Microscopic structure of the GaAs(001)-(6×6) surface derived from scanning tunneling microscopy

We have derived a microscopic, structural model for the GaAs(001)-(6×{}6) surface reconstruction using scanning tunneling microscopy. It involves three atomic layers containing both As and Ga dimers. Previous studies suggested the (6×{}6) structure to be poorly ordered, often it was only described as a (1×{}6) superstructure. In contrast, we find a well-developed (6×{}6) superstructure with As-dimer rows in the [11{}0] direction separated by 24 {}. However, this reconstruction may not be a stable equilibrium structure.