Vacancy diffusion and nitrogen-vacancy center formation near the diamond surface

摘要

For the engineering of nitrogen-vacancy (NV) centers in diamond,vacancies have been introduced locally into a type Ib diamond (100-200 ppm nitrogen content) by implanting argon ions from a sub-500 nm focused beam. At an acceleration potential of 12 kV,different charge states (Ar ~(n+),n = {1,4,8,11}) result in kinetic energies of 12-132keV. NV-centers were formed by a subsequent annealing step. A wide range of fluences from around one ion to several hundred ions was implanted per spot. It was found that,on average,between 0.04 (12keV) and 0.79 (132 keV) NV-centers are created from the vacancies of a single implanted argon ion,depending on the ion energy,but not on the fluence. The different number of vacancies created at each energy alone cannot account for the difference in NV-center yield. However,the probability of a given vacancy to diffuse to the diamond surface during annealing,where it cannot contribute to NV-center formation,was simulated and can fully explain the NV-yield behavior. With this model,an upper bound of approximately 300 nm for the diffusion length of a single vacancy was found for an annealing temperature of 800°C.