Quantum diamond spectrometer for nanoscale NMR and ESR spectroscopy

Nitrogen-vacancy (NV) quantum defects in diamond are sensitive detectors of magnetic fields. Due to their atomic size and optical readout capability, they have been used for magnetic resonance spectroscopy of nanoscale samples on diamond surfaces. Here we present a protocol for fabricating NV-diamond chips and for constructing and operating a simple, low-cost quantum diamond spectrometer for performing nuclear magnetic resonance (NMR) and electron spin resonance (ESR) spectroscopy in nanoscale volumes. The instrument is based on a commercially-available diamond chip, with an ion-implanted NV-ensemble at a depth of ~ 10 nm below the diamond surface. The spectrometer operates at low magnetic fields (~ 300 G) and requires standard optical and microwave components for NV spin preparation, manipulation and readout. We demonstrate the utility of this device for nanoscale proton and fluorine NMR spectroscopy, as well as for the detection of transition metals via ESR noise spectroscopy. We estimate that the full protocol requires 2-3 months to implement, depending on the availability of equipment, diamond substrates, and user experience.