Direct Measurement of the Polarization Dependence of Si(111)2×1 Surface-State Absorption by Use of Photothermal Displacement Spectroscopy

Abstract

The polarization dependence of midgap optical absorption (0.38-0.51 eV) by Si(111)2×1 single-domain surfaces has been measured directly by photothermal displacement spectroscopy. The absorption is strongest when the light is polarized perpendicular to the period-doubling direction of the 2×1 reconstruction and is reduced by at least 95% when the polarization is rotated by 90°. This result supports the $\pi$-bonded chain model of the Si(111)2×1 surface reconstruction.