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

TL;DR

This study systematically investigates how to optimize nitrogen-vacancy centers in CVD diamond for sensing, focusing on nitrogen concentration, irradiation conditions, and resulting spin coherence times to enhance quantum sensing performance.

Contribution

It provides a comprehensive methodology for controlling NV center formation and properties in CVD diamond, optimizing conditions for improved quantum sensing applications.

Findings

Achieved spin coherence times up to 549 μs.

Identified optimal irradiation conditions for maximum NV concentration.

Demonstrated control over NV charge states and defect formation.

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 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 T$_2$ ranging from 45.5 to 549 $\mu$s 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.