Letter pubs.acs.org/NanoLett
Scalable Fabrication of High Purity Diamond Nanocrystals with Long-Spin-Coherence Nitrogen Vacancy Centers Matthew E. Trusheim,‡ Luozhou Li,§ Abdelghani Laraoui,∥ Edward H. Chen,‡ Hassaram Bakhru,⊥ Tim Schröder,‡ Ophir Gaathon,§,‡ Carlos A. Meriles,∥ and Dirk Englund*,‡ ‡
Department of Electrical Engineering and Computer Science, MIT, Cambridge, Massachusetts 02139, United States Department of Electrical Engineering, Columbia University, New York, New York 10027, United States ∥ Department of Physics, CUNY - City College of New York, New York, New York 10031, United States ⊥ College of Nanoscale Science and Engineering, University at Albany-State University of New York, Albany, New York 12203, United States §
ABSTRACT: The combination of long spin coherence time and nanoscale size has made nitrogen vacancy (NV) centers in nanodiamonds the subject of much interest for quantum information and sensing applications. However, currently available highpressure high-temperature (HPHT) nanodiamonds have a high concentration of paramagnetic impurities that limit their spin coherence time to the order of microseconds, less than 1% of that observed in bulk diamond. In this work, we use a porous metal mask and a reactive ion etching process to fabricate nanocrystals from highpurity chemical vapor deposition (CVD) diamond. We show that NV centers in these CVD nanodiamonds exhibit record-long spin coherence times in excess of 200 μs, enabling magnetic field sensitivities of 290 nT Hz−1/2 with the spatial resolution characteristic of a 50 nm diameter probe. KEYWORDS: Nanodiamond, nitrogen vacancy, long coherence, magnetometry, reactive ion etching
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coherently evolves. It has been shown that the spin coherence time of NV centers in bulk and nanocrystalline type Ib diamond is limited by the stochastic fluctuations of the magnetic field induced by the bath of paramagnetic impurities and surface defects with times T2* ∼ 250 ns and T2 ∼ 3 μs at 100 ppm.6,10 The growth of CVD diamond, however, can be controlled to limit nitrogen inclusion and sharply reduce the number of paramagnetic carbon-13 nuclear spins. The purity of this material has enabled a vast increase in NV coherence time beyond milliseconds11,12 with concomitant improvements in sensing applications.13−19 However, these improvements have not been accompanied by advances in the fabrication of nanocrystals where the best coherence lifetimes, attained via bottom-up CVD growth, do not exceed 10 μs.20 In this work, we fabricate nanocrystals directly from highpurity bulk CVD diamond with
