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(a) The NV defect center is oriented along the  direction in the schematic diagram of the diamond lattice. (b) A typical room-temperature spectrum for the NV centers in a type-Ib diamond is displayed with the ZPLs indicated. (c) Results of the confocal-microscopy scans of the irradiated diamond sample before annealing (top) and after annealing (bottom) with the optical power, Pop = 1 mW. The spots correspond to the locations where the TEM beam was focused. The highest dose is on the right and the lowest dose is on the left on both figures. The fluorescence image before annealing is measured with no optical attenuator. The low-dose spots are not detected since theirfluorescence is low compared to the background. In the scanned fluorescence images with × 0.005 light attenuator afterannealing, the doses are 1.3, 2.6, 6.4× 1018; 1.3, 2.6, 6.4 × 1019; 1.3, 2.6, 6.4 × 1020; and 1.3, 2.6, 6.4 × 1021, respectively, left to right. (d) The photoluminescence spectra for each dose obtained at the same optical power and integration time. As the dosage increases, it is observed that the NV0 and NV− peaks also rise. The spectra for the low-dose spots are shown more clearly in the inset.
(a) The NV− and NV0 concentrations, as measured from fluorescence over 632–643 nm and 572–580 nm ranges, respectively, were normalized with respect to the maximum NV− concentration (Nmax.) at the highest dose. (b) The locally normalized NV− and NV0 concentrations are depicted as a function of depth. The depth profiles are calculated from the fluorescence spectra taken at different depths for the third highest-dose spot. (c) Electron trajectories were calculated with CASINO for 200 keV electrons incident on bulk diamond. Backscattered electrons are tracked in red. (d) The calculated electron-energy distribution.
(a) The energy level diagram for the NV− shows 2.87 GHz for the electron resonance frequency. (b) The wire is located close to the irradiated spots to apply the microwave signals and is parallel to the row of irradiated spots. (c) The CW ESR measurements are obtained using the same microwave power, Pmw = 25 dBm. The ESR frequency for the NV center (red line) increases as the dosage becomes higher and eventually the resonance disappears. (d) The ESR frequency shifts up as the dose increases. This shift can be explained by the distortion in the diamond lattice structure caused by the electron irradiation.
(a) The NV− concentration is plotted vs dose for doses where the ESR signal is visible. (b) The full-width half-maximum (FWHM) of the CW ESR linewidth is also depicted. (c) The standard deviation of the noise, σnoise, measured with microwave field detuned by a few linewidths from the ESR resonance frequency and the resulting SNR as a function of dose. (d) The calculated minimum detectable magnetic field with linewidth and SNR is minimized at the lowest dose.
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