Near-surface Nitrogen-vacancy Centers In Diamond Research Articles

Experimental Constraint on an Exotic Parity-Odd Spin- and Velocity-Dependent Interaction with a Single Electron Spin Quantum Sensor.

Improved laboratory limits on the exotic spin- and velocity-dependent interaction at the micrometer scale are established with a single electron spin quantum sensor. The single electron spin of a near-surface nitrogen-vacancy center in diamond is used as the quantum sensor, and a fused-silica half-sphere lens is taken as the source of the moving nucleons. The exotic interaction between the polarized electron and the moving nucleon source is explored by measuring the possible magnetic field sensed by the electron spin quantum sensor. Our experiment sets improved constraints on the exotic spin- and velocity-dependent interaction within the force range from 1.4 to 330 μm. The upper limit of the coupling g_{A}^{e}g_{V}^{N} at 200 μm is |g_{A}^{e}g_{V}^{N}|≤5.3×10^{-19}, significantly improving the current laboratory limit by more than 4 orders of magnitude.

Electric Noise Spectra of a Near-Surface Nitrogen-Vacancy Center in Diamond with a Protective Layer

Surface noise is a detrimental issue for sensing devices based on shallow nitrogen vacancy (NV) color center diamonds. A recent experiment indicates that electric field noise is significant compared to magnetic field noise. They also found that the electric field noise can be reduced with a protective surface layer, though the mechanism of noise reduction is not well understood. We examine the effect of a protective surface layer on the noise spectrum, which is caused by surface charge fluctuations. We use the fluctuation-dissipation theorem to calculate and analyze the noise spectrum for six different surface layer materials typically used for NV center diamond devices. We find that four parameters largely affect the noise spectrum: effective relaxation time, effective loss tangent, power law exponent of the noise spectrum, and layer thickness. Our results suggest that a surface covering layer is indeed useful for decreasing surface noise, but which material is most suitable depends on the device operational frequency range.

Searching for an exotic spin-dependent interaction with a single electron-spin quantum sensor

Searching for new particles beyond the standard model is crucial for understanding several fundamental conundrums in physics and astrophysics. Several hypothetical particles can mediate exotic spin-dependent interactions between ordinary fermions, which enable laboratory searches via the detection of the interactions. Most laboratory searches utilize a macroscopic source and detector, thus allowing the detection of interactions with submillimeter force range and above. It remains a challenge to detect the interactions at shorter force ranges. Here we propose and demonstrate that a near-surface nitrogen-vacancy center in diamond can be utilized as a quantum sensor to detect the monopole–dipole interaction between an electron spin and nucleons. Our result sets a constraint for the electron–nucleon coupling, g_{{mathrm{s}}}^{mathrm{N}}g_{mathrm{p}}^{mathrm{e}}, with the force range 0.1–23 μm. The obtained upper bound of the coupling at 20 μm is g_{{mathrm{s}}}^{mathrm{N}}g_{mathrm{p}}^{mathrm{e}} < 6.24 × 10−15.

Dynamic nuclear polarization enhanced magnetic field sensitivity and decoherence spectroscopy of an ensemble of near-surface nitrogen-vacancy centers in diamond

We perform pulsed optically detected electron spin resonance to measure the DC magnetic field sensitivity and electronic spin coherence time T2 of an ensemble of near-surface, high-density nitrogen-vacancy centers engineered to have a narrow magnetic resonance linewidth. Combining pulsed spectroscopy with dynamic nuclear polarization, we obtain the photon-shot-noise-limited DC magnetic sensitivity of 35 nT Hz−0.5. We find that T2 is controlled by instantaneous diffusion, enabling decoherence spectroscopy on residual nitrogen impurity spins in the diamond lattice and a quantitative determination of their density. The demonstrated high DC magnetic sensitivity and decoherence spectroscopy are expected to broaden the application range for two-dimensional magnetic imaging.

Nitrogen Terminated Diamond

Diamond surface termination with substitutional nitrogen is reported, leading to the formation of a stable surface which is essentially clear of sub-band surface states and has a positive electron affinity. This is predicted to be an ideal environment for near-surface nitrogen-vacancy centers in diamond and may enable magnetic and quantum sensing breakthroughs with these devices.

Reduced plasma-induced damage to near-surface nitrogen-vacancy centers in diamond.

Understanding plasma etch damage on near-surface nitrogen vacancy (NV) centers in diamond is essential for preserving NV emission in photonic structures and magnetometry systems. We have developed a methodology to compare the optical properties of ensemble NV centers initially 70 nm from the surface brought closer to the surface through etching with O2 plasmas in three different reactors. We employ a conventional reactive ion etcher, a barrel etcher, and a downstream etcher. We find that, irrespective of the etcher used, NV luminescence dims steadily as NVs are brought closer to the surface due to optical and surface effects. When NVs are less than 40 nm from the surface, differences in damage from the three different plasma processes affect the NV emission intensity in different ways. Diamond that is etched using the conventional etching method shows a greatly reduced NV luminescence, whereas NVs 15 nm from the surface still survive when the diamond is etched in the downstream reactor. As a result, downstream etching provides a possible alternative method for low damage etching of diamond for preservation of near surface NV properties.