Growth properties and structural analysis of ZnO films and of Au clusters on ZnO

We have studied the possibility to grow O-terminated ZnO(0 0 0 1̄) films on Al2O3 substrates with high epitaxial quality. After growth via sputtering methods, the ZnO films were annealed to increase the film quality resulting in a mosaicity of 0.60° and a surface roughness of <3 Å. Finally, gold films were sputtered at room temperature on the surface. The structural properties of the samples were investigated by X-ray scattering, reflection high-energy electron diffraction (RHEED) and by atomic force microscopy (AFM). AFM images clearly demonstrate that gold films with a nominal thickness of <50 Å form clusters, which can be as high as 300 Å. X-ray diffraction (XRD) studies reveal a predominant (1 1 1) texture of the clusters. Further deposition of Au leads to coalescing clusters smoothing out the surface.