IMPERFECTIONS ON THE CHEMICALLY PREPARED, IDEALLY H-TERMINATED SI(111)-(1X1) SURFACES

A defect-induced feature in the Si-H stretch spectrum of chemically prepared H/Si(111)-(1 x 1) surfaces is studied with infrared absorption spectroscopy. These ideally H-terminated surfaces are characterized by a sharp Si-H stretch absorption band at approximately 2084 cm-1 , polarized perpendicular to the surface. In addition, a weak feature is observed approximately 0.9 cm-1 higher in frequency, even on the best surfaces. Its linewidth is very small (approximately 0.1 cm-1) and independent of that of the main Si-H stretch mode. This spectral feature is attributed to monohydrides located next to a defect, either structural (e.g. vacancy) or chemical (e.g. oxygen). Within this interpretation, model calculations indicate that the related defect density on the best samples ranges between 0.05% and 0.1% of a monolayer.