Origin of symmetric STM images for the asymmetric atomic configuration on GaAs(001)-c(4 × 4)α surfaces

The empty-state scanning tunneling microscopy (STM) images of GaAs-c(4 × 4)α show symmetric features at positive biases, contrary to the naive prediction based on electron counting model. In this paper, we report that STM simulations based on first-principles electronic structure calculations successfully demonstrate symmetric images consistent with the STM observations. Furthermore, simple analysis has revealed that the origin of the symmetric images is the combined local electron density of multiple orbitals, and is essentially different from those on GaAs-c(4 × 4)β surfaces.