Core-level photoemission investigation of atomic-fluorine adsorption on GaAs(110)

The adsorption of atomic F on the cleaved GaAs(110) surface has been studied with use of high-resolution core-level photoelectron spectroscopy by exposing the GaAs(110) surfaces to ${\mathrm{XeF}}_2$, which adsorbs dissociatively, leaving atomic F behind. This surface reaction produces two chemically shifted components in the Ga 3d core-level emission which are attributed to an interfacial monofluoride and a stable trifluoride reaction product, respectively. The As 3d core level develops only one chemically shifted component and from its exposure-dependent behavior it is attributed to an interfacial monofluoride. Least-squares analysis of the core-level line shapes revealed that (i) the F bonds to both the anion and the cation , (ii) the ${\mathrm{GaF}}_3$ component (characteristic of strong interfacial reaction) and the surface core-level shifted component (characteristic of a well ordered, atomically clean surface) are present together over a relatively large range of ${\mathrm{XeF}}_2$ exposures, and (iii) it is the initial disruption of the GaAs(110) surface that is the rate-limiting step in this surface reaction. These results are compared with similar studies of Cl and O adsorption on GaAs(110).