The dynamics of single vacancies on Ge(111)-c(2x8) surfaces were investigated by means of variable temperature scanning tunneling microscopy. These vacancies were deliberately created with the scanning tunnelling microscope at different sample temperatures by slight tip-sample contacts. The activation energies and the pre-exponential factors for the surface diffusion of the created vacancies were measured, finding that it was a thermally activated motion that presented a slight anisotropic behavior. The activation energy barrier obtained along the [1¯10] direction was 0.83eV, while along [¯1¯12] it was 0.95eV. The origin of such anisotropy was considered in terms of previous experimental results measured only at room temperature as well as previous first-principle calculations of the pristine Ge(111)-c(2x8) surface. Finally, the vacancy extraction procedure was investigated in a wide temperature range and it was shown for the first time that it was possible to create single vacancies at temperatures as low as 40K.

Surface Diffusion of Single Vacancies on Ge(111)-c(2x8) Studied by Variable Temperature Scanning Tunneling Microscopy. I.Brihuega, O.Custance, J.M.Gómez-Rodríguez: Physical Review B, 2004, 70[16], 165410 (8pp)