Investigation On Poly-domain Switching Of PZT Ferroelectric Thin Film Preparation By SOL-GEL Method Under Applied Fields

Ferroelectric materials have excellent piezoelectric, ferroelectric, pyroelectric, dielectric and excellent optical properties as a function of mechanical and electrical conversion materials, and play an important role in the field of high technology. Lead zirconium titanate piezoelectric ceramics has become the most widely used piezoelectric material because of its excellent performance. In recent years, researchers and engineers have been focused on the ferroelectric material, because of the ability of conversion the electromagnetic, heat energy, mechanical energy for the charge. Ferroelectric materials has been used in many electronic applications, such as: nonvolatile ferroelectric memory, pyroelectric detector, pressure electric sensor, ultrasonic transducer, film capacitors, microelectromechanical systems(MEMS).Lead titanate(PZT) ferroelectric thin films prepared by sol gel method in this paper, the preparation of lead titanate(PZT) ferroelectric thin film was prepared by spin coating, low temperature heat treatment and high temperature crystallization process. Lead acetate、zirconyl nitrate、tetrabutyl titanate were used as the sources of Pb, Zr and Ti, and glacial acetic acid was used as catalyst, acetyl acetone and methyl amide as additives to prepare precursor sol. We spin coating the film with a KW-4A type machine, and the film was annealed at high temperature by KBF1100- box type furnace. In the process of preparing films, we respectively analysis sensitive factors of sol configuration phase, spin coating stage, high temperature annealing crystallization stage analysis, to explore the influence of solvent, p H value, amount of water, concentration, additive, precursor monomer solution mixing method, a base, a rotary coating, annealing temperature on the quality of the films, and ultimately to determine the process for preparing thin films. At last, we prepare the film with the(111) preferred orientation, surface roughness and piezoelectric response clear on Pt/Ti/Si O2/Si substrate, and the residual polarization Pr was 45 C/cm2, and the coercive field Ec was 1000 k V/cm,the thick of the film was307.4nm,559.73 nm,647.11 nm.Scanning electron microscopy, XRD, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, thermal gravimetric analysis, atomic force microscopy and piezoresponse force in response to a microscope were used to measure and analysis the thin films. We found that under the conditions that concentration of 0.4M, p H value of 4.5, solvent for ethylene glycol methyl ether, the use of step growth rate of rotating film and rapid heat treatment parameters to prepare the film which surface is smooth, and(111) preferred orientation. The test results of atomic force microscope show that the average roughness of Ra is 1.79 nm, and the mean square root roughness of Rq is 2.23 nm. The results of XRD analysis show that the Pt/Ti/Si O2/Si substrate is more suitable for the crystallization of the thin films and the formation of the perovskite structure compared with the Si O2 and Si substrates. When the annealing time is the same, the atomic ratio of the film prepared under 650℃ is close to the ideal value, and it is the most beneficial to the formation of the perovskite. The VPFM module of the atomic force microscope is used to measure the PFM amplitude of the butterfly curve, which proves that the piezoelectric properties of the film are better.The thin film surface was patterned and etched by using lithography technology. By atomic force microscopy and micro nano processing method to realize the film surface micro structure fabrication.By piezoresponse force microscopy(PFM),the ferroelectric domains of thin films were measured.PFM phase diagram results show that polarization direction to 360 degree change, illustrates the preparation of ferroelectric thin films with good performance. PFM amplitude map shows that the piezoelectric coefficient of the thin film surface is uniform. It shows that the piezoelectric properties were uniform. We use PFM to carry on the electric domain reversal under the electric field action, in the voltage of 3V, the polarization direction of the film is 180 degrees, and the film changes from the multi domain state to the single domain state. We have used the atomic force microscope to process the micro structure of the thin film for the domain test, and found that the role of force, the same will make the film toward the development of single domain state. The possibility of controlling the ferroelectric properties of the material by controlling the ferroelectric domain is demonstrated.