Structural and piezoelectric properties of pulsed laser deposited ZnO thin films

Zinc oxide thin films were obtained on Pt-coated silicon, r-cut sapphire and MgO substrates by laser ablation of a Zn target in oxygen reactive atmosphere, the oxygen being supplied either by a standard gas inlet valve or from a radiofrequency (RF) oxygen plasma. The influence of the deposition parameters, i.e., laser wavelength (266 nm, 355 nm, 1064 nm), laser fluence (1.5–20 J/cm2), oxygen pressure (1–60 Pa), and of RF plasma beam addition on the morphological properties of zinc oxide films was particularly investigated. Before piezoelectric measurements the obtained films, with thicknesses in the range 50 nm–4 ìm have been characterized by Atomic Force Microscopy (AFM), X-ray diffraction (XRD), and Transmission Electron Microscopy (TEM). The acoustic properties of the ZnO layers have been tested by implementing a surface acoustic wave (SAW) delay line. Frequency domain and time domain measurements have been performed using a Network Analyzer (HP8753A). Before the realization of the device, theoretical calculations of SAW propagation along the multilayered structures have been performed using the PC Acoustic Wave Software, from McGill University (Canada), considering the substrate as semi-infinite. The obtained results have been correlated with theoretical simulations.