Interaction of Cl2 with GaAs(110) with and without laser irradiation

We have studied the interaction of Cl2 with a well-defined GaAs(110) surface under ultra-high vacuum conditions. When this surface is cooled to below 100 K, chlorine adsorbs dissociatively and in molecular form. Illumination of a Cl2-covered surface at 85 K with 193 nm laser light causes desorption of Cl atoms and the formation of AsCl3. Radiation at 351 nm forms a much smaller quantity of AsCl3 and desorbed Cl flux. Irradiation with a 535 nm laser produces no effect. We suggest that the surface reaction, in the case of 193 nm, is initiated by Cl2 dissociation through attachment of electrons, photoemitted from the substrate.