Dr. Marcus McEllistrem
Chemistry occurring on solid (often crystalline) surfaces.
Surface reactions monitored on the 'macro' scale
Reactions followed on the atomic scale.
As an example, the chemistry of hydrogen on silicon surfaces has been studied in some detail, using a variety of techniques.
It is possible to image the motion (diffusion) of hydrogen on silicon at the atomic scale using a scanning tunneling microscope (STM), which can take an image in about 18 seconds, operated at an elevated temperature.
Shown here is a brief movie made from individual frames taken with an STM. It shows a silicon surface mostly covered with hydrogen atoms and heated to 300 C. The bright moving features actually are places where the hydrogen is absent. Pairs of vacancies are stable, but unpaired vacancies can diffuse. Note the pair of vacancies (at center top) that start paired, then unpair and later pair again. Other lone vacancies simply wander during the course of the movie.
For a detailed discussion, see:
"Dangling Bond Dynamics on the Si(100)-2x1 Surface - Dissociation, Diffusion and Recombination", M. McEllistrem, M. Allgeier, and J.J. Boland, Science 279 (1998) 545.
last updated Jan. 2003
[College of A&S] [Chemistry Department] [Chemistry Faculty]