Abstract

The capability of the scanning tunneling microscopy (STM) and spectroscopy (STS) to probe the topography and electronic structure of surfaces and adsorbate layers with atomic resolution makes it a powerful tool in the study of surface chemistry (1). Here we use STM, STS, ultraviolet photocmission spectroscopy (UPS) and electronic structure calculations to study the long-standing problem involving the nature of the initial stages of the oxidation of silicon. There have been a large number of studies on this issue utilizing a great variety of techniques. However, not only is the mechanism of oxidation still unclear, but there is not even agreement on what kind of product(s) is formed. Several different configurations have been proposed for the oxygen-containing sites in the early stages of the reaction (2). They involve oxygen atoms saturating the dangling-bonds of top-layer Si atoms, oxygen atoms inserted in back-bonds but leaving the dangling-bonds intact, or molecular forms of oxygen attached to surface atoms or bridging two surface Si atoms.

© 1991 Optical Society of America