Surface structures of compound semiconductors

Abstract

A survey is given of surface-structure determinations for the low index faces of compound semiconductors via analyses of elastic low-energy electron diffraction intensities. The (100) face of (cubic-NaCl structure) MgO is thought to exhibit a surface structure that differs little from that of a truncated bulk crystal. Small deviations from the truncated bulk geometry have been reported for the layered transition-metal dichalcogenides MoS2 and NbSe2. The cleavage faces of tetrahedrally coordinated compound semiconductors [i.e., zincblende (110), wurtzite (101̄0), and wurtzite (112̄0)] exhibit the same space-group symmetry as the bulk crystal. The positions of the species in the uppermost atomic layer may be altered substantially from their bulk values, however, with the anion shifted outward, the cation inward, and the whole layer relaxed toward the bulk crystal. For the materials examined to date [i.e.,GaAs(110), ZnSe (110), ZnO(101̄0) and ZnO(112̄0)] the shifts in atomic position vary in magnitude but can exert profound effects on the electronic structure and chemical behavior of the associated surfaces.