The adsorption and diffusion of additional Pb adatoms on the 1/3 monolayer Si(111)-(√3 x √3)R30°-Pb surface were investigated by means of variable temperature scanning tunnelling microscopy. This surface experienced a reversible phase transition to (3×3) symmetry at a critical temperature, Tc, of 86K. Scanning tunnelling microscopic images, acquired below and above Tc, permitted the identification of the nature and adsorption sites of additional Pb ad-atoms. A careful analysis of the diffusion, in which the influence of the scanning tunnelling microscopy in the measurements was addressed and discarded, was performed at temperatures well below room temperature but above Tc. In this way, the activation energy and the pre-exponential factor for the surface diffusion of single Pb adatoms on the high temperature (√3 x √3)R30° phase were obtained. Attention was paid to the role played by the underlying (3×3) phase at these temperatures.

Surface Diffusion of Pb Single Adatoms on the Si(111)-(√3 x √3)R30°-Pb System. I.Brihuega, M.M.Ugeda, J.M.Gómez-Rodríguez: Physical Review B, 2007, 76[3], 035422