Extending spin dephasing time of perfectly aligned Nitrogen-Vacancy centers by mitigating stress distribution on highly misoriented chemical-vapor-deposition diamond

TL;DR

This paper presents a method to mitigate stress in CVD diamond films, significantly extending the spin dephasing time of NV centers, thereby improving the sensitivity of quantum sensors.

Contribution

The study introduces a technique to reduce stress distribution in CVD diamonds, enhancing NV center coherence times for better quantum sensing performance.

Findings

T2* approaches the limit set by spin bath interactions with increased misorientation.

Stress inhomogeneity decreases with higher misorientation angles.

Reduced dislocation density correlates with improved NV coherence.

Abstract

Extending the spin-dephasing time (T2*) of perfectly aligned nitrogen-vacancy (NV) centers in large-volume chemical vapor deposition (CVD) diamonds leads to enhanced DC magnetic sensitivity. However, T2* of the NV centers is significantly reduced by the stress distribution in the diamond film as its thickness increases. To overcome this issue, we developed a method to mitigate the stress distribution in the CVD diamond films, leading to a T2* extension of the ensemble NV centers. CVD diamond films of approximately 50 \mu m thickness with perfectly aligned NV centers were formed on (111) diamond substrates with misorientation angles of 2.0, 3.7, 5.0, and 10{\deg}. We found that T2* of the ensemble of NV centers increased to approach the value limited only by the electron and nuclear spin bath with increasing the misorientation angle. Microscopic stress measurements revealed that the stress distribution was highly inhomogeneous along the depth direction in the CVD diamond film at low misorientation angles, whereas the inhomogeneity was largely suppressed on highly misoriented substrates. The reduced stress distribution possibly originates from the reduction of the dislocation density in the CVD diamond. This study provides an important method for synthesizing high-quality diamond materials for use in highly sensitive quantum sensors.