Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 17: Semiconductor Substrates
O 17.1: Vortrag
Montag, 31. März 2014, 16:00–16:15, PHY C 213
Structural sensitivity of the electromechanical coupling at Si surfaces — •Sandra Hoppe1, Anja Michl1,2, Jörg Weissmüller2,3, and Stefan Müller1 — 1Institute of Advanced Ceramics, Hamburg University of Technology, Germany — 2Institute of Materials Research, Materials Mechanics, Helmholtz-Zentrum Geesthacht, Germany — 3Institute of Materials Physics and Technology, Hamburg University of Technology, Germany
Electromechanical coupling describes a relation between a material's mechanical and electronic properties. It has been found for various metal surfaces that an applied strain leads to a change in the work function. While this phenomenon has been studied for silicon nanowires and silicene, surprisingly, no results are available for clean silicon surfaces. We investigated the electromechanical coupling at the silicon (100) and (111) surfaces via density functional theory by calculating the response of the ionization potential and the electron affinity to different types of strain. The highest occupied and the lowest unoccupied molecular orbital (HOMO and LUMO) were obtained from the surface states within the surface band gap. We find large negative response parameters and a high sensitivity of the strain response to surface relaxations. This can be attributed to the directional bonds in covalent semiconductors and discussed in terms of volume and surface contributions to the response of the surface dipole potential and the electronic structure to strain. While we find a considerable volume influence on the dipole potential, the response of HOMO and LUMO seems to be dominated by the local reconstruction geometry.