Regensburg 2013 – scientific programme
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O: Fachverband Oberflächenphysik
O 32: Metal Substrates I
O 32.5: Talk
Tuesday, March 12, 2013, 11:30–11:45, H42
Ab-initio modeling of electromechanical coupling at Si surfaces — •Sandra Hoppe1, Anja Michl1,2, Jörg Weissmüller2,3, and Stefan Müller1 — 1Institute of Advanced Ceramics, Hamburg University of Technology, Hamburg, Germany — 2Institute of Materials Research, Materials Mechanics, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany — 3Institute of Materials Physics and Technology, Hamburg University of Technology, Hamburg, Germany
Electrochemical experiments have revealed a linear dependence of the electrode potential E of metal surfaces on an applied strain e. This electromechanical coupling is characterized by the response parameter ∂ E/∂ e=const=: ς. As the potential of zero charge of an electrode surface in electrolyte is closely linked to its work function W in vacuum, ς is accessible via ab-initio calculations of ∂ W/∂ e . The response of the work function to strain has been investigated experimentally and in theory for various metals. In order to gain further insight into the influence of the electronic structure on the work function strain response, we have calculated coupling coefficients for silicon surfaces. Density functional theory with the HSE screened hybrid exchange-correlation functional was applied to obtain accurate Si band structures. In contrast to most metal surfaces, the magnitude of the response parameters does not increase with packing density for Si. This phenomenon is discussed regarding the strongly directional covalent semiconductor bonds and their distortion under applied strain.