Investigation of NV centers charge states in CVD diamond layers doped by nitrogen and phosphorous

Highlights: • Nitrogen-vacancy color centers in diamond are promising for spin-based sensors. • If state readout of NV center is performed optically, only the NV- state is used. • NV- state is enhanced by n-type doping and impeded by photoionization. • Nitrogen doping itself enhances the NV- state, but decreases the coherence times. • Strong phosphorus doping enhances the NV- state and suppresses its photoionization. Nitrogen-vacancy color centers in CVD diamond are promising candidates for many quantum applications. In particular, they can be used as sensors for electric and magnetic fields with high sensitivity and nanometer scale spatial resolution. When state readout is performed optically, only the NV⁻ charge state can be used, therefore, it is important to have the maximum concentration of NV centers in the NV⁻ state. In this work, the effect of combined nitrogen-phosphorus doping of diamond on the balance of charge states of NV centers is studied in a wide range of dopant concentrations and at different power of the laser used for photoluminescence excitation. It is shown that the use of a combination of doping with nitrogen and phosphorus makes it possible not only to ensure that NV centers in diamond predominantly exist in the NV⁻ state, but also to stabilize the NV⁻ state under conditions of high power of excitation laser. Cooling with liquid nitrogen allows to further increase the fraction of the NV⁻ state. The obtained results may be applicable for a number of practical tasks, such as optimization of the sensitivity of magnetometers.