A method for the quantitative determination of tip effects, upon surface diffusion during scanning tunnelling microscopy, was presented. By using the atom-tracking technique, measurements were made of the bias voltage and tunnelling current dependences of adsorbed Si-dimer dynamics on Si(001). The activation barrier to diffusion varied by less than 3% over the range of typical tunnelling conditions. A marked difference was found between the electric-field effects upon dimer diffusion and rotation, thus indicating the importance of transition states in this system.

Direct Measurement of Field Effects on Surface Diffusion J.M.Carpinelli, B.S.Swartzentruber: Physical Review B, 1998, 58[20], R13423-5