Increasing the coherence time of single electron spins in diamond by high temperature annealing

Negatively charged nitrogen-vacancy (NV(-)) centers in diamond produced by ion implantation often show properties different from NVs created during the crystal growth. We observe that NVs created from nitrogen ion implantation at 30-300 keV show much shorter electron spin coherence time T(2) as compared to the natural NVs and about 20% of them show switching from NV-to NV(0). We show that annealing the diamond at T=1200 degrees C substantially increases T2 and at the same time the fraction of NVs converting from NV-to NV(0) is greatly reduced. (C) 2010 American Institute of Physics. [doi:10.1063/1.3527975]