appearing at coverages as low as 0.1 Angstrom, becomes undetectable at coverages of 24 Angstrom of Ag and 1.6 Angstrom of Au. The gap energy region has been examined on several freshly cleaved surfaces. In the case of bad cleaveges, a peak similar to that induced by the metal overlayer develops, a fact which supports mechanisms ascribing the Fermi level pinning to defect state s.