When vibrational spectra are not enough: Using first-principles theory to identify adsorbate structures on silicon and diamond (100) surfaces

COLL 11

Douglas J. Doren, Danesha R. Fitzgerald, and Jeffrey Frey. Department of Chemistry and Biochemistry, University of Delaware, University of Delaware, Newark, DE 19716
The role of theory in identifying adsorbates on semiconductor surfaces will be described in two case studies. The first is addition of butadienes to Si(100) or diamond (100), where several reactions are kinetically possible and a mixture of products is expected. Some of these have nearly identical spectra, so vibrational spectroscopy is not able to determine the product distribution. STM can be used to distinguish the presence of different structures, as shown by simulated images. The second example concerns hydrogen on diamond (100). Theory predicts that the peak positions for symmetric and asymmetric stretch modes on the majority sites are significantly affected by intersite interactions. The splitting between these peaks is in good agreement with experiment, but the observations show a third peak, previously unidentified. Theory suggests that this peak be assigned to hydrogen at steps or other defects, where intersite interactions are diminished.