AVS 51st International Symposium
    Surface Science Monday Sessions
       Session SS1-MoM

Paper SS1-MoM4
Listening to Atom Dynamics During Atomic Manipulation

Monday, November 15, 2004, 9:20 am, Room 210B

Session: Electronic Structure and Excitations
Presenter: J.A. Stroscio, National Institute of Standards and Technology
Authors: J.A. Stroscio, National Institute of Standards and Technology
R.J. Celotta, National Institute of Standards and Technology
Correspondent: Click to Email
The physics of atomic manipulation with the scanning tunneling microscope (STM) involves many processes that depend on the tip-adatom interaction. We discuss our work on using atom manipulation imaging and the noise characteristics of the tunneling current as probes of the physics of the atomic manipulation process. By scanning a single Co atom across a Cu(111) surface, along the same path we would use to image the Cu surface, we can obtain a highly detailed image, showing three distinctly different atom binding sites. If the Co atom is positioned over an hcp site, dynamic behavior is observed both in the STM image and the tunneling current. The site dependent noise in the tunneling current is in the audio range and can be heard as the atom is dragged over the surface. We show that this dynamic behavior corresponds to state fluctuations of the Co atom; the Co hops between the hcp site and adjacent fcc sites. This occurs by the creation of an ideal, tunable, multi-well potential by the tip-adatom interaction. An ideal double-well potential can be created by positioning the Co atom slightly off the hcp site. Two-state transfer rates between the hcp and fcc sites are obtained by measuring the distribution of residence times in each state. The transfer rates show two distinct regimes. A transfer rate independent of tunneling current, voltage and temperature that is ascribed to quantum tunneling between the two wells, followed by a transfer rate with a strong power law dependence on current or voltage, indicative of vibrational heating. The role of these effects in atomic manipulation applications will be discussed.