Formation and evolution of oxygen vacancies in ZnO white paint during proton exposure

The formation and evolution of oxygen vacancies in ZnO white paint during <200 keV protons exposure was investigated using photoluminescence spectroscopy. After irradiation, the shape of photoluminescence spectra changes little, but the peak height decreases. With increasing fluence, the amount of doubly ionized oxygen vacancies decreases, while that for the singly ionized oxygen vacancies increases. The former can trap electrons in the conduction bands to become the singly ionized oxygen vacancies, leading to that the latter gradually becoming the major defects induced by irradiation. The increase in content of singly ionized oxygen vacancies due to the irradiation can also promote an increase in the amount of absorbed oxygen in the paint, enhancing the quenching effect of photoluminescence and thus decreasing the photoluminescence peak.