Atomic vibrational modes onGaAs(001)−β2(2×4)

Abstract

Atomic vibrational modes on the GaAs͑001͒-␤ 2 ͑2 ϫ 4͒ surface have been determined by applying a combination of the ab initio plane-wave pseudopotential method and a linear response scheme. It is found that the highest surface frequency mode lies at 8.74 THz and originates from the threefold coordinated Ga atom in the subsurface layer vibrating against its neighboring As atoms in the top and third layers. The As-As dimer stretch mode is found to lie at 6.33 THz. Energy locations and polarization characteristics of As-As dimer rocking and swinging phonon modes have also been identified and discussed.

Phonon spectrum and density of states onGaAs(001)−β2(2×4)

“…Only recently, we have calculated zone-center phonon modes for the As-rich GaAs͑001͒-␤ 2 ͑2 ϫ 4͒ surface using a linear response approach based on the density-functional and pseudopotential theories. 19 A full-scale surface phonon study is expected to be very valuable for obtaining additional signatures of surface reconstruction, for electron-phonon interaction, and for further studies related to phase transition and relaxation processes involving electronically or vibrationally excited states.…”