Scanning tunneling microscopy study of the evolution of the GaAs(001) surface during the (2 × 4)−(4 × 2) phase transition

Evolution of the GaAs(001) surface during the transition from the As-rich 2 × 4 to the Ga-rich 4 × 2 phase has been studied by scanning tunneling microscopy (STM). It was found that the (2 × 4) → (4 × 2) transition proceeds via the formation of intermediate multi-domain phases exhibiting 3 × 6 and 4 × 6 low-energy electron-diffraction (LEED) patterns. The STM images reveal that the 3 × 6 phase is composed of regions of the ‘2 × 6’ and another phase with no long-range order, while the 4 × 6 phase in addition contains 4 × 2 domains. A new structural model for the ‘2 × 6’ phase based on the analysis of high-resolution dual polarity bias STM images is proposed.