Dynamics of the 7 x 7 DAS-reconstructed Silicon (111) Surface

TL;DR

This paper investigates the dynamics of the reconstructed Si (111) surface using a vibrational-spectrum approach based on tight-binding Hamiltonian, revealing key surface features and vibrational interactions.

Contribution

It introduces a method combining supercell optimization, Green's function, and a decomposition scheme to analyze surface vibrational dynamics of Si (111).

Findings

Identified surface dynamical features of dimers, adatoms, stacking faults, and rest atoms.

Developed a scheme to directly identify coupled vibrations.

Provided detailed vibrational spectra for the reconstructed surface.

Abstract

We studied the dynamics of the reconstructed Si (111) surface using a total-energy-vibrational-spectrum approach based on a non-orthogonal tight-binding Hamiltonian. We first established the size of the supercell sufficient to yield a reliable determination of surface parameters by the structural optimization. The site density of vibrational states (SDOS) for the semi-infinite system (the optimized slab on top of the bulk) was then calculated using the method of real space Green's function. A decomposition scheme for the SDOS that identifies directly coupled vibrations for a given mode was also proposed. Our study has uncovered and elucidated, for the first time, all the important surface dynamical features associated with the dimers, adatoms, stacking faults, and rest atoms.