Double-resonant Raman processes in germanium: Group theory andab initiocalculations

We study the excitation-energy-dependent Raman peaks of germanium in terms of double-resonant scattering. In our analysis we combine group theory and ab initio calculations to select scattering processes and contrast them with the experimental data. A surface-driven k-selective mechanism explains not only the dependence of the peak shifts on surface orientation, but also their polarization dependence in a cubic system.