Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 36: Poster Session II (Metals; Nanostructures at surfaces; Surface or interface magnetism; Spin-Orbit Interaction at Surfaces; Electron and spin dynamics; Surface dynamics; Methods; Theory and computation of electronic structure)
O 36.85: Poster
Dienstag, 15. März 2011, 18:30–22:00, P4
Coordination defects at the Si/SiO2 interface investigated via ab initio g-tensor calculations — •Martin Rohrmüller, Uwe Gerstmann, and Wolf Gero Schmidt — Theoretische Physik, Universität Paderborn, 33098 Paderborn, Germany
The interface between silicon and SiO2 and its defects such as the Pb centers are technologically highly relevant and intensively investigated. Electron paramagnetic resonance (EPR) gives a magnetic fingerprint of the centers including the electronic g-tensor and the hyperfine splittings.
The so-called Pb1 center at the Si(100) surface is characterized by a strongly anisotropic g-tensor. Interestingly, the angular average coincides exactly with the EPR-resonance found in hydrogenated µ c-Si:H. In order to clarify if this coincidence is simply by chance, we calculate the elements of the electronic g-tensor for surface states and several oxidation stages from first principles, using the gauge-including projector augmented plane wave (GI-PAW) approach in the framework of density functional theory.
We find that (1) hydrogen adsorption at the Si(100) surface influences the magnetic signature of the material dramatically, whereby a large variety of g-tensors is obtained. (2) After oxidation, however, the g-tensors do not change considerably. The g-tensors resemble those of hydrogenated Si surfaces if the surface atoms are coordinated in the same way. This holds for all investigated surface states and the complete EPR fingerprint suggesting this technique to probe sensitively the crystalline part of the interface structures.