High-resolution analysis of semiconductor surface phonons by Raman spectroscopy

Abstract

Only recently has Raman spectroscopy advanced into the study of surface phonons from clean and adsorbate-covered semiconductor surfaces. Raman spectroscopy allows one to determine the eigenfrequencies of zone-center surface phonons with high spectral resolution as well as symmetry selection rules. Moreover, surface electronic states become accessible via the electron–phonon coupling. To illustrate the potential of Raman spectroscopy we consider two examples: clean InP(110) and Sb-terminated Si(001) surfaces. For the clean InP(110) surface, two localized surface modes in the gap between acoustic and optical bulk branches together with a third one slightly above the bulk optical branches at the Γ-point are identified. Surface electronic transitions are detected in the resonance of the Raman scattering cross-section, i.e. by changing the energy of the exciting laser light. For Sb-monolayer-terminated Si(001) we find a surface phonon at 131 cm −1. By analyzing the selection rules of this surface phonon for singular and vicinal Si(001) we determine the ratio of (2×1):(1×2) Sb-dimer-terminated domain occupancies.