Shallow silicon vacancy centers with lifetime-limited optical linewidths in diamond nanostructures

I. SIV -YIELD ESTIMATIONWe predicted our target implantation density of 6 × 10 9 ions/cm 2 by using yield estimates from previous samples, where we observed a Si → SiV -conversion efficiency of ∼ 0.03 after implantation with 28 Si ions at a fluence of 1.5 × 10 11 ions/cm 2 and 80 keV, the first annealing procedure and parabolic reflector fabrication and of ∼ 0.18 after the second anneal.After the first annealing and after parabolic reflector (PR) fabrication, we could still find single SiV -centers in our PRs even at this high implantation fluence, which was not the case after the second anneal.Based on simple back-of-the envelope calculations, we estimated that a fluence of 1 × 10 10 ions/cm 2 would yield single SiV -centers in PRs with diameters around 300 nm in combination with two annealing procedures.We then opted for the slightly lower fluence to facilitate subsequent characterization.The reason for the switch from 28 Si to 29 Si was based on technicalities with the implantation provider.If a single stage implanter is used, it is possible that 28 N 2 is implanted alongside 28 Si, leading to unwanted contamination of the sample and an increased yield of NV centers.We do not expect an impact on optical coherence based on this change.