Scanning Tunneling Microscopy and Spectroscopy of Diamond with Nitrogen-Vacancy Centers

Spin qubits using nitrogen-vacancy (NV) centers in diamond are leading candidates for quantum information applications as a result of their millisecond spin coherence times, optical addressability, and room-temperature operation. While very extensive work has been undertaken in characterizing and applying NV centers, an atomic-scale picture of the defects' electronic states has remained elusive. Scanning tunneling microscopy (STM) would typically be an ideal technique for such atomic-scale visualization. However, thus far, STM has been unable to probe these defects due to the highly insulating nature of the diamond host crystal. In this work, we pursue a novel approach to visualizing NVs using STM. We image the atomic-scale topographic features of our samples, identify unique subsurface defects, and characterize their electronic states using scanning tunneling spectroscopy. Finally, we test the manipulability of these defects in our in-situ STM set-up using laser illumination and the STM tip.