Studying the surface conductivity of a thallium bilayer on Si(111) substrate after adsorption of lithium and rubidium

Changes in the state of a thallium bilayer on Si(111) substrate, Si(111)6 $\times$ 6–Tl, after adsorption of lithium and rubidium were studied using low-energy electron-diffraction and four-point probe-conductivity measurements. New surface reconstructions 5 $\times$ 1 and 5$\sqrt3\times5\sqrt3$ were observed after the adsorption of lithium, and 2 $\times$ 2 and $\sqrt3\times\sqrt3$ reconstructions appeared after the adsorption of rubidium. The surface conductivity of silicon substrates was studied as a function of the dose of deposited adsorbate. It is established that the formation of both 5 $\times$ 1 and 2 $\times$ 2 reconstructions retains the conducting properties of a two-dimensional channel constituted by the thallium bilayer.