IMAGING AND MOVING A XENON ATOM ON A COPPER (110) SURFACE WITH THE TIP OF A SCANNING TUNNELING MICROSCOPE - A THEORETICAL-STUDY

The sliding of a xenon atom on a Cu(110) surface caused by a scanning tunneling microscope (STM) tip is discussed. Initially, the stable height and lateral position of a Xe atom on Cu(110) in the absence of the tip is calculated by considering Born-Mayer repulsive and van der Waals interactions. Using this geometry, a constant-current STM image of the Xe atom is then calculated using the STM-ESQC technique. For I = 1 nA and V = 10 mV, a bump of 1.7 angstrom is found, which is in good agreement with experiments. The stability of the Xe atom under the tip apex as a function of the tip to substrate distance is also discussed. At each tip height, the tunnel current intensity is calculated. The threshold tunnel resistance required to move a Xe atom with the tip is deduced from these calculations and is in good agreement with the experimental one. It is argued that the sliding process is due to the trapping of the Xe atom in a van der Waals well created by the tip apex. This trap is moved along the (110BAR) rows as the tip scans.