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Author: Loucas Loumakos
Requested Type: Either Oral or Poster
Submitted: 2015-03-27 16:33:39

Co-authors: Robert Ehlert,Michael C. Downer

Contact Info:
The University of Texas at Austin
1 University Station C1600
Austin, Texas   78712
United States of Ame

Abstract Text:
Step-edge rebonds and terrace dimers at vicinal Si(001) surfaces provide foundations for growth of nano-wires and epitaxial films, respectively. In-situ monitoring of these bonds is important for controlling growth of these structures. Although Raman and IR spectroscopy effectively fingerprint adsorbed molecules and substrate phonons, they are ineffective probes of surface Si-Si bonds. Here we fingerprint step rebonds and terrace dimers via the unique rotational anisotropy (RA) of their single-wavelength second-harmonic generation (SHG). Previously RA-SHG was used to monitor backbond-angle distortion at simple surfaces [Si(111)-1x1] with only 4 bonds per unit cell [1]. However, at complex surfaces such as vicinal Si(001), the identifying RA-SHG signature of a single bond of interest is usually lost in the background of competing bond responses. We show that strategic choice of incidence angle and input/output polarization combination enables a desired single-bond RA-SHG fingerprint response to “stand out from the crowd”. We demonstrate the method by monitoring atomic-hydrogen etching of step rebonds at 600K, and bonding of cyclopentene (C5H8) to terrace dimers via 2+2 cyclo-addition. Preliminary results on growth of STO on vicinal Si(001) will also be presented.