General Physics Seminar Thursday 13 December 2001 at 11.30


Surfaces in Action: The Atomic Slide Puzzle and other nano-Toys

Joost Frenken

Kamerlingh Onnes Laboratorium, Universiteit Leiden, The Netherlands


Scanning Tunneling Microscopy is used increasingly to investigate surface processes rather than structures. Two processes are in focus in the present talk. We use a high-speed, variable-temperature STM to study the two-dimensional random walks of surface vacancies in a metal surface. In order to visualize this motion, we alloy a low density of In atoms into the first layer of a Cu(001) surface, and use the embedded In atoms as tracer particles for the ultrafast, slide-puzzle type motion of the surface vacancies.

We have recently constructed a new STM, which is integrated in a high-temperature, high-pressure flow reactor. With this instrument we follow the atomic-scale structure of a metal surface during catalytic reactions. By analyzing the composition of the gasses that leave the reactor, we correlate the observed surface structures with the actual catalytic activity of the surface. The oxidation of CO on Pt(110) serves as a first example. Oxygen and CO strongly affect the surface structure, which, in turn, has dramatic consequences for the reaction between the two gasses.