Authors: Jiashen Tang | Connor Roncaioli | Andrew M. Edmonds | Atli Davidsson | Connor Hart | Matthew Markham | Ronald L. Walsworth
Source: Frontiers in Quantum Science and Technology (article, 2025-12-09)
Field: Materials Science — Materials Chemistry

Characterization of low-nitrogen quantum diamond for pulsed magnetometry applications Ensembles of nitrogen-vacancy (NV) centers in diamond are versatile quantum sensors with broad applications in the physical and life sciences. The concentration of neutral substitutional nitrogen ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m1"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mo>[</mml:mo> <mml:mtext>N</mml:mtext> </mml:mrow> <mml:mrow> <mml:mtext>s</mml:mtext> </mml:mrow> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> ]) strongly influences NV electronic spin coherence times, sensitivity, and optimal sensing strategies. Diamonds with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m2"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mo>[</mml:mo> <mml:mtext>N</mml:mtext> </mml:mrow> <mml:mrow> <mml:mtext>s</mml:mtext> </mml:mrow> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> ] <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m3"> <mml:mrow> <mml:mo>∼</mml:mo> </mml:mrow> </mml:math> 1–10 ppm are a focus of recent material engineering efforts, with higher concentrations being favorable for continuous-wave optically detected magnetic resonance (CW-ODMR) and lower concentrations expected to benefit pulsed magnetometry techniques through extended NV spin coherence times and improved sensing duty cycles. In this work, we synthesize and characterize low- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m4"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mo>[</mml:mo> <mml:mtext>N</mml:mtext> </mml:mrow> <mml:mrow> <mml:mtext>s</mml:mtext> </mml:mrow> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> ] ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m5"> <mml:mrow> <mml:mo>∼</mml:mo> </mml:mrow> </mml:math> 0.8 ppm), NV-enriched diamond material, engineered through low-strain chemical vapor deposition (CVD) growth on high-quality substrates, 12 C isotopic purification, and controlled electron irradiation and annealing. Our results demonstrate good strain homogeneity in diamonds grown on CVD substrates and spin-bath-limited NV dephasing times. By measuring NV spin and charge properties across a wide range of optical NV excitation intensity, we provide direct comparisons of photon-shot-noise-limited magnetic field sensitivity between the current low- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m6"> <mml:mrow> <mml:mo stretchy="false">[</mml:mo> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mtext>N</mml:mtext> </mml:mrow> <mml:mrow> <mml:mtext>s</mml:mtext> </mml:mrow> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> <mml:mo stretchy="false">]</mml:mo> </mml:mrow> </mml:math> and previously studied higher- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m7"> <mml:mrow> <mml:mo stretchy="false">[</mml:mo> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mtext>N</mml:mtext> </mml:mrow> <mml:mrow> <mml:mtext>s</mml:mtext> </mml:mrow> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> <mml:mo stretchy="false">]</mml:mo> </mml:mrow> </mml:math> ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m8"> <mml:mrow> <mml:mo>∼</mml:mo> </mml:mrow> </mml:math> 14 ppm) NV-diamond sensors. We show that low- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m9"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mo>[</mml:mo> <mml:mtext>N</mml:mtext> </mml:mrow> <mml:mrow> <mml:mtext>s</mml:mtext> </mml:mrow> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> ] diamond can outperform higher- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m10"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mo>[</mml:mo> <mml:mtext>N</mml:mtext> </mml:mrow> <mml:mrow> <mml:mtext>s</mml:mtext> </mml:mrow> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> ] diamond at moderate and low optical NV excitation intensity. Our results provide practical benchmarks and guidance for selecting NV-diamond sensors tailored to specific experimental constraints and sensing requirements. Magnetometer ; Diamond ; Dephasing ; Coherence (philosophical gambling strategy) ; Magnetic field ; Chemical vapor deposition ; Electron paramagnetic resonance ; Nitrogen-vacancy center Diamond and Carbon-based Materials Research ; Mechanical and Optical Resonators ; High-pressure geophysics and materials