Fluorine and oxygen terminated hexagonal diamond (100) surfaces for nitrogen-vacancy based quantum sensors

Chemical modification of hexagonal diamond surface is a new and important issue for the negatively charged nitrogen-vacancy (NV) center in quantum sensors. In this work, six types of terminated hexagonal diamond (100) surfaces for shallow NV centers are proposed, and structural and electronic properties are investigated by structure prediction method combined with first-principles calculation. In these structures, only fluorine and oxygen terminated surfaces (F-hex and & alpha;-O-hex) have positive electron affinity of 3.00 and 2.85 eV, respectively, no surface-related states and electron spin noise, indicating that the F-hex and & alpha;-O-hex surfaces could be a promising host of NV center. We make further inspections by placing an NV center-12 & ANGS; below the surfaces, and the results confirm that the surfaces have little effect on the defect states of NV center. Consequently, the F-hex and & alpha;-O-hex surfaces are prospective candidates for NV-based quantum sensors.