Doubly charged silicon vacancy center, Si-N complexes, and photochromism in N and Si codoped diamond

Diamond samples containing silicon and nitrogen are shown to be heavily photochromic, with the dominant visible changes due to simultaneous change in total ${\mathrm{SiV}}^{0/\ensuremath{-}}$ concentration. The photochromism treatment is not capable of creating or destroying SiV defects, and thus we infer the presence of the optically inactive ${\mathrm{SiV}}^{2\ensuremath{-}}$ . We measure spectroscopic signatures we attribute to substitutional silicon in diamond, and identify a silicon-vacancy complex decorated with a nearest-neighbor nitrogen $\mathrm{SiVN}$, supported by theoretical calculations.