Force, current and field effects in single atom manipulation

We present a detailed investigation of the manipulation of Ag and Au atoms with a STM tip on the Ag(111) surface at 5K. The interpretation of the feed-back loop signal gives a precise picture of the movement of the atom during manipulation. The threshold tunnelling resistance and tip-height to move a Au/Ag atom have been determined using automated manipulation measurements. The results show that at low biases chemical forces dominate in the manipulation process. Above ±70 mV tunnelling voltage Au atoms start to move already at greater tip-atom separation, which can be attributed to a current effect. Tip-induced diffusion was used to measure the influence of the electric field which can be ruled out at low biases. ©2003 American Institute of Physic