Surface transformations on annealed GaAs(001)

Studies on the surface evolution during vacuum annealing of GaAs(001) have been performed using scanning tunneling microscopy. The transition from an ordered (2×4)/c(2×8) reconstructed surface to an ordered mixed phase (2×6)/(3×6) reconstruction is observed as the annealing temperature is increased from 450 to 500°C. The transition to the high-temperature phase is mediated by a transient disordered state. We discuss the origin and role of this state. At higher annealing temperatures, T520°C, in the (2×6)/(3×6) phase, we find that terrace edges become unstable, and the surface evolves to a morphology similar to those observed in general pattern-forming systems. A mechanism based on diffusion-limited growth of surface vacancies is discussed.