Structural, electrical and optical properties of ZnO:AlF3 thin films deposited by RF magnetron sputtering

Abstract

Both the effects of RF power and thermal annealing temperature on AlF3 doped ZnO thin films were discussed in the paper. Structural, electrical, and optical characterizations were used to evaluate the properties of the film. Results showed that the growth of c-axial preferential ZnO (002) was not disturbed by the variations of RF powers applied on the AlF3 target. The optical bandgap of the film increased from 3.28 to 3.74eV as the power increased from 0 to 125W. A high quality ZnO:AlF3 film was obtained at the power ratio of 100W/75W applied on ZnO/AlF3. This film showed a low resistivity of 3.60×10−2Ωcm, carrier concentration of 4.06×1020cm−3, mobility of 0.62cm2/Vs, and transmittance of 85% in the visible region. The small addition of fluorine and aluminum addition to the ZnO film resulted in the increase of carrier concentration as well as increase in Hall mobility. These effects were due to the addition of fluorine which caused the ionized point defects to be removed. An excessive addition of fluorine and aluminum to the ZnO increased grain boundary scattering, resulting in a decrease of Hall mobility. The crystallinity and Hall mobility of the films were further improved after thermal annealing.