Local-order of chemically-prepared GaAs(1 0 0) surfaces

In the present work HCl–propanol treated and vacuum annealed GaAs(1 0 0) surfaces were studied by means of soft X-ray photoemission and reflectance anisotropy spectroscopies (SXPS, RAS). On the as-treated surface, As 3d and Ga 3d core level spectra (CLs) are found to be similar to the ones observed on As-capped GaAs(1 0 0) surfaces after annealing at 350 °C, which desorbs most of the overlayer. RAS measurements of the as-treated surface and after annealing up to 350 °C show spectra similar to those detected on the as-grown surfaces with c(4×4) reconstruction. Anneals in the 380–470 °C temperature range lead to the appearance of a RAS line at 3 eV which is characteristic of As dimers. This finding coincides with the presence of a surface component in the As 3d core level spectrum with a chemical shift of −0.5 eV, which we attribute to As-dimers. Further annealing at 540 °C yields in RAS spectra an intense line at 2.2 eV due to Ga dimers, while the Ga 3d CLs do not exhibit any appreciable change.