Electron-beam-induced reactions at O-2/GaAs(100) interfaces

We present a high resolution core-level photoemission study with synchrotro n radiation, which illustrates the induced chemical reactions at O-2/GaAs(1 0 0) interfaces upon irradiation with a 150 eV electron beam, for differen t current densities. A detailed line shape analysis of As(3d) and Ga(3d) le vels allows us to identify the oxide phases formed, and to follow their evo lution up to coverages of 10 Angstrom. Equivalent amounts of Ga and As oxid es are produced. The distribution of As oxides, in particular the As2O3/As2 O5 oxide ratio, is found to depend on the electronic current density, where as no differences are observed for Ga oxides. These changes are discussed i n terms of the kinetic constraints introduced by the electron beam and the instability of the As2O5 species upon electron bombardment in vacuum. (C) 2 001 Elsevier Science B.V. All rights reserved.