A role of oxygen vacancy on annealed ZnO film in the hydrogen atmosphere

RF-sputtered ZnO films were annealed in the ambient atmospheres of Ar or hydrogen gas. Hydrogen effects on oxygen vacancies of ZnO films were studied through the characterizations of physical and electrical properties after annealing at 300 °C. The carrier concentration was increased to ∼1017 cm−3 in both annealing ambient atmospheres. On the other hand, the mobility was distinctly decreased when the films were annealed in the ambient atmosphere of Ar gas. Even though the physical structure undergoes small changes regardless of annealing ambient atmospheres, the increase of oxygen vacancies was remarkably suppressed in the annealing ambient atmosphere of hydrogen gas. Two distinct band edge states, generated by oxygen vacancies, are correlated to the changes in carrier concentration and mobility as a function of energy level below the conduction band.