Surface phonons of theSi(111):In−(4×1)and

K. Fleischer

¹

,

S. Chandola

²

,

N. Esser³

et al.

Abstract

The reversible phase transition of the Si͑111͒ : In-͑4 ϫ 1͒ 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.

Structure of Si(111)-In Nanowires Determined from the Midinfrared Optical Response

“…Results from many different experiments, as well as ab initio band structure calculations, agree that the structure is metallic, with the In atoms forming two parallel zigzag chains, which are separated by zigzag Si chains that resemble the -bonded chains of Sið111Þ-ð2 Â 1Þ [3][4][5][6][7][8][9][10][11][12][13][14]. The structure has three quasi-1D surface state bands, which disperse strongly and cross the Fermi level along the chain direction, and show only a weak dispersion perpendicular to the chain.…”

“…In Ref. [24] it was argued that the metallic RT phase arises from dynamic fluctuations between degenerate ground states, but recent photoemission [21] and Raman spectroscopy [11] results have cast doubt on this model. Total-energy calculations [13] of the hexagon and the trimer model for the LT phase concluded that an unambiguous identification of the internal structure of the ground state on energetic arguments is problematic.…”

Interwire coupling forIn(4×1)/Si(111) probed by surface transport

“…The MIT in the In/Si(111) system is the result of a balanced intra-and interwire coupling [7][8][9][10]. For instance, the metalinsulator transition is correlated with the appearance of the * tegenkamp@fkp.uni-hannover.de ×8 diffraction spots, i.e., with order between adjacent wires.…”

Surface phonons of the Si(111)-(7×7) reconstruction observed by Raman spectroscopy

“…Intrinsically surface-sensitive techniques, such as * geurts@physik.uni-wuerzburg.de high-resolution electron energy-loss spectroscopy (HREELS) [18][19][20] and helium atom scattering (HAS) [21,22], are the well-established experimental tools for analyzing surface lattice vibrations. In recent years, also Raman spectroscopy (RS) as an optical technique, traditionally widely used for investigating phonons in semiconductor bulk and multilayers, has been successfully applied to probe surface vibration modes of clean surfaces as well as ordered adsorbed (sub)monolayers [16,17,[23][24][25][26][27][28]. This development was facilitated by resonant enhancement of the excitation and by the enormous improvement of detection sensitivity.…”