ELECTRONIC CHARACTERIZATION OF DEFECT SITES ON SI(001)-(2X1) BY STM

A study of the defect sites on Si(001)-(2 x 1) was undertaken by emplo ying comparative scanning tunneling spectroscopy (CSTS). Ni induced de fects, the A, B, and C defects, and the A and B steps were studied. Th e STM tip induced band bending significantly affects tunneling spectra . This is evident from a comparison of LDOS and local surface potentia ls obtained for high (10 Omega cm) and low (100 Omega 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 channe l'' defect. In agreement with previous studies, a reduction in the sur face states energy gap was observed for the C defect. The B step and t he C terrace defect reveal similar LDOS. This is interpreted as indica ting 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 H2O decomposition. This may be responsible for preferential etching phenomena or evaporation at step edges. (C) 1997 Elsevier Sci ence B.V.