Quantitative nanoscale MRI with a wide field of view

Abstract

Novel magnetic sensing modalities using quantum sensors or nanoscale probes have drastically improved the sensitivity and hence spatial resolution of nuclear magnetic resonance imaging (MRI) down to the nanoscale. Recent demonstrations of nuclear magnetic resonance (NMR) with paramagnetic colour centres include single molecule sensitivity, and sub-part-per-million spectral resolution. Mostly, these results have been obtained using well-characterised single sensors, which only permit extended imaging by scanning-probe microscopy. Here, we enhance multiplexed MRI with a thin layer of ensemble spin sensors in an inhomogeneous control field by optimal control spin manipulation to improve ensemble sensitivity and field of view (FOV). We demonstrate MRI of fluorine in patterned thin films only 1.2 nm in thickness, corresponding to a net moment of 120 nuclear spins per sensor spin. With the aid of the NMR signal, we reconstruct the nanoscale depth distribution of the sensor spins within the substrate. In addition, we exploit inhomogeneous ensemble control to squeeze the point spread function of the imager to about 100 nm and show that localisation of a point-like NMR signal within 40 nm is feasible. These results pave the way to quantitive NMR ensemble sensing and magnetic resonance microscopy with a resolution of few ten nanometers.