Adsorption and tunneling of atomic scale lines of indium and lead on Si(100) - art. no. 115402

The atomic resolution capability of scanning tunneling microscopy is used t o reveal interesting similarities and differences on the adsorption and tun neling behavior of In and Pb on Si(100). While both metals form one-dimensi onal ad-dimer chains on Si(100), In dimers are symmetric but show sharp con trasts between filled and empty states whereas Pb dimers give similar contr asts for both polarities but are buckled. The charge transfer accompanying the buckling of Pb dimers is imaged selectively for charged Pb atoms at dif ferent bias polarities within a dimer. The contrast mechanism of dimer chai ns is rationalized through a simple picture of spatial orbital extension in to the tunneling gap. On the other hand, tunneling spectra show a surface-s tate band gap of similar to1.2 eV for both In and Pb chains and the resulta nt absence of length dependency. However, the localized surface states of I n chains near the gap are different from those of Pb chains due to the diff erence in their electronic configurations. Systematic analysis of the local maxima in tunneling density of states and their relations to the surface-s tate bands induced by metal-metal and metal-silicon interactions will also be presented.