On the efficiency of combined ion implantation for the creation of near-surface nitrogen-vacancy centers in diamond

The efficiency of co-implantation of different ion species to generate near-surface nitrogen-vacancy (NV) centers in diamond is analyzed by comparing the areal densities of NV centers corresponding to various experimental conditions. In particular, the effect of helium (6 keV He-2(+)) and carbon (10 keV C+) co-implantation within a wide range of ion fluences are studied. The total density of NV centers by co-implantation are shown to be basically a sum of the nitrogen-induced NV centers and those activated from residual nitrogen impurities present in the substrate (approximately 1 ppb) by the excess of vacancies at the carbon-and helium-induced ion tracks. Such low efficiency of the co-implantation events is discussed considering the model of local clusters of vacancies at each implantation-induced ion track. This is also experimentally supported by the presence of a photoluminescence (PL) background related to radiation-induced defects measured within all implanted areas with high carbon and helium ion fluences. Further limits set by the annealing temperature are also discussed. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim