THEORY OF SCANNING-TUNNELING-MICROSCOPY IMAGES OF OXYGEN-ADSORBED SI(100) SURFACES

Simulated scanning-tunneling-microscopy (STM) images of stable and metastable adsorption sites for the O atom on the Si(100) surface have been obtained by first-principles electronic-structure calculations within the local-density approximation. In the simulated STM images of both sites, the positions of O atoms are not seen directly, while the neighboring Si atoms are found to become bright spots. As for the metastable site, the bright spot originating from the surface Si atom moves when the polarity of the tip's voltage is reversed. This phenomenon is due to the electrostatic field of negatively charged O atoms.