METHOD FOR THE PREPARATION AT LOW TEMPERATURES OF FERROELECTRIC THIN FILMS, THE FERROELECTRIC THIN FILMS THUS OBTAINED AND THEIR APPLICATIONS

摘要

A processing technology is for the fabrication at low temperatures of ferroelectric crystalline oxide thin films, among others PbZr_xTi_1-xO₃ (PZT) (400° C. for PZT) with ferroelectric properties appropriate for integration in devices. The method is also for the fabrication of ferroelectric thin films of bronze tungsten (A₂B₂O₆), perovskite (ABO₃), pyrochlore (A₂B₂O₇) and bismuth-layer (Bi₄Ti₃O₁₂) structures, in which A and B are mono, bi-, tri-, tetra- and pentavalent ions. The method is based on the combination of Seeded Diphasic Sol Gel (SDSG) precursors with Photo Chemical Solution Deposition (PCSD) methodology and comprises the main following steps: i) synthesis of a modified metal-organic precursor solution of the desired metal oxide composition with a large photo-sensitivity in the UV wavelength range; ii) preparation by a sol gel process of nanoparticles of the desired composition, similar or dissimilar to the crystalline compound to be obtained from the previous precursor sol; iii) dispersion of the crystalline nanoparticles in the precursor sol to prepare a stable and homogeneous sol-gel based suspension; iv) deposition of the previous suspension onto substrates; v) UV irradiation in air or oxygen of the deposited layer and further thermal treatment in air or oxygen of the irradiated layer at temperatures below 400° C. The method provides for the fabrication of polycrystalline ferroelectric, piezoelectric, pyroelectric and dielectric thin films, dense and without cracks with thickness above 50 nm and below 800 nm on single crystal, polycrystalline, amorphous, metallic and polymeric substrates at low temperatures and with optimised properties, being applicable in microelectronics and optics industries.