Two-Dimensional Electron Transport and Scattering in Bi(111) Surface States

The Bi(111) surface exhibits a pronounced surface state which acts as dominant transport channel for electric current. We performed in situ four-point probe resistance measurements for thin Bi(111) films on Si(001) to study electron scattering effects in this two-dimensional (2D) electron gas. The surface morphology was manipulated by additional deposition of Bi at 80 K. A linear increase of surface resistance was measured at extremely low coverage of less than 1 % of a bilayer (BL) and the slope gradually decreases with coverage up to about 0.5 BL. This behavior was qualitatively explained applying a simple picture of electron scattering at adatoms or small islands during the early stages of growth in Bi(111) homoepitaxy. Beyond 0.5 BL resistance changes periodically showing an antiphase correlation with roughness-induced LEED (00)-spot intensity oscillations, indicating the scattering of electrons at island edges.