Engineering preferentially-aligned nitrogen-vacancy centre ensembles in CVD grown diamond

Abstract

Here we report a method for improving the magnetic field sensitivity of an ensemble of Nitrogen-Vacancy (NV) centres in 12 C-enriched diamond aligned along the [111] crystal axis. The preferentially-aligned NV centres are fabricated by a Plasma Enhanced Chemical Vapour Deposition (PECVD) process and their concentration is quantitatively determined by analysing the confocal microscopy images. We further observe that annealing the samples at high temperature (1500 °C) in vacuum leads to a conversion of substitutional nitrogen into NV centres. This treatment also increases the coherence time of the NV centres electron spins up to 40 μs, which corresponds to enhancement of the sensitivity by a factor of three. However, this procedure also leads to a loss of the preferential alignment by 34%.

Benchmark for Synthesized Diamond Sensors Based on Isotopically Engineered Nitrogen‐Vacancy Spin Ensembles for Magnetometry Applications

“…[16,17] Compared to the lowenergy ion implantation technique, nitrogen incorporation (e.g., N doping) during diamond growth avoids the collateral damage of the crystal lattice, thus improving the spin environment of individual NV centers. Although some demonstration of enhanced magnetometry with preferentially aligned ensembles has been achieved, [18,19] the coherence time and the ensembles' density remain as critical limitations toward realistic applications. One of the primary reasons is the low N to NV creation efficiency in these samples.…”

“…However, this comes at the cost of lattice damages implying low coherence times and the loss of preferential orientation. [19,20] Another subtle approach is to tune the growth parameters in order to improve the NV incorporation during crystal growth. In this regard, a recent study shows the temperature dependence of NV incorporation in a ⟨113⟩-oriented diamond substrate while retaining preferential orientation.…”

Chemical vapour deposition diamond single crystals with nitrogen-vacancy centres: a review of material synthesis and technology for quantum sensing applications

“…Moreover, at low-power densities, it is difficult to obtain a high crystalline quality especially if one wants to grow the thick buffer layer (> 10 µm) [94,193] that is required to limit influence of the substrate on the overall luminescence. Nevertheless, deltadoped layers with highly confined NVs located in a 12 C layer have been produced (see figure 8(b-d)) [141] and have exhibited long coherence times of several hundreds of µs when the surface is sufficiently far away and/or free of defects [194]. This technique has also been coupled to local 12 C implantation in order to generate 3D profiles of NVs within the diamond sample [195].…”

“…Indeed, the optimal growth conditions window allowing keeping an α parameter lower than 1.5 strongly reduces when nitrogen concentration is increased in the feed gas. Nevertheless by using specific growth conditions in a low plasma density CVD, several tens of ppb of NV centres have recently been obtained with good alignment and moderate T2 times of the order of a few µs [194,255]. In particular it has been shown that lower growth temperatures (circa 800 °C rather than 1000 °C) are preferable to promote preferential alignment of those ensembles.…”

Photonic devices fabricated from (111)‐oriented single crystal diamond

“…Similar results were obtained previously for the NV centers in diamond that showed to preferentially incorporate into (111) grown diamonds. [25][26][27][28] The edges of both membranes have similar PL intensities since a (100)-oriented membrane has a (111) facet at the edge due to the three dimensional single crystal diamond growth. Both membranes do experience a drop-off in intensity toward the center of the membrane, this can be attributed to scattering enhancement at the edges and losses into bulk material.…”