Scanning tunneling microscopy studies of Si(111)-2x 1 surfaces

We have used scanning tunneling microscopy (STM) to study cleaved Si(1 _11) surfaces. On ordered regions of the 2x1 reconstruction we observe atomic rows with a [211] corrugation amplitude of typically 0.2 A and an [Ol 1 ] corrugation amplitude of < 0.02 A, consistent with the 7r-bonded chain model for this surface. Structural disorder is most commonly observed as protrusions along the chains and between chains. A second type of surface disorder is observed in the magnitude and asymmetry of the [211] corrugation amplitude, which we attribute to varying tilts and/or small translations of the 77-bonded chains. This latter type of disorder is enhanced in low-voltage images, indicating that the associated defect states have energies concentrated in or near the band gap of 2 X 1 surface-state energies. © 1986, American Vacuum Society. All rights reserved.