Suchergebnisse

The development of a facile method to obtain materials with piezoelectric properties, through a green synthesis, as an alternative to lead-free materials, was the main objective of this work. Piezo active materials were grown by chemical methods on two types of metal substrates: Pt/Ti/SiO2/Si and the Ti foil. Ag and Li-doped ZnO nanostructures were prepared by hydrothermal method at low temperature on metallic substrates which were previously covered with ZnO seed layer deposited by spin coating sol-gel method. The newly prepared materials were covered with a polymer layer and were morphological characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The piezoelectric properties were estimated by measuring the direct piezoelectric coefficient d33. The test results show that the doped ZnO nanostructures synthesized using a green route exhibit a piezoelectric response so the established method can be considered a promising approach for obtaining piezoelectric materials on large surfaces. Piezo active nanostructures could be of interest for integration into piezoelectric devices.

The multilayer (10 layers) Al doped ZnO (AZO) thin films were deposited on glass substrate by sol-gel & dipping method. X-Ray diffraction measurements showed that the AZO films were polycrystalline with a hexagonal wurtzite structure. The morphological properties of the films were analyzed by atomic force microscopy showing continuous and homogeneous film, completely covering the substrates. The thickness, optical constants, optical band gap (Eg) and transmittance (T) of AZO films were assessed by spectroscopic ellipsometry on UV-vis-NIR spectral range. The AZO film has high transmittance above 80% in the visible region and the optical band-gap energy around 3.7 eV. The electrical characteristics regarding conductivity, mobility and carrier concentrations, were measured by Hall Effect measurements (van der Pauw method). The bulk carrier concentration of the AZO film with 10 layers was found to be 1.16x1019 cm-3. The vibrational bands were obtained by Raman analysis. Defects due to oxygen vacancies in the prepared AZO films were evidenced by photoluminescence spectroscopy (PL). The optical and electrical properties of the AZO thin films proved the possibility to be used in optoelectronic applications.