“…In general, for a given sample and experimental procedure, the steady-state charge state efficiency is difficult to predict. Contributing factors include the concentration of substitutional nitrogen and other defects serving as charge donors or acceptors (Groot-Berning et al, 2014) and their microscopic distributions (Collins, 2002;Doi et al, 2016); the wavelength, intensity, and duty cycle of optical illumination (Aslam et al, 2013;Doi et al, 2016;Ji and Dutt, 2016;Manson and Harrison, 2005); the application of a bias voltage (Doi et al, 2014;Grotz et al, 2012;Kato et al, 2013;Schreyvogel et al, 2014); and, for near-surface NVs, the diamond surface termination (Chu et al, 2014;Cui and Hu, 2013;Fu et al, 2010;Groot-Berning et al, 2014;Hauf et al, 2011;Kageura et al, 2017;Newell et al, 2016;Osterkamp et al, 2015;Rondin et al, 2010;Santori et al, 2009;Yamano et al, 2017). The charge state efficiency is likely affected by the conditions of diamond growth, as well as the irradiation dose (Mita, 1996) (see Sec.…”