Enhancing nitrogen-vacancy activation in diamond with phosphorus co-implantation*

Diamond is a promising material for the creation of stable nitrogen-vacancy (NV) centers for quantum sensing. The sensitivity of an NV-ensemble sensor depends on the number of activated NVs in the substrate and their proximity to the sample under test.  However, their activation rate close to the diamond surface is drastically reduced from ~30% in the bulk to <1% at 10nm. The low activation rate near the surface hinders the use of NVs as a nano-scale material sensor. The addition of phosphorus (P) to nitrogen (N)-doped diamond has been shown to increase the creation yield percent of NV per implanted N, but specific combinations must be optimized.

We present a systematic co-implantation study of P and N near the surface of diamond to increase activation of NVs while maintaining ideal spin properties. We first implant the diamond with P in 100μm² patches (1–2700ppm), activating the P with a UHV high temperature anneal, followed by a blanket implant of N (20ppb or 10ppm). We compare photoluminescence (PL) intensity and spectra for each treatment. Then we characterize spin properties by measuring PL spin contrast, T2*, T2, and T1.  Initial results show that co-implantation of P at 100ppm can improve NV activation by nearly a factor of 2x with spin properties soon to be determined.