Atomic structure of the (formula presented) surface under As flux

The α, β, and γ phases of the (formula presented) surface have been studied using rocking-curve analysis of reflection high-energy electron diffraction (RHEED) and reflectance difference spectroscopy (RDS). We have measured RHEED rocking curves and RD spectra from GaAs(001) under an As flux of (formula presented) and have identified the temperature ranges where each of the α, β, and γ phases is stable. The (formula presented) reconstruction was observed in the range of 480-600 °C. The β phase, which is stable in the range of 510-550 °C, has a β (formula presented) structure, in good agreement with previous experimental and theoretical results. The γ and α phases are stable below 510 °C and above 550 °C, respectively. While the data from the γ phase are well explained by a mixture of β (formula presented) and (formula presented) phases, we propose that the α phase has a β (formula presented) structure, the atomic coordinates of which are slightly different from those of the β phase.