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Diamond Materials

Diamond Materials for Quantum Application

23. September 2014: The DFG research group FOR 1493 “Diamond Materials and Quantum Applications” goes into its second funding period. FOR1493 is a national research consortium funded by the Deutsche Forsch-ungsgemeinschaft.

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ERC Advanced Grant

ERC

Toward Optimized Surface δ - Profiles of Nitrogen-Vacancy Centers

Toward Optimized Surface δ – Profiles of Nitrogen-Vacancy Centers Activated by Helium Irradiation in Diamond

The negatively-charged nitrogen-vacancy (NV) center in diamond has been shown recently as an excellent sensor for external spins. Nevertheless, their optimum engineering in the near-surface region still requires quantitative knowledge in regard to their activation by vacancy capture during thermal annealing. To this aim, we report on the depth profiles of near-surface helium-induced NV centers (and related helium defects) by step-etching with nanometer resolution. This provides insights into the efficiency of vacancy diffusion and recombination paths concurrent to the formation of NV centers. It was found that the range of efficient formation of NV centers is limited only to approximately 10 to 15nm (radius) around the initial ion track of irradiating helium atoms. Using this information we demonstrate the fabrication of nanometric-thin (δ) profiles of NV centers for sensing external spins at the diamond surface based on a three-step approach, which comprises (i) nitrogen-doped epitaxial CVD diamond overgrowth, (ii) activation of NV centers by low-energy helium irradiation and thermal annealing, and (iii) controlled layer thinning by low-damage plasma etching. Spin coherence times (Hahn echo) ranging up to 50 μs are demonstrated at depths of less than 5nm in material with 1.1% of 13 C (depth estimated by spin relaxation (T 1) measurements). At the end, the limits of the helium irradiation technique at high ion fluences are also experimentally investigated.

Reference:
Nano Letters, 2016, 16 (4), pp 2228–2233
Felipe Fávaro de Oliveira, S. Ali Momenzadeh, Denis Antonov, Jochen Scharpf, Christian Osterkamp, Boris Naydenov, Fedor Jelezko, Andrej Denisenko, and Jörg Wrachtrup
DOI: 10.1021/acs.nanolett.5b04511