Heteroepitaxial Relation and Optical Properties of Cu-Doped ZnO Films Grown by Using Pulsed Laser Deposition

In this study, epitaxial Cu-doped (0.2, 0.4, 0.6, 0.8, 1, 2, 3 mol%) ZnO (CZO) films were deposited on Al2O3 (006) substrates. The substrate temperature during deposition was maintained at temperatures ranging from room temperature (R.T.) to 600 degrees C and the oxygen flow rate was 10 sccm. The full width at half maximum (FWHM) of the CZO films was <0.18 degrees, which was attributed to the low lattice-mismatch of 0.19% between the film and the substrate according to the extended atomic distance mismatch (EADM) relationships. The phi-scan of the CZO (112) reflection showed six-fold-like symmetric peaks, indicating specific in-plane epitaxial growth patterns of the CZO/Al2O3 substrate. The depth profiles of the CZO films confirmed the presence of zinc, oxygen and copper distributed uniformly throughout the entire film. The CZO films showed a high transmittance (>90 %) at a 600-nm wavelength. The variations ill the band gap energy (E-g = 3.13 - 3.28 eV) and the deep level emission (DLE) for the CZO films with the deposition temperature and the Cu doping content ratio are also discussed.