Scanning Tunneling Microscopy of (NH4)2Sx-Treated GaAs Surfaces Annealed in Vacuum

Abstract
The atomic structure of (NH4)2S x -treated and annealed GaAs surface is revealed using scanning tunneling microscopy (STM). STM image observation reveals that the GaAs surface is terminated with Ga–S bonds and that the monolayer sulfur forms dimers. Surface structural parameters such as S–S dimer bond length and Ga–S distance in the [100] direction are determined. STM measurements reveal that the surface is covered not only with an S monolayer but also with an S multilayer even with high-temperature annealing at 510°C.