O3 Thick Films Research Articles

Effect of Carrier Gas Species on Ferroelectric Properties of PZT/Stainless‐Steel Fabricated by CO2 Laser‐Assisted Aerosol Deposition

Pb(Zr,Ti)O3 (PZT) thick films were deposited onto stainless‐steel substrates by aerosol deposition using different kinds of carrier gases and were irradiated by CO2 laser both during and after deposition, for the recovery of ferroelectricity. The ferroelectric and dielectric properties of PZT films deposited using oxygen and nitrogen gases and irradiated by CO2 laser were superior to those of films deposited using He gas and irradiated by the laser. Some kinds of defects within the film were relaxed by CO2 laser irradiation during deposition, and grain growth in the film was promoted by post‐annealing using laser irradiation.

Low-temperature synthesis of (Pb,La)(Zr,Ti)O3 thick film on Ti substrates by the hydrothermal method using oxide precursors

We simplified the hydrothermal process using oxides instead of liquid-base reactants as precursors. Lead lanthanum zirconate titanate Pb0.94La0.06(Zr0.65Ti0.35)0.985O3 (PLZT) thick films were prepared on Ti substrates at 150°C via hydrothermal synthesis. The films with a single perovskite structure were smooth and the surfaces were free of micrometer scale cracks. The thickness of the film was about 56μm. The dielectric constant and dielectric loss were 665 and 0.03, respectively, at 1MHz. Even at high frequencies the dielectric properties of the PLZT film still remain stable. The samples showed excellent reproducibility in the measurement of leakage current.

Fabrication of Microcantilever Sensors Actuated by Piezoelectric Pb(Zr0.52Ti0.48)O3 Thick Films and Determination of Their Electromechanical Characteristics

AbstractThe integration and the device realization of Pb(Zr, Ti)O3 (PZT) thick films on Si substrates are known to be extremely difficult because the processing temperature of the PZT thick film is close to the melting point of Si. However, PZT thick‐film devices on Si warrant attention as they are appropriate for biological transducers; they generate large actuating forces and have a relatively high sensitivity for mass detection, especially in liquids. In this study, Pb(Zr0.52Ti0.48)O3 thick‐film cantilever devices are successfully fabricated on a Pt/TiO2/SiNx/Si substrate using a screen‐printing method and microelectromechanical systems (MEMS) process. Elastic and electromechanical properties such as the Young's modulus and transverse piezoelectric coefficient are determined from microstructural and electrical analyses for further mechanical study. The calculated Young's modulus of the thick film, 53.9 ± 3.85 GPa, corresponds to the resonant frequency obtained from the measured harmonic oscillation response. The transverse piezoelectric constant, d31, of –20.7 to –18.8 pC N–1 is comparable to that of a dense thin film. These values promise the possibility of determining the resonance properties of a thick‐film cantilever by designing its structure and then simulating the harmonic oscillation response. Using the PZT thick‐film cantilever, a strong harmonic oscillation with a quality (Q) factor of about 23 is demonstrated in water. The observation of strong harmonic oscillation in liquid implies the feasibility of precise real‐time recognition of biomolecules using PZT thick‐film cantilevers.

Dependence of electrical properties of epitaxial Pb(Zr,Ti)O3 thick films on crystal orientation and Zr∕(Zr+Ti) ratio

