Molecular defects in N-based systems: Common threads and future directions

Single photon emission is a phenomenon where upon proper excitations a system emits one photon at the time. This phenomenon is typical of color centers and localized defects, and it is intriguing for future technologies such communications and cryptography. Recently, single photon emission has been detected in N-based materials such as hexagonal boron nitride (hBN) , GaN, and AlN that have been treated with treatment such plasma bombardment, or laser irradiation. In these systems multiple defect structures have been proposed to lead to single photon emission. However, a clear mechanism of single photon emission is still unclear, even less the possibility for a common one. In this talk, I will present our latest Resonant Inelastic X-Ray Scattering (RIXS) results on N-based materials where in hBN, GaN, and AlN we identify common elementary excitations at 285 meV which produce multiple harmonics extending up to 3 eV. This phenomenology (appearance of multiple harmonics) is not common in the solid state but appears systematically in molecules. Indeed, from our RIXS data we can identify the presence of N2-like defects in hBN, GaN, and AlN and through a systematic analysis we show that there is a correlation between the energy of the RIXS harmonics and the peaks observed by photo-luminescence spectroscopy. Moreover, thanks to an investigation using different nitrogen isotopes we can pinpoint that the reticular nitrogen rather than environmental nitrogen leads to the formation of these molecular defects. The presence of predictable molecular nitrogen in these systems lead to the possibility of targeted stimuli such as cavity confinement and laser excitation in order to trigger single photon emission, which represent a first step into devices.