Integrated Microwave Coupling Device for Scanning Nitrogen-Vacancy Magnetometry

Scanning Nitrogen-Vacancy (NV) magnetometry has emerged in recent years as a leading technique for high-sensitivity nanoscale magnetic imaging. Efficient and robust delivery of microwave (MW) quantum control signals to NV centers in diamond scanning probes remains a significant challenge, in particular in cryogenic environments. Reducing the heat load and enabling a larger accessible sample space while achieving an optimized spin manipulation is crucial to widen the scope of applications.<br/><br/>Here, we present the design and the implementation of a new type of scanning NV magnetic imaging probe. The microwave coupling loop is directly integrated onto the scanning probe holding structure thereby eliminating the need for external MW delivery solutions. In this geometry, the NV sensor is in close proximity and at a constant distance to the coupling loop due to the rigid attachment. The microwave power required for spin manipulation is thereby decreased and made independent from the scanning probe position over the sample, two key aspects for imaging with good magnetic sensitivity. The device is created through a subtractive manufacturing process followed by the evaporation of a conductive material on its top side to form the MW stripline and loop. This original approach is simple, highly reproducible, and more importantly enables large-scale production as it does not rely on lithography. The characterization and the proof-of-principle scanning NV magnetometry experiment demonstrate that this new devices can outperform state-of-the-art MW delivery solutions, making it a compelling alternative. This holds for low-temperature experiments but is also anticipated to generally reduce the technical barriers for the broader adoption of NV magnetometry across a larger research community.<br/><br/>We acknowledge financial support through the NCCR QSIT (Grant No. 185902), the Swiss Nanoscience Institute, and through the Swiss NSF (Grant No. 188521).