Perfectly aligned shallow ensemble nitrogen-vacancy centers in (111) diamond

Abstract

We report the formation of perfectly aligned, high-density, shallow nitrogen vacancy (NV) centers on the Perfectly aligned shallow ensemble NV centers indicated a high Rabi contrast of approximately 30 % which is comparable to the values reported for a single NV center. Nanoscale NMR demonstrated surfacesensitive nuclear spin detection and provided a confirmation of the NV centers depth. Single NV center approximation indicated that the depth of the NV centers was approximately 9-10.7 nm from the surface with error of less than ±0.8 nm. Thus, a route for material control of shallow NV centers has been developed by step-flow growth using a CVD system. Our finding pioneers on the atomic level control of NV center alignment for large area quantum magnetometry. 6,7 . A fundamental limitation of an NV center based magnetometer is the material control required to confine the NV center in the vicinity (<10 nm) of the substrate surface with a high magnetic sensitivity.Previous studies that examined shallow NV centers focused on either a high-density ensemble for twodimensional large area imaging or a single NV center for high contrast and high coherent time to obtain a minimal detection volume using nanoscale NMR. However, it was found necessary to combine spatial localization of a NV centers with alignment, high density, and a long spin coherence time (T2) to obtain high magnetic sensitivity. The alignment of NV centers in an ensemble is the key to accomplish high contrast while maintaining high signal to noise ratio for high magnetic sensitivity with low accumulation time. In this regard, low energy ion implantation is the most common technique utilized for the production of NV centers in the vicinity of a surface 8 . However, this methodology suffers from large depth dispersion (>10 nm) of the NV centers due to ion straggling and channeling effects 9,10 . Additionally, high-density surface defects formed during implantation affect the spin coherence time and the ensembles show a random orientation with this technique 12,13,14 . Existing studies include reports of CVD growth that demonstrated a narrow distribution in the confinement of NV centers in the vicinity of a surface 11 and their atomic alignment on (100), (110), (113), and (111) substrates for the formation of thick diamond films 14,15,16,17,18,19,20 . Nearly all previous studies have focused on either low density NV centers (<10 13 cm -3 3 ) in the vicinity of a surface with no alignment 21,22,23 or the formation of NV ensembles with alignment in bulk.In this paper, the formation of a perfectly aligned high-density shallow NV center film for surfacesensitive detection of nuclear spin has been demonstrated. Results obtained from SIMS measurement combined with an effective depth obtained from nanoscale NMR measurement confirms presence of shallow NV center approximately 9-10.7 nm from surface with error of less than ±0.8 nm. The results of this study offer a path toward controlling the alignment of shallow NV center ensembles.In this study, NV-containing d...

Thermal Stability of Perfectly Aligned Nitrogen‐Vacancy Centers for High Sensitive Magnetometers

“…Hence the fluorescence from the NV centers along three directions which do not contribute to detect the magnetic field increases the background level, leading to the decrease in the contrast to ≈6% . On the other hand, an ensemble of the NV centers perfectly aligned along one direction can realize the maximum contrast of 30% . The fourfold increase in the contrast corresponds to a 16‐fold increase in the product of d NV and T 2 in Equation .…”

“…The spatial resolution of magnetic sensors that use NV centers can be arbitrarily determined by the volume of diamond layers containing NV centers. Nanoscale magnetic detection has been performed by measuring the object near the surface of the diamond with an isolated single NV center or a thin NV ensemble . On the other hand, the macro‐scale NV magnetometer (≈10 6 µm 3 ) has potential in biological/medical applications.…”

“…The fourfold increase in the contrast corresponds to a 16‐fold increase in the product of d NV and T 2 in Equation . The selective alignment of the N‐V axes has been realized by microwave plasma chemical vapor deposition (MPCVD) growth on (111) substrates . Therefore, macroscopic volume sensors with the selective NV alignment are expected to achieve highly sensitive magnetometers.…”

Wide-field diamond magnetometry with millihertz frequency resolution and nanotesla sensitivity

“…For an alternating current (AC) field sensing, the XY8based protocol with a coherence time (T 2 ) of the order of microseconds achieves a typical frequency resolution of around 10-100 kHz and a sensitivity of around 100 nT/Hz 1/2 using shallow NV center ensemble. 18,19 Recently reported phase sensitive measurement protocol 20-22 "Qdyne" drastically enhances the frequency resolution and the signal-to-noise ratio (SNR) without limitation of the coherence time imposed by the NV center.For wide-field sensing, it is necessary to use a cameratype sensor, such as a charge-coupled device (CCD), a) Author to whom correspondence should be addressed: hatano.m.ab@m.titech.ac.jp which requires a long readout sequence compared with a high-speed detector such as an avalanche photo diode implemented for Qdyne in Schmitt et al 20 . The detection time of an NV magnetometer is significantly shorter than the readout time; therefore, direct implementation of Qdyne leads to low sensitivity.…”

“…For an alternating current (AC) field sensing, the XY8based protocol with a coherence time (T 2 ) of the order of microseconds achieves a typical frequency resolution of around 10-100 kHz and a sensitivity of around 100 nT/Hz 1/2 using shallow NV center ensemble. 18,19 Recently reported phase sensitive measurement protocol [20][21][22] "Qdyne" drastically enhances the frequency resolution and the signal-to-noise ratio (SNR) without limitation of the coherence time imposed by the NV center.…”