Nitrogen-vacancy (NV) centers in diamond are among the most promising solid-state qubit candidates, owing to their exceptionally long spin coherence times, efficient spin-photon coupling, room-temperature operation, and steadily advancing fabrication and integration techniques. Despite significant progress in the field, atomic-scale characterization and control of individual NV centers have remained elusive. In this work, we present a novel approach utilizing a conductive graphene capping layer to enable direct imaging and manipulation of $NV^{ -}$ defects via scanning tunneling microscopy (STM). By investigating over 40 individual $NV^{ -}$ centers, we identify their spectroscopic signatures and spatial configurations. Our dI/dV conductance spectra reveal the ground state approximately 300 meV below the Fermi level. Additionally, density-of-states mapping uncovers a two-lobed wavefunction aligned along the [111] crystallographic direction. Remarkably, we demonstrate the ability to manipulate the charge state of the NV centers from $NV^{ -}$ to $NV^{ 0}$ through STM tip-induced gating. This work represents a significant advancement in the atomic-scale understanding and engineering of NV centers, paving the way for future quantum device development.
Categories: quant-ph cond-mat.mes-hall cond-mat.mtrl-sci