Photophysics of Point Defects in ZnO Nanoparticles

Zinc oxide (ZnO) nanoparticles have recently been identified as a promising candidate for advanced nanophotonics applications and quantum technologies. This work reports the formation of luminescent point defects and describes their photophysical properties. In particular, it is shown using correlative photoluminescence, cathodoluminescence, electron paramagnetic resonance (EPR), and X-ray absorption near-edge spectroscopy that green luminescence at 2.48 eV and an EPR line at g = 2.00 belong to a surface oxygen vacancy (V-o,s(+)) center, while a second green emission at 2.28 eV is associated with zinc vacancy (V-Zn) centers. It is established that radiative point defects can be excited in the visible that exhibits nanosecond lifetimes using both above bandgap and sub-bandgap 405 and 532 nm excitation. This work provides important knowledge towards employment of point defects in ZnO in nanophotonics technologies.