The polarization dependence of surface-state absorption of Ge(111)2 x 1 single-domain surfaces was directly measured using photothermal displacement spectroscopy. The absorption at 0.5eV was maximum for incident light polarized perpendicular to the period-doubling direction of the 2 x 1 reconstruction. As the polarization direction was rotated, the absorption follows a cos2θ dependence. This result supports the π-bonded chain model for the surface reconstruction, and was the same as that reported for the dangling-bond absorption of Si(111)2 x 1.

Polarization Dependence of Ge(111)2 x 1 Surface-State Absorption using Photothermal Displacement Spectroscopy - a Test of Surface Reconstruction Models. M.A.Olmstead, N.M.Amer: Physical Review B, 1984, 29, 7048-50