Effects of secondary magnetic field on the properties of Al-doped ZnO films prepared by RF magnetron sputtering

The effects of secondary magnetic field originating from a permanent magnet on deposition rate, crystalline structure and photoelectric properties of Al-doped ZnO (AZO) films prepared by RF magnetron sputtering were systematically investigated. X-ray diffraction demonstrated that the films prepared using a secondary magnetic field were well aligned and textured along (0 0 2) orientation. SEM micrographs revealed that the grains became more compact and homogeneous with fewer defects in comparison to those grown by conventional magnetron sputtering (CMS). The deposition rate and lowest resistance of films prepared in the presence of a secondary magnetic field were 19.9 nm/min and 12.88 Ω/□, respectively. The average transmittance of all films in visible range was over 85% when the sputtering time was less than 60 min. The secondary magnetic field had a small influence on the transmittance of the films, but it caused a larger blue shift of the absorbance edge. Numerical simulations showed that the secondary magnetic field significantly changed the intensity and distribution of the transverse magnetic field in discharge space and caused a higher target current density.