Low wet etching rates of ZnO films prepared by sputtering of mixed ZnO and AlN powder targets

ZnO films codoped with Al and N have been prepared by radio frequency magnetron sputtering in an Ar atmosphere, using targets of mixtures of ZnO and AlN powders. The Al-doped ZnO films are transparent, whereas the films codoped with Al and N are colored. The Al- and N-concentrations in the colored films are estimated to be 4–7 at.% and 1–2 at.%, respectively. No enhancement of the carrier density is seen in the colored ZnO films, whereas the colored films exhibit lower etching rates of 3–5 nm/s in a 0.1 M HCl solution, in comparison with the Al-doped ZnO films. For the colored film, the anisotropic grain growth occurs, and cubic grains are produced after etching. The low etching rates of the colored films are ascribed to the epitaxial growth of AlN films on the surfaces of ZnO grains, rather than the incorporation of Al–N and Al–O bonds into the ZnO lattice.