Oxygen Vacancies in Zirconium Oxide as the Blue Luminescence Centers and Traps Responsible for Charge Transport

The origin of luminescence centres and traps of charge carriers in ZrO2 was studied using Raman scattering, luminescence spectroscopy, charge transport and quantum-chemical calculation. After the X-ray irradiation of the ZrO2 film, the EPR spectra from an interstitial oxygen and a negatively charged oxygen vacancy are observed. The 2.7 eV luminescence band and 5.2 eV absorption/luminescence excitation band are associated with an oxygen vacancy. Half of the Stokes shift in blue photoluminescence spectra is equal to the trap thermal activation energy 1.25 eV estimated from the charge transport experiment. Within quantum-chemical simulations and experiments on the extraction of minority carriers from silicon substrates, it was demonstrated that both electrons and holes can be trapped on oxygen vacancies in ZrO2. Hence, oxygen vacancies are supposed to operate as traps responsible for the blue luminescence band and charge transport in ZrO2.