Scanning tunneling microscopy of cleaved semiconductor surfaces

Scanning tunneling microscopy is used to study the surface topography of cleaved GaAs(110) and Si(111) surfaces. For GaAs we observe 1 × 1 periodicity, with an [001] corrugation amplitude of typically 0.2 Å and a [̅110] corrugation amplitude of ~0.05 Å. Surface point defects are observed, consisting typically of ∼0.7-Å-deep depressions extending along the rows. For Si(111), we find a periodicity of two unit cells, indicating the presence of the 2 × 1 reconstruction. We observe a maximum [2̅1̅1] corrugation amplitude of 0.5 Å and a [011] corrugation amplitude of <0.02 Å, consistent with the π-bonded chain model for this surface. Structural disorder on the surface most commonly appears as “protrusions” along or crossing over between the chains. Orientational disorder is observed in the tilt of the chains.