Electronic characterization of defect sites on Si(001)-(2 × 1) by STM

Abstract

A study of the defect sites on Si(001)-(2 × 1) was undertaken by employing comparative scanning tunneling spectroscopy (CSTS). Ni induced defects, the A, B, and C defects, and the A and B steps were studied. The STM tip induced band bending significantly affects tunneling spectra. This is evident from a comparison of LDOS and local surface potentials obtained for high (10 Ω cm) and low (100 Ω cm) doped Si(001) crystals. Decay in the local surface potential was found around the Ni induced “split off dimer” defect site and in the “vacancy channel” defect. In agreement with previous studies, a reduction in the surface states energy gap was observed for the C defect. The B step and the C terrace defect reveal similar LDOS. This is interpreted as indicating that the C defect on the terraces migrates preferentially to the B step edge, and that it is due to a surface impurity such as Cl or a product of H 2O decomposition. This may be responsible for preferential etching phenomena or evaporation at step edges.