Secondary ion mass spectroscopic studies of the atomic geometry of GaAs(110)

Abstract

The atomic geometry of the GaAs(110) surface has been determined by shadow-cone enhanced desorption. Ga+ secondary ion yields were analyzed without extensive calculations or assumptions of structure except that the second and all lower layer atoms are at bulk lattice sites. The structure determined from this simple analysis shows excellent qualitative agreement with most preceding models. The surface As atomic position is determined to be displaced laterally 1.28 Å toward the second layer Ga atom and is relaxed away from the surface by 0.69 Å, while the surface Ga atom is displaced 0.37 Å laterally in the same direction as the As atom and compressed 0.45 Å toward the surface. The resulting chain rotation is 29.3° and both surface As bond lengths are determined to be lengthened. A detailed discussion of the shadow-cone enhanced desorption method of structure analysis is presented along with areas of possible refinement. Also presented is a description of our experimental apparatus which was developed for the in situ characterization of molecular-beam epitaxially grown surfaces.