Epitaxial Pb(Zr,Ti)O3(PZT) films, 1.5–2.0μm in thickness, with a Zr∕(Zr+Ti) ratio ranging from 0.20 to 0.75 were grown on (100)c-,(110)c-, and (111)c-oriented SrRuO3∕∕SrTiO3 substrates at 600 °C by metal-organic chemical vapor deposition (MOCVD). The effects the Zr∕(Zr+Ti) ratio had on the crystal structure, dielectric and ferroelectric properties, and piezoelectric response of these films with different crystal orientations were systematically investigated. We ascertained from x-ray-diffraction reciprocal-space-mapping analysis that (001)T-∕(100)T-∕(100)R-,(101)T-∕(110)T-∕(110)R-∕(101¯)R-, and (111)T-∕(111)R-∕(111¯)R-oriented films had epitaxially grown on the respective (100)c-,(110)c-, and (111)c-oriented SrRuO3∕∕SrTiO3 substrates. The constituent phase changed from a tetragonal single phase, a mixture phase of a tetragonal and rhombohedral, to a rhombohedral single phase with increasing Zr∕(Zr+Ti) ratio irrespective of the orientation of the substrates. However, the range of the Zr∕(Zr+Ti) ratio of the film with the mixture phase differed depending on crystal orientation. This suggests that the stress relaxation process applied from the substrates changed due to crystal orientation. The relative dielectric constant was maximum for films with the mixture phase regardless of the crystal orientation. Remanent polarization was also maximum for these films on the (111)cSrRuO3∕∕SrTiO3 substrates, while it was minimum on the (100)c- and (110)c-oriented SrRuO3∕∕SrTiO3 substrates. Films with two phases coexisting had larger electric-field-induced strain than films with a single tetragonal or rhombohedral phase for the (111)-oriented films, but there were no remarkable changes in the (100)- and (110)-oriented films. Small ac signal measurements suggested that domain-wall motions easily occurred in the (111)-oriented films with the mixture phase compared with other orientations. These results indicated that the larger field-induced strain of the (111)-oriented PZT films consisting of a mixture of tetragonal and rhombohedral phases largely contributed to extrinsic factors such as domain-wall motions and phase transformation due to the applied electric field.

High-Speed Optical Microscanner Driven with Resonation of Lam Waves Using Pb(Zr,Ti)O3 Thick Films Formed by Aerosol Deposition

A high-performance optical microscanner with a resonance frequency over 20 kHz and a scan angle (peak-to-peak value) over 30° in atmospheric ambient, was successfully fabricated by deposit piezoelectric materials at a high rate by the AD method onto a metal scanner structure, which was fabricated by mechanical machining. The scanner is applicable to SVGA high-resolution display of 800×600 or more. This method is a powerful tool for realizing ceramic integration with metal components.

Preparation of transparent ferroelectric Pb0.92La0.08Ti0.96O3 thick films on ITO-coated glass substrates by a sol–gel route

Pb0.92La0.08Ti0.96O3 films with thickness between 580 nm and 1830 nm were deposited on ITO-coated glass substrates using a sol–gel process under a relative low temperature of 580 °C. The films are crystallized well and of pure perovskite polycrystalline structure, and the surface of the films was smooth and condense. With the increase of the film thickness, the grain size and dielectric constants of the films increase. The dielectric constant-voltage curves are symmetric about a zero-bias axis and showed the hysteresis for all the films. In addition, the coercive field Ec decreases with the film thickness. All the films are transparent and the absorption edges were found to shift to longer wavelength with increasing thickness of the films. The refractive index (n) and extinction coefficient (k) of 1830 nm thick film are 2.39 and 0.009, respectively, at 633 nm wavelength.

Damage‐Free and Short Annealing of Pb(Zr,Ti)O3 Thick Films Directly Deposited on Stainless Steel Sheet by Aerosol Deposition with CO2 Laser Radiation

Pb(Zr,Ti)O3 (PZT) thick films directly deposited onto stainless steel (SS) sheets by the aerosol deposition method were annealed by CO2 laser (CL) radiation. The surface brilliance of the SS sheets was not influenced by thermal heating and the temperature of the reverse side of the film (i.e., the SS sheet) was measured at 150°C or less. The remanent polarization, coercive field values, and the dielectric constant are 27.8 μC/cm2, 31.6 kV/cm, and 1366, respectively. The diffusion layer between the PZT and the SS sheet was minimized by the use of CL radiation compared with using an electric furnace.

Preparation of Ba(Ti,Zr)O3 Thick-Film Microactuators on Silicon Substrates by Screen Printing

BaTi0.975Zr0.025O3 thick-film microactuators were fabricated by combining screen printing and silicon micromachining. The electric properties of BaTi0.975Zr0.025O3 thick films with a small area on a Pt bottom electrode using silicon substrates prepared by screen printing were investigated. The thick films were fired in the temperature range from 1310 to 1370°C. The remanent polarization Pr and coercive field Ec were 6.2 µC/cm2 and 1.8 kV/cm at the firing temperature of 1350°C, respectively. The effective piezoelectric constant d33 calculated from a unipolar signal curve was approximately 120 pm/V for the thick film fired at 1350°C. After measuring the electric properties of BaTi0.975Zr0.025O3 thick films, microactuators were fabricated by etching the substrates. The displacement of a microactuator that has a 0.3×0.3 mm2 area membrane and is driven at 40 Vpp and 4 kHz was approximately 0.12 µm. This indicates the possibility of applying this microactuator in lead-free micropump or micromixer devices.

(111) Preferred Oriented Pb(Zr,Ti)O3 Thick Films Prepared by Multilayer Process and Its Application to Ultrasonic Sensors

We report the deposition of Pb(Zr0.52Ti0.48)O3 (PZT) thick films on Pt/Ti/SiO2/Si substrates using a multilayer process to suppress the problem of crack formation due to thermal stress. The thickness dependences of film structure, ferroelectric and dielectric properties were investigated over the thickness range of 0.24–4.6 µm. A strong (111) orientation was obtained from all films deposited in the experiments. For a constant applied field of 170 kV/cm, remanent polarization, 2Pr developed from 14 µC/cm2 to 60 µC/cm2, as film thickness increased from 0.24 to 4.6 µm. Dielectric constant also increased with film thickness, and reached the maximum value of 1300 at the thickness of 4.6 µm. These trends were interpreted in terms of the interfacial effect on the electrical characteristics. A thin-film-type ultrasonic sensor was fabricated by depositing a multilayered PZT thick film onto an SOI substrate having a membrane structure, and its characteristics are reported.

Preparation and optical waveguide property of metal alkoxide solution-derived Pb(Zr0.5Ti0.5)O3 thick films

Pb(Zr 0.5 Ti 0.5 ) O 3 films with thickness of about 1.5 and 3.7 μm have been deposited on single-crystal SrTiO3 substrate by a sol-gel process from nonhydrolyzed metal alkoxide precursor. X-ray diffraction shows that the films exhibit a single perovskite phase with (001)-preferred orientation. Atomic force microscopy study indicates that the PZT film possesses a crack-free and smooth surface. The optical waveguide property has been examined by the prism-film coupling experiment. Four and 12 TE modes are observed for 1.5 and 3.7 μm PZT films, respectively.

Gas Sensing with Nanocrystalline Magnetic Perovskite Oxides

LaFeO3 LFO, La0.8Sr0.2FeO3 LSFO and LaMg0.1Fe0.9O3 (LMFO) thick films were prepared by screen printing from oxide powders made by the solgel citrate method. Their structural, electrical and gassensing properties at exposure to various gases, such as carbon monoxide (CO), nitrogen dioxide (NO2), methane (CH4) and ethylene (C2H4), are reported. The results of X-ray diffraction experiments show that these compounds have orthorhombic crystal structure. The substitutions of Sr2+ ion for La3+ in the A-site and Mg2+ ion for Fe3+ in the B-site in the perovskite ABO3 structure change only slightly the values of the lattice constants, but to a much larger extent electrical properties of the base material. LaFeO3 showed very good sensing performance to environmental monitoring of various gases at different operation temperatures. In addition, all LFO, LSFO and LMFO thick films were very sensitive to C2H4.

Comparison Study of (001)-/(100)-Oriented Epitaxial and Fiber-Textured Pb(Zr,Ti)O3 Thick Films Prepared by MOCVD

(001)-/(100)-oriented epitaxial PZT films and fiber-textured PZT films with a thickness of 2 μ m were deposited on (100) c SrRuO3//(100)SrTiO3 and (111)Pt/TiO2/SiO2/(100)Si substrates, respectively, by metalorganic chemical vapor deposition (MOCVD). Crystal structure and the electrical properties were compared for epitaxial PZT films with those of fiber-textured ones, which had the same out-of-plane orientation but different in-plane orientation. The constituent phase change from the single phase of tetragonal PZT, mixture phases of tetragonal and rhombohedral ones and the single phase of rhombohedral one for both films when the Zr/(Zr + Ti) ratio increased. The out-of-plane lattice parameter of (001)- and (100)-axes of PZT films were almost the same value for both films. This indicates the residual strain in