Theoretical Scanning Tunneling Microscopy Images of the As Vacancy on the GaAs(110) Surface

The atomic and electronic structure of an As vacancy on the GaAs(110) surface is examined using ab initio pseudopotentials. The relaxed atomic structure reveals an inward movement of the neighboring surface Ga atoms which is in disagreement with recent interpretations of the scanning tunneling microscopy (STM) images for this system. However, a careful analysis of the wave-function character of the vacancy states, and the theoretical STM image, for this geometry yields excellent agreement with the experimental STM images.