Electron-beam-induced reactions at O2/GaAs(1 0 0) interfaces

We present a high resolution core-level photoemission study with synchrotron radiation, which illustrates the induced chemical reactions at O2/GaAs(1 0 0) interfaces upon irradiation with a 150 eV electron beam, for different current densities. A detailed line shape analysis of As(3d) and Ga(3d) levels allows us to identify the oxide phases formed, and to follow their evolution up to coverages of 10 إ. Equivalent amounts of Ga and As oxides are produced. The distribution of As oxides, in particular the As2O3/As2O5 oxide ratio, is found to depend on the electronic current density, whereas no differences are observed for Ga oxides. These changes are discussed in terms of the kinetic constraints introduced by the electron beam and the instability of the As2O5 species upon electron bombardment in vacuum.