Creation of nitrogen-vacancy centers in chemical vapor deposition diamond for sensing applications

Abstract

The nitrogen-vacancy (NV) center in diamond is a promising quantum system for magnetometry applications exhibiting optical readout of minute energy shifts in its spin sub-levels. Key material requirements for NV ensembles are a high NV- concentration, a long spin coherence time and a stable charge state. However, these are interdependent and can be difficult to optimize during diamond growth and subsequent NV creation. In this work, we systematically investigate the NV center formation and properties in bulk chemical vapor deposition (CVD) diamond. The nitrogen flow during growth is varied by over 4 orders of magnitude, resulting in a broad range of single substitutional nitrogen concentrations of 0.2-20~parts per million. For a fixed nitrogen concentration, we optimize electron-irradiation fluences with two different accelerated electron energies, and we study defect formation via optical characterizations. We discuss a general approach to determine the optimal irradiation conditions, for which an enhanced NV concentration and an optimum of NV charge states can both be satisfied. We achieve spin-spin coherence times T2 ranging from 45.5 to 549 μs for CVD diamonds containing 168 to 1~parts per billion NV- centers, respectively. This study shows a pathway to engineer properties of NV-doped CVD diamonds for improved sensitivity.

Manipulation of the In Situ Nitrogen‐Vacancy Doping Efficiency in CVD‐Grown Diamond

“…Whereas, literature in general states theoretical as well as experimental incorporation probabilities of below 0.5%. [ 18,38,39 ]…”

“…a) UV‐vis spectra depicting the variation in concentration of the corresponding samples to b) NV‐to‐ ratio implying the incorporation efficiency plotted as a function of the electric‐field strength at the sample position including a range of standard literature values. [ 18,38,39 ] …”

“…Further information on the quantification method is described elsewhere. [ 38 ] The center concentration was calculated via the absorption coefficient at around 270 nm measured through a 2 mm pinhole across the central part of the diamond sample by a Perkin Elmer Lambda950 UV‐vis spectrometer. [ 42 ]…”

Impact of Helium Ion Implantation Dose and Annealing on Dense Near-Surface Layers of NV Centers

“…Nitrogen ion implantation is used in crystals with low initial nitrogen concentration [11][12][13][14][15], and the advantage of this method is the control of nitrogen distribution within the diamond; the disadvantage is the relatively high damage to the crystal during the implantation, thus introducing undesirable defects and impurities that might create charge traps, paramagnetic centers, and vacancy chains, leading to increased spectral diffusion and degraded spin coherence properties [16][17][18]. In addition, this method suffers from electron donor deficit leading to lower NV 0 to NV − charge-state conversion efficiency [19], since it is usually applied to diamonds with a low initial concentration of nitrogen. Another widely used method is electron irradiation [20][21][22][23], which creates vacancies in crystals with already sufficient nitrogen concentration.…”

Impact of helium ion implantation dose and annealing on dense near-surface layers of NV centers

“…Nitrogen ion implantation is used in crystals with low initial nitrogen concentration [10][11][12][13][14], and the advantage of this method is the control of nitrogen distribution within the diamond, but the disadvantage is the relatively high damage done to the crystal during the implantation, thus introducing undesirable defects and impurities that might create charge traps, paramagnetic centers and vacancy chains, leading to increased spectral diffusion and degraded spin coherence properties [15][16][17]. In addition, this method, since it is usually applied to diamonds with low initial concentration of nitrogen, suffers from electron donor deficit leading to lower NV 0 to NV − charge-state conversion efficiency [18]. Another widely used method is electron irradiation [19][20][21][22], which creates va- * Electronic address: andris.berzins@lu.lv cancies in crystals with already sufficient nitrogen concentration.…”