Correlations between the scanning tunneling microscopy imaged configurations and the electronic structure on stepped Si(111)-(7 x 7) surfaces

We have observed the dependence of the scanning tunneling microscopy (STM) imaged atom intensity within the (7 x 7) unit cell on stepped Si(111) as a function of the tunneling voltage. Pronounced differences from the correspo nding atom intensity on the flat surface are observed for the contrast of a toms on the low versus the high side of the step and for the contrast betwe en the faulted versus unfaulted subcells of the (7 x 7) structure. These di fferences can be accounted for by changes in the electronic structure withi n the (7 x 7) subcells adjacent to the step. Calculations of the local dens ity of states and the STM images using a tight-binding method are in excell ent agreement with the experimental results.