Evaluation of oxygen vacancy in ZnO using Raman spectroscopy

Oxygen vacancies in zinc oxide (ZnO) are intrinsic defects, which are easily generated during crystal growth or device processing. Investigations of defects, such as oxygen vacancies, are important to understand the properties of ZnO. In this study, we attempt to quantify oxygen vacancies in ZnO powders using Raman spectroscopy. ZnO powder is reduced in a hydrogen atmosphere at 300-600 °C for 30-90 min. The peak position of the E ₂ (high) mode, which is related to the oxide ion vibration, shifts toward a lower frequency as the oxygen vacancies increase. Upon re-oxidation, the initial E ₂ (high) peak position is restored. Because the E ₂ (high) peak shift is scaled with the amount of oxygen vacancies, this relationship can be used to estimate the amount of oxygen vacancies.