Surface phonons of the Si(111):In-(4 x 1) and (8 x 2) phases

Abstract

The reversible phase transition of the Si(111):In-(4?1) surface has been studied using Raman spectroscopy and the symmetry, frequencies, and linewidths of the surface phonon modes have been determined. Dramatically different behavior has been identified for vibrational motion in the direction of the In chains and orthogonal to them. The differences in the Raman spectra of the room and low temperature surface are discussed in terms of the Peierls transition model and a recent dynamical soft shear distortion model. The measurements are found to be consistent with the former model, while some difficulties arise for the latter model. A combined Peierls transition and soft shear distortion model is consistent with the data, but is lacking detail. The Raman spectra presented here represent a challenge in developing theoretical models of this complex system.