Influence of external magnetic field on properties of aluminum-doped zinc oxide films prepared by RF magnetron sputtering

Al-doped ZnO (AZO) transparent conductive oxide films were prepared by RF magnetic sputtering. An external magnetic field was applied to the traditional magnetron sputtering system. The influence of the external magnetic field on the crystalline structure, surface topography and photoelectric properties of the AZO transparent conductive film have been studied. XRD diffraction patterns show that under the same processing condition, the intensity of (002) diffraction peak is significantly increased with the external magnetic field, suggesting a higher degree of c-axis preferred orientation. Scanning electron microscope shows that the external magnetic field can enlarge the grain size and density of films; the surface topography of the AZO films deposited without an external magnetic field is wormlike. Deposition rate and square resistance test results show that in an external magnetic field, the deposition rate will increase from 13.04 nm/min to 19.93 nm/min, and the sheet resistance reduce to 12.88 Omega/square from 30.74 Omega/square at a sputtering time of 90 min. Optical transmittance spectra shows that the average transmittance of all the films in visible light spectrum is over 85% when the sputtering time is not more than 60 min, while the external magnetic field has little effect on the transmittance of the films, but making a larger blue shift of the absorption edge. Ansys software is used to simulate the two-dimensional magnetic field distribution above the target. Results show that the intensity of the horizontal magnetic field and the uniformity of it are improved by the external magnetic field, the secondary electrons near the target are tightly bound, leading to a much larger target current intensity. So the deposition rate, surface topography and photoelectric properties of the AZO films are improved.