High-resolution analysis of semiconductor surface phonons by Raman spectroscopy

Only recently has Raman spectroscopy advanced into the study of surface pho nons from clean and adsorbate-covered semiconductor surfaces. Raman spectro scopy allows one to determine the eigenfrequencies of zone-center surface p honons with high spectral resolution as well as symmetry selection rules. M oreover, surface electronic states become accessible via the electron-phono n coupling. To illustrate the potential of Raman spectroscopy we consider t wo examples: clean InP(110) and Sb-terminated Si(001) surfaces. For the cle an InP(110) surface, two localized surface modes in the gap between acousti c and optical bulk branches together with a third one slightly above the bu lk optical branches at the Gamma-point are identified. Surface electronic t ransitions are detected in the resonance of the Raman scattering cross-sect ion, i.e. by changing the energy of the exciting laser light. For Sb-monola yer-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 x 1):(1 x 2) Sb-dimer-terminated domain occu pancies. (C) 1999 Elsevier Science B.V. All rights reserved.