Chemical applications of scanning tunneling microscopy

The development of a scanning tunneling microscope at the California Institute of Technology is well under way. Electron tunneling has been demonstrated, and preliminary surface images of gold films have been obtained. Additional instrumental development is required to achieve the atomic resolution which is required for the study of chemical processes on surfaces. A theoretical model is also being developed for the study of tunneling of electrons from the probe to surfaces with molecular species adsorbed, and with atomic and molecular species intervening between the probe and the surface. These experimental tools and theoretical models, which are being developed concurrently, will be applied to the study of chemical systems and processes on surfaces. Some of the first molecular species for study will include benzene and pyridine on metal surfaces, and porphyrins and phthalocyanines on pyrolytic graphite. The applications that can be imagined for STM in surface chemistry are very broad, and the choice of additional systems for study will be based on the results of these initial experiments.