Co-engineered diamond NV centers via MPCVD for non-invasive quantum sensing in integrated circuits

The nitrogen-vacancy (NV) center in diamond is a point defect formed by a substitutional nitrogen atom adjacent to a carbon vacancy. Owing to its exceptional fluorescence properties and long quantum coherence, the NV center has broad applications in quantum computing, quantum sensing, and magnetic field imaging. This study focuses on the magnetic field sensing capabilities of NV centers, with performance critically dependent on the NV concentrations and coherence time. High-performance NV center diamond samples were synthesized using microwave plasma chemical vapor deposition (MPCVD) with controlled nitrogen doping, followed by electron irradiation and high-temperature annealing. We obtained diamond samples with high NV concentrations and a coherence time of T2* = 0.48 μs. These diamonds were processed into micrometer-sized crystals via laser cutting and polishing, then integrated into an optical fiber-based probe for magnetic field detection. The sensor’s performance was first characterized independently, with a magnetic sensitivity of 5.77 nT/Hz and a magnetic resolution of 0.1 G@4715 G. Subsequently, two-dimensional magnetic field imaging experiments were performed on chip surfaces, demonstrating the probe’s capability for precise mapping of local magnetic fields.