STM and SEM studies on the character of triangular Si(111)-7 × 7 domains formed in quenched Si(111) surface

Abstract

STM and SEM observations have been made on the 7 × 7 ordering process of quenched Si(111)-1 × 1 surface and on quenched metastable atom complexes. All the triangular 7 × 7 domains nucleated in the 1 × 1 region have been found to have character 〈1̄1̄2〉. The rate-controlling process for the growth is the nucleation of a faulted half cell at the outermost edge of the triangular domain. Corner holes, instead of dimer rows play a critical role for the nucleation of the faulted half cell. The contrast of STM filled state images have been examined on the quenched complexes; it is dark for the centered adatoms of 9 × 9 and 11 × 11, and for all the adatoms of 2 × 2, c(2 × 4) and a defected half of unfaulted type which was found for the first time in the present work. In contrast with these complexes, the adatoms of √3 × √3 structure appear bright. These features are interpreted in terms of the charge transfer (between the adatoms and rest atoms) mechanism. Extreme stability has been noted for a triangular defect region of 1 × 1 (with side a) in quenched Si(111) and has been attributed to the domain boundaries running from the apices of the triangular defect. The stability has been analysed quantitatively in terms of the energy versus a curve derived in this paper.