Alignment of the diamond nitrogen vacancy center by strain engineering

Abstract

The nitrogen vacancy (NV) center in diamond is a sensitive probe of magnetic field and a promising qubit candidate for quantum information processing. The performance of many NV-based devices improves by aligning the NV(s) parallel to a single crystallographic direction. Using ab initio theoretical techniques, we show that NV orientation can be controlled by high-temperature annealing in the presence of strain under currently accessible experimental conditions. We find that (89 ± 7)% of NVs align along the [111] crystallographic direction under 2% compressive biaxial strain (perpendicular to [111]) and an annealing temperature of 970• C.The prospect of nanoscale sensing at ambient conditions has spurred renewed interest in the mature field of point-defect physics. Studying point-defect physics using ab initio computational techniques expands our understanding of important crystal defects and widens the scope of applicability for defect based devices. In this work, we show that the orientation of the nitrogenvacancy (NV) center in diamond can be controlled by annealing in the presence of strain.The diamond NV center is a technologically-relevant and well-studied defect consisting of a substitutional nitrogen and nearest-neighbor vacancy (Fig. 1).1-3 The center's electron spin-triplet ground state has an unusually long spin coherence time, exceeding 1 ms at room temperature.4 This long coherence time, coupled with the ability to perform optically detected magnetic resonance, enables the NV center to be used as a sensitive probe of temperature, 5 electric field, 6 magnetic field, 7-10 strain, 11and pressure. 12 The NV center is also a promising qubit candidate for quantum information applications. 13-15Many NV-based devices would benefit from simultaneous control over the NV position and orientation in the host diamond. Due to the tetrahedral coordination of the diamond lattice, the NV has four possible orientations, two of which are shown in Fig. 1. Control over orientation increases NV homogeneity and improves the performance of sensors based on ensembles. In magnetic sensing for example, alignment inhomogeneity increases noise because only the magnetic field projection on the NV symmetry axis is measured.9,16 Similarly, quantum information applications typically require qubits with identical properties, including alignment, to facilitate qubit coupling and entanglement generation.17-19 Finally, both sensing and quantum information may benefit from coupling the NV to an optical resonator, where NV dipole alignment to the resonant mode polarization is critical. 20-22Current techniques to create NVs provide control over either NV position or orientation, but not both simultaneously. In chemical vapor deposition grown diamond, NV defects may align to a preferential direction during growth, over spatial location. Conversely, implantation and annealing positions NVs to nanoscale accuracy, 25 but leaves them randomly oriented. Our method aligns pre-existing NV centers through strain engineering, thus enabling simulta...

Window into NV center kinetics via repeated annealing and spatial tracking of thousands of individual NV centers

“…The maximum fraction of orientations we observe is 0.36, during anneal 16, from which we estimate 54% of NV centers have undergone an orientation change (since we are unable to observe changes within the same orientation set). We can estimate the orientation-change barrier E b using orientation change rate R = νexp(−E b /kT ), with ν = 3 × 10 13 s −1 [43], to find E b = 5.1 eV. This value is close to the theoretical value of 4.85 eV [42] determined by density functional theory calculations.…”

Photothermal effects during nanodiamond synthesis from a carbon aerogel in a laser-heated diamond anvil cell

“…Interestingly, this also implies that varying the pressure could provide the ability to control defect formation. Finally, while there have been recent reports on strain-alignment of defects, we do not anticipate any preferential alignment due to the near-hydrostatic nature of the argon pressure medium [54].…”

Wide-field strain imaging with preferentially aligned nitrogen-vacancy centers in polycrystalline diamond

“…This effect persists independent of the direction of the applied permanent magnetic field (supplemental material), and across grains in the PCD. Preferential orientation of NVs through engineered growth has been theoretically predicted [16,17] and observed previously in single crystal diamond with controlled growth along {110} [18,19], {111} [20,21] and {113} [22]. These results indicate that preferential alignment occurs naturally in PCD, possibly due to predominant {110} and {111} grain textures.…”