Surface-Induced Optical Anisotropies of Single-Domain(2×1)Reconstructed (001) Si and Ge Surfaces

We report surface-induced optical anisotropy spectra of clean $\left(2\times 1\right)$ reconstructions of (001) Si and Ge surfaces, using oxygen exposure to separate contributions from dimers and steps. For Ge, the line shape is relatively simple and collapses uniformly with oxygen exposure. For Si, the results are more complicated and H termination must be considered as well. The clean-surface data of both Si and Ge are incompatible with a purely surface-to-surface transition model.