CPM Seminar

Atom Manipulation and Measurement of Atom Motion in Atomically Engineered Molecular Nanostructures

Joseph Stroscio

NIST Gaithersburg

The exciting ability to manipulate single atoms with the scanning tunneling microscope (STM) stirs our imaginations because of the possibilities that exist in building unique nanostructures with the capability of manipulating the basic building blocks of matter. In this talk I show that by “listening” to the atom motion, we can learn a great deal about the various interactions that come into play in atom manipulation, and probe the dynamics of atomically engineered molecular nanostructures [1]. “Listening” involves the measurement of the noise properties of the tunneling current in the STM tunnel junction. In atom manipulation the tunneling noise dynamics reveal a rich variety of physics contributing to the atom manipulation process, involving quantum tunneling and vibrational excitation mechanisms. Using tunneling noise spectroscopy, the quantum yield for exciting the motion of a single atom within a molecular nanostructure was measured with atomic spatial resolution. The molecular nanostructures consisted of a series of CoCun and CoCunCo linear molecules fabricated on a Cu(111) surface. The Co atoms at the end of the molecules were induced to switch between two lattice positions using electron excitation in a scanning tunneling microscope (STM). Above an electron energy threshold, the Co atom motion resulted from a predominantly single electron process. By systematically varying the molecular structure, atom motion within the molecule was shown to be dependent on molecular length and composition.

[1] J.A. Stroscio and R. J. Celotta, Science 306, 242 (2004).