Photon-assisted oxidation of the GaAs(100) surface using water at 90 K

Photoelectron spectroscopy is used to study the interaction of H2O with GaAs(100) at 90 K and to assess its use as a photon-assisted oxidizing agent. The condensation of H2O at 90 K produces a thin physisorbed layer on GaAs(100). We found that intense synchrotron radiation causes most of the water to desorb in a sequential manner, without reacting with the substrate. The fraction of water that does not desorb reacts with Ga, giving rise to a Ga oxide. The As present in the substrate does not react with H2O during the process, thereby avoiding the formation of volatile As compounds.