Structural characterization of Zr-doped ZnO films deposited on quartz substrates by reactive radio frequency magnetron co-sputtering

Zr-doped ZnO (Zn1-xZrxO, 0 <= x <= 0.067; ZZO) thin films were grown at room temperature by reactive radio frequency co-sputtering on quartz substrates The ZZO films have a strong preferred orientation toward the c-axis but this orientation weakened as x increased. The size of crystallites of the ZZO films decreased and the surfaces of the ZZO films smoothened as x increased. The Zn atom were divalent and slightly affected only in the c-axis. Zn K-edge X-ray absorption near edge structure (XANES) spectra of the ZZO films show that the Zn atom were divalent and slightly affected only in the c-axis. The Zr atoms were tetravalent and their K-edge XANES spectra were slight different from that of ZrO2. Polarization-dependent Zn K-edge extended x-ray absorption fine-structure (EXAFS) spectra revealed that the local structural variation was stronger along the c-axis than along other axes. The Zn atom site was well replaced by Zr atom regardless of x. Average optical transmittance in the visible region was >= 90%, and as x increased, optical band gap increased and blue-shifted.