Red emission doublets in diamond from vacancies interacting with interstitial carbon aggregates in tunneling configurations

Carbon vacancies in diamond are emerging as light emitting systems with outstanding properties for photonics and quantum information. The feasibility of these applications is strictly related to specific spectral and kinetic features of vacancy light emissions which, in turn, depend on the environment of the light-emitting sites. Many vacancy variants are known, from the intrinsic one to those perturbed by N and Si atoms. However, no data is available on light emissions of vacancies interacting with interstitial carbon aggregates, despite the intrinsic nature of such systems. Here we report the analysis of two emission doublets at 1.87 and 1.82 eV, and at 1.76 and 1.71 eV. The latter is systematically accompanied by the infrared signature of interstitial carbon platelets at 1365 cm−1 and low-energy sidebands with 8 and 16 meV splitting, tentatively assigned to tunneling modes of the split-interstitial over four equivalent configurations. Energy splitting and photon energies are consistent with vacancies at interstitial carbon structures from previous first principle calculations which find here, for the first time, an experimental confirmation in photoluminescence spectra. The data has potential to open up a new technology by controlling vacancy generation and patterning in diamond via laser writing of oriented interstitial layers