Controlling the Dynamics of a Single Atom in Lateral Atom Manipulation
Joseph A. Stroscio, Robert Celotta
We study the dynamics of a single Co atom during lateral manipulation on a Cu(111) surface in a low temperature scanning tunneling microscope. The Co binding site locations are revealed in a detailed image that results from lateral Co atom motion within the trapping potential of the scanning tip. Random telegraph noise, corresponding to the Co atom switching between hcp and fcc sites, is seen when the tip attempts to position the Co atom over the higher energy hcp site. We are able to control the dynamics of the Co atom by using the tip to modify the normal Cu(111) potential landscape, thereby controlling the residence time of the Co atom in these sites. We find two distinct regimes in our measurements of the transfer rates between the hcp and fcc sites. At low tunneling voltages below approximately 5 mV, we observe a transfer rate that is independent of tunneling voltage, current, and temperature. At higher voltages, the transfer rate exhibits a strong dependence on tunneling voltage, indicative of vibrational heating by inelastic electron scattering. These measurements extend both the scope and reliability of atom manipulation and assist in realizing a lateral atomic switch.