Surface Structures and Properties of Diamond-Structure Semiconductors

Low-energy electron-diffraction and secondary electron-emission measurements have been made on (111) and ($11\overline{1}$) surfaces of GaSb and (100) surfaces of InSb. To account for the diffraction patterns observed both for these materials and previously for Ge and Si, a general model for (111) surfaces of diamond-structure semiconductors is proposed. Every second atom, counting along alternate close-spaced rows is raised with respect to its neighbors, being bonded to the sublayer by three $p$ bonds while the "dangling bond" is $s$ type. The remaining three-fourths of the surface atoms have dangling $p$ bonds and are bonded to the sublayer by trigonal $s{p}^2$-type bonds.