Ultrahigh concentration NV- center embedded in the CVD epi-diamond layer near the interface to a HPHT diamond substrate

Abstract The negatively Nitrogen Vacancy (NV - ) center ensemble in as-grown Chemical Vapor Deposition (CVD) diamond is a promising candidate for quantum sensing due to its long coherence time and excellent optical properties. However, achieving a high concentration of NV - center in as-grown CVD diamond remains a critical challenge, which constrains the performance of NV - based sensors. In this study, we observe that NV - center formation efficiency is significantly enhanced during the initial growth phase, with the coherence time T 2 * of NV - centers reaching 1.1 μs. These findings highlight the realization of high-concentration NV - centers in as-grown diamonds, enhancing their potential for high-performance magnetometers and quantum sensing technologies.