Figure 1

(a) Photoluminescence intensity map of the diamond surface. Shallowest 0.4 keV defects are visible at the very top. The excitation wavelength was 532 nm and the detection bandwidth was 630–800 nm for all experiments except (c) and (d). (b) Close-up of an implantation spot at $5.0\mathrm{keV}$ [white square in (a)]. Some single NV centers are encircled. (c) Luminescence intensity due to NV${}^{-}$ (full circles) and NV${}^0$ (empty circles) as a function of ion energy at a fluence of $8\times {10}^{11}{\mathrm{cm}}^{-2}$, measured using two pairs of filters and corrected for spectral overlap.[12, 23] (d) Luminescence intensity as a function of ion fluence at an energy of $5\mathrm{keV}$.Reuse & Permissions

Figure 2

Electron spin resonance measurements on shallow NV defect spins. (a) Representative spectra (out of $>$30 total) showing increased line broadening at shallow depths. Black dots are experimental points and red solid lines are Lorentzian fits. Implanted ${}^{15}$NV (nuclear spin $I=1/2$) are distinguished from native ${}^{14}$NV ($I=1$, $99.6\%$ natural abundance) by the different hyperfine manifold. The magnetic bias field is about 20 gauss. (b) ESR linewidth $\Delta \omega /2\pi$ (half width at half height) plotted against surface proximity $d$. Black dots are experimental values obtained from many separately fitted curves, such as the ones shown in (a). Error bars denote standard error. The solid red line is a fit to the black dots based on Eq. (2) including motional averaging. The dashed red line is the static second moment [Eq. (1)] shown for comparison. The linewidth of reference ${}^{14}$NV is also shown. (c) Spectra of a 1.1 nm defect at zero field (left) and at 3.5 gauss bias field (right) rule out the presence of significant surface strain or charge (see text).Reuse & Permissions

Figure 3

Sketch of a nitrogen vacancy defect spin near a paramagnetic surface impurity layer, as described in the text. $d$ and $\theta$ denote distance and orientation, respectively, of the defect spin to the interface plane, and quantization is along the NV axis. A potential target spin, representative for sensing applications, is also shown.Reuse & Permissions

Figure 4

Hahn echo decay of a 1.1 nm ${}^{15}$NV center and, for comparison, for a 7.7 nm ${}^{15}$NV and a native ${}^{14}$NV defect. Black curves are experimental data and red lines are fits. The fit function is given in Ref. 23.Reuse & Permissions