Surface structure and composition of β- and 6H-SiC

Abstract

The composition and structure of the (001) and (111) surfaces of β-SiC, and the (0001) surface of 6H-SiC, have been studied using low energy electron diffraction, and Auger and energy loss spectroscopies. The (001) orientation exhibited five distinct phases: the 3 × 2, c(4 × 2), 2 × 1, c(2 × 2), and 1 × 1. New models for some of these phases are proposed. It is suggested that ordering of asymmetric dimers is responsible for the c(4 × 2) and 3 × 2 structures. The c(2 × 2) manifested altered bonding at the surface, implying that the usual dimerization was absent. Results for the (111) and (0001) surfaces were indistinguishable, consistent with the crystal structures of these polytypes and the penetration depth of the electron beams used in the measurements. Three distinct phases were observed for these orientations: 3 × 3, (√3 × √3)R30°; and 1 × 1. The 3 × 3 is identified with an adsorbed Si bilayer, and is believed to be a member of the N × N class of reconstructions common to Si and its alloys.