SURFACE RECONSTRUCTIONS OF INSB(100) OBSERVED BY SCANNING-TUNNELING-MICROSCOPY

A number of surface reconstructions formed on InSb(100) have been observed with atomic resolution using scanning tunneling microscopy (STM). Cycles of low-energy ion bombardment and annealing result in the formation of an In-rich surface with a c(8×2) diffraction pattern. Filled-states images of this indicate a (4×1) periodicity arising from imaging occupied lone-pair orbitals on exposed second-layer Sb atoms. The controlled deposition of Sb4 from a Knudsen effusion source onto the c(8×2) surface at elevated temperatures led to the formation of a (1×1), c(4×4), and an asymmetric (1×3) structure, in order of decreasing Sb/In ratio. Filled- and empty-states STM images of all these Sb-rich reconstructions were generated and the coexistence of the different structures was also observed. Both the (1×1) and asymmetric (1×3) surfaces showed a high degree of disorder while the c(4×4) surface was highly ordered. The c(4×4) structure, which involves the chemisorption of Sb onto an already Sb-terminated surface, is characterized by blocks of three pairs of well-resolved Sb dimers. Structural models are proposed for the ordered structures observed. © 1994 The American Physical Society.