Alteration of the inter-chain distance between Au atomic wires on Si(111) induced by Tl adsorption

Abstract

Thallium (Tl) deposition onto the Au/Si(111)5 × 2 reconstruction followed by annealing at about 300 °C has been found to result in the formation of the surface structure having 4 × 2 periodicity. Similar to the most reconstructions in the (Au, Tl)/Si(111) system, Au and Tl do not intermix uniformly. While Au chains preserve their inner structure, Tl atoms being highly mobile at room temperature continuously migrate over the Si chains. Thallium donates electrons into the surface, that results in the two consequences: (i) filling the originally partially filled surface-state band, thus converting the metallic surface into an insulating state; (ii) transforming Si chains, which separate Au atomic rows, from the honeycomb-like to the zigzag according to the electron counting rule. The latter alters the inter-chain distance within the array of Au atomic wires. Au and/or Si chains contain point defects, which are masqueraded by the mobile Tl atoms producing peculiar “wavy” STM images.