Enhanced metrology using preferential orientation of nitrogen-vacancy centers in diamond

We demonstrate preferential orientation of nitrogen-vacancy (NV) color centers along two of four possible crystallographic axes in diamonds grown by chemical vapor deposition on the $\left\{100\right\}$ face. We identify the relevant growth regime and present a possible explanation of this effect. We show that preferential orientation provides increased optical readout contrast for NV multispin measurements, including enhanced ac magnetic-field sensitivity, thus providing an important step towards high-fidelity multispin-qubit quantum information processing, sensing, and metrology.

Figure 1

Four possible orientations of nitrogen-vacancy (NV) color centers in diamond. Carbon atoms are depicted in black, nitrogen (N) atoms in blue, and vacancies (V) in white. NV electronic spin is indicated by red arrows.

Figure 2

ESR spectra with static magnetic field ($B_0=80$ G) along each of four diamond crystallographic axes for (a) sample A, which exhibits no preferential NV orientation, and (b) sample B, which exhibits a high level ($\sim$94$\%$) of preferential NV orientation. (c) Atomic-level model of NV incorporation in $\left(100\right)$ step-flow growth, indicating mechanism for preferential NV occupation of only two orientations. (d) Diagram of $\left\{100\right\}$ step-flow growth surface and fluorescence striations. (e) Confocal cross-section of a sample which exhibits fluorescence striations characteristic of $\left\{100\right\}$ step-flow growth. Microscope images of the surface morphologies of (f) sample A (scanning confocal) and (g) sample B (differential interference contrast).

Figure 3

Comparison for NV nonoriented sample A and preferentially oriented sample B of (a) NV spin coherence decay measured using a (b) Hahn echo pulse sequence (timing of ac magnetic field to be measured is shown in green), (c) NV magnetometry signal (i.e., fluorescence contrast) of an ac magnetic field of frequency $f_{\text{ac}}=3.08$ kHz as a function of magnetic-field amplitude acquired using the same method as in Ref. 10, and (d) ac magnetic-field sensitivity as a function of measurement time. Spin-state-dependent optical readout contrast from sample B is $\gtrsim$2 times larger than from sample A, leading to similarly improved magnetic-field sensitivity.