Epitaxial growth and optimization of ZnO films by pulsed laser deposition

ZnO films have been grown on sapphire (0001) substrates by using the pulsed laser deposition technique with a KrF excimer laser (lambda = 248 nm) ablating the target. X-Bay diffraction, photoluminescence, and spectroscopic ellipsometry were applied to characterize the structural and optical properties of the films. High-quality epitaxial ZnO films were obtained at the optimized conditions of 500 degreesC and 200 mTorr. The X-Bay diffraction theta/2theta scan and the in-plane phi-scan revealed an epitaxial relationship between the ZnO film and the sapphire substrate of (0001)(ZnO) // (0001)(sapphire) and [10 (1) over bar0](ZnO) // [11 (2) over bar0](sapphire). The photoluminescence of ZnO films was found to depend strongly on the growth temperature. Intensive ultraviolet emissions were observed from ZnO films as the fabrication temperature was increased from 100 degreesC to 500 degreesC. The refractive indices and the extinction coefficients were obtained by fitting the spectroscopic ellipsometry data, Delta and Psi, using the Forouhi-Bloomer dispersion relation.