Room-temperature formation and identification of the three silicon vacancy charge states in CVD diamond

The electrical charge state of point defects hosted in diamond has emerged as a promising resource for improved quantum sensing and information processing

schemes. The silicon-vacancy center in diamond possesses three stable charge states: SiV0, SiV- and SiV2-, but only SiV- exhibits detectable photoluminescence at room temperature. Optical illumination of the diamond can change the charge state by photoionisation or recombination of SiV defects, or indirectly, via photoionisation of ancilla defects (NV centers or P1 centers) and subsequent charge carrier capture by SiV. Here we show that with careful selection of the optical illumination and readout parameters, all three charge states can be prepared and identified at room temperature. We use electric fields to aid in identifying the sign of charge carriers, the SiV charge capture processes and then compare our results to cryogenic experiments, where SiV0 fluorescence can be detected. Our results resolve long-standing ambiguities about the identity of SiV charge states created by optical illumination and photogenerated carrier capture in diamond