Stoichiometry study of S-terminated GaAs(001)-(2 × 6) surface with synchrotron radiation photoelectron spectroscopy

Synchrotron radiation photoelectron spectroscopy (SRPES) has been performed to investigate the surface stoichiometry of the S-terminated GaAs(001)-(2 × 6), and in particular, to determine the chemical species of the five dimers, which are separated by missing dimers and form the unit structure of the (2 × 6) reconstruction. The S 2p photoemission spectra show a significant decrease in the peak intensity with increasing substrate temperature, whereas no significant changes are observed for the As 3d photoemission spectra The Ga 3d spectra are decomposed into a bulk component and more than one surface component, one of which is attributed to a Ga-S bond and decreases in accordance with the change observed in the S 2p spectra. These results strongly support the model that each pair of the five dimers in the (2 × 6) reconstruction consists of S-S dimers.