AVS 59th Annual International Symposium and Exhibition
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP21
Methanol Induced Nanopatterning of Si(111):H – Insights from Density Functional Calculations

Tuesday, October 30, 2012, 6:00 pm, Room Central Hall

Session: Surface Science Poster Session
Presenter: P. Thissen, University of Texas at Dallas
Authors: P. Thissen, University of Texas at Dallas
T. Peixoto, University of Texas at Dallas
K. Roodenko, University of Texas at Dallas
E. Fuchs, Zyvex Labs LLC
W.G. Schmidt, University of Paderborn, Germany
Y.J. Chabal, University of Texas at Dallas
Correspondent: Click to Email
The reaction of methanol with hydrogen terminated Si(111) surfaces has been studied using density functional theory (DFT). Depending on the chemical potentials of hydrogen and methanol several surface configurations with various coverage are found to be stable. The temperature dependence of the chemical potentials as well as the entropy contributions to the surface free energy are found to result in only minor changes of the calculated surface phase diagram. In contrast, the calculated reaction barriers are found to be strongly dependent on the methoxy coverage of the surface. They strongly increase with increasing methoxy coverage. Our calculations thus suggest that the formation of a nanopatterned Si(111) surface, featuring 1/3 methoxy and 2/3 hydrogen termination as observed experimentally is related to the reaction kinetics rather than the surface thermodynamics. Consequently, we show that higher temperatures are the key parameter to prepare Si(111) surfaces with higher methoxy-group coverage than 1/3. Finally, a Kinetic Monte Carlo algorithm is applied to investigate the adsorption and the desorption rates until the surfaces reaction reaches the temperature-dependent equilibrium state. We find the reaction of methanol with hydrogen terminated Si(111) to be self-limited at temperatures over 400 K, since the methanol starts to react with itself.