A scanning tunneling microscopy study of the GaAs(112) surfaces
The GaAs(112)A and B surfaces were prepared by molecular beam epitaxy (MBE) and characterized in situ by scanning tunneling microscopy (STM). Both surfaces are unstable. On the (112)A surface five facets with the orientations (111), {110} and {124} appear, while on the ( )B surface four facets with the orientations ( )B, { } and ( )B were observed. In both cases, the facets form depressions covering the entire surface. In addition, total-energy calculations employing density-functional theory were carried out for these surfaces. For the (112)A surface a roof-like structure of {111} and {113} planes has the lowest calculated energy. According to the calculations, the ( )B surface forms under As-rich conditions a roof-like structure of { }B and { }B planes, and it decomposes under Ga-rich conditions into { 0} planes. The experimental and theoretical findings for the ( )B surface are in good agreement. The occurrence of {124}-facets on the (112)A surface was not taken into consideration in the calculations and needs to be investigated further.
scanning tunneling microscopy molecular beam epitaxy total-energy calculations structure gallium arsenide high-index surfaces