Regensburg 2025 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 29: Poster II

HL 29.40: Poster

Tuesday, March 18, 2025, 18:00–20:00, P1

Effect of TiO₂ thin films on the charge state of shallow NV centers in diamond. — •Arthur Witte, Tobias Lühmann, Peter Schlupp, Dominic Reinhardt, Holger von Wenckstern, and Marius Grundmann — Universität Leipzig, Felix-Bloch Institute for Solid State Physics, Germany

The nitrogen vacancy (NV) center is a color center in diamond. In its negative charge state, it has a relatively long spin coherence time at room temperature and a spin-dependent photoluminescence that enables optical spin polarization. Because of these properties, the NV center was proposed as a platform for room-temperature quantum computing. For this application the NV centers must be located close to the diamond surface. This can present new challenges due to surface effects resulting in, e.g. charge state instabilities of the shallow NV centers. Various surface treatments can be used to mitigate these effects, such as thermal oxidation, plasma surface treatments or the deposition of a thin passivation layer on the diamond surface.

We present a titanium dioxide thin film as the passivation layer. Titanium dioxide is a wide-bandgap semiconductor with a high refractive index of 2.5. In a first step, we investigate the growth of titanium dioxide layers by pulsed laser deposition and long-throw sputtering under different conditions. We then study the effect of optimized titanium dioxide layers on the luminescence properties of NV centers at implantation depths between 7 nm and 67 nm. Through spectroscopic analysis, we observe a significant increase in charge stabilization of shallow NV centers.

Keywords: NV center; diamond; titanium oxide; charge state