Deposition of Al-doped and Al, Sc-co-doped zinc oxide films by RF- and DC-sputtering of the ZnO and Al–xSc (x = 0, 0.4, 0.8 and 1.7 wt.%) targets

Innovative films ZnO: Al–xSc (in which x = 0, 0.4, 0.8 and 1.7 wt.%) were prepared through RF-sputtering on the ZnO target and DC-sputtering on the Al–xSc alloy targets. X-ray diffraction (XRD) of the films displayed a hexagonal wurtzite textured at (002) and the peak (002) shifted to a little higher angle with increasing the Sc-content in the films. Transmission electron microscopy (TEM) revealed smaller uniform columnar grains (diameter around 65 nm) in the ZnO: Al–xSc films than in the ZnO: Al. The transmittance was higher than 80% for all the films and the adsorption edge indicated a blue-shift for the films ZnO: Al–0.4 wt.%Sc and ZnO: Al–0.8 wt.%Sc but a red-shift for the film ZnO: Al–1.7 wt.%Sc. The electrical conductivity (S/cm) of the films increased from 2.64 × 102 to 7.94 × 102 with increasing of wt.%Sc from 0 to 1.7 in the target, due to the increase in both the electron concentration and electron mobility. X-ray photoelectron spectroscopy (XPS) analysis inferred that higher electrical conductivity of the films is ascribed to the deficient oxygen (i.e., O(III)). The corrosion resistance of the films in 3.5% NaCl increased with increasing the Sc-content.