PROBING AND INDUCING SURFACE-CHEMISTRY WITH THE STM - THE REACTIONS OF SI(111)-7X7 WITH H2O AND O2

We discuss the applications of scanning tunneling microscopy and spectroscopy to both probe and induce surface chemistry with atomic resolution. The reactions of Si(111)-7 x 7 with H2O and O2 are considered. In the case of the H2O reaction, we find a site selectivity consistent with a dominant dissociative chemisorption mechanism. In the case of the oxidation reaction we image two distinct oxygen containing species being formed in the early stages of oxidation. With the help of electronic structure calculations we are able to identify the nature of these species and propose an oxidation mechanism. Through the combined effects of strong electric fields and chemical interactions between the STM tip and individual adsorbates on the H2O-exposed surface at close range, we are able to remove individual absorbates and thus restore local reactivity.