Characterization of chemically prepared Si-surfaces by uv-vis and IR spectroscopic ellipsometry and surface photovoltage

Abstract

Roughness and oxide coverage of silicon (Si) surfaces after various chemical treatments were investigated using ex situ spectroscopic ellipsometry (SE) both in the ultraviolet-visible (uv-vis) and in the infrared (IR) spectroscopic region. For control and optimization of electronic interface properties the large-signal field-modulated surface photovoltage technique was used for contactless measurement of the surface band-bending and the energetic distribution of interface states D it( E). Applying a special hydrogen (H)-termination procedure, very smooth Si(111) surfaces without any native oxide coverage were prepared, characterized by a U-shaped intrinsic surface state distribution and very low surface state density D it.min < 3 × 10 10 cm −2 eV −1. On these surfaces the resonant absorbance due to the SiH bonds was observed directly by IR ellipsometry. By comparing the SE data and interface state distributions of differently treated silicon surfaces the density of intrinsic and extrinsic surface states was correlated to the surface roughness and oxide coverage.