AVS 52nd International Symposium
    Surface Science Tuesday Sessions
       Session SS1-TuA

Paper SS1-TuA5
SiO/GaAs Charge Build Up Induced Pinning

Tuesday, November 1, 2005, 3:20 pm, Room 202

Session: Compound Semiconductors
Presenter: D.L. Winn, University of California, San Diego
Authors: D.L. Winn, University of California, San Diego
M.J. Hale, University of California, San Diego
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The correlation between atomic bonding sites and the electronic structure of SiO on GaAs(001)-c(2x8)/(2x4), was investigated using scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and density functional theory (DFT). At low coverage, STM images reveal that SiO molecules bond Si-end down; this is consistent with Si being under-coordinated and O being fully-coordinated in SiO. At ~5% monolayer (ML) coverage, multiple bonding geometries were observed. To confirm the site assignments from STM images, DFT calculations were used to estimate the exotherimicties of the different bonding geometries. However, the sites predicted to be most stable were not the most abundant sites observed in the STM experiments. To rectify the discrepancy between calculations and experiments, a total energy vs. SiO chemical potential plot (i.e. SiO coverage) was constructed. Once the bonding geometries were deduced, STS measurements were preformed, which showed that SiO pins the Fermi level at ~5% ML coverage. Density of state (DOS) and partial density of state (PDOS) calculations revealed that only certain bonding geometries pin the Fermi level.