Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 46: Surface magnetism I (jointly with MA)

O 46.5: Vortrag

Mittwoch, 16. März 2011, 12:15–12:30, CHE 184

Magnetic signature of surface defects at nanodiamonds — •Nora Jenny Vollmers, Uwe Gerstmann, and Wolf Gero Schmidt — Theoretische Physik, Universität Paderborn

The n-type doping of diamond has been a long-standing issue, which recently gained attention in the context of nanodiamonds. Attempts of doping with nitrogen failed to result in the Electron paramagnetic Resonance (EPR) fingerprints expected from bulk material. Instead, the nanodiamond signals show a much larger deviation from the free-electron g-value and are believed to be related to intrinsic, carbon inherited defects. However, the absence of the bulk-like EPR spectra does not mean that nitrogen is not incorporated at all. The N atoms could be built in predominantly at or at least close to the surfaces yielding EPR spectra, very different from those measured in the bulk.

In this work, we elucidate the situation by investigating the magnetic signature of paramagnetic defects in the nanodiamonds. We use the gauge-including projector augmented plane wave (GI-PAW) approach [1, 2] to calculate the hyperfine splittings and the elements of the electronic g-tensor. Taking the C(100) surface as a first model system, a possible contribution of nitrogen is discussed by comparing EPR parameters for different N incorporation depths: Incorporated directly at the surface, N gives rise to surface states similar to intrinsic carbon dangling bond-like states. Otherwise N is able to introduce surface conductivity as demonstrated by calculated effective mass tensors.

[1] Ch.J. Pickard, F. Mauri, Phys. Rev. Lett. 88, 086403 (2002).

[2] U. Gerstmann et al., phys. stat. sol. (c) 7, 157 (2010).