Increasing the Magnetic Sensitivity of Ensembles of Nitrogen Vacancy Center Spins in Diamond for Wide Field Imaging

A magnetometer based on electron spin ensembles of nitrogen vacancy (NV) centers is a promising sensor for microscopic imaging of magnetic fields with high spatial and temporal resolution over a wide field of view. Enhancing sensitivity by increasing the density of NV centers while maintaining high spatial resolution is limited by inhomogeneous broadening inherent to spin ensembles. Starting with NV centers carefully engineered inside PECVD-grown diamond, we identify and quantify the factors that limit sensitivity in NV ensembles and we present our approach to mitigating their decohering effects. With the aid of dedicated sensing schemes we thus approach sensitivities of sub nanoTesla/√Hz in a 5x5x0.5 μm³ readout volume. This sensitivity and the magnetometer’s biocompatibility opens up exciting applications, e.g. probing biological action potentials of neurons plated on the diamond sensor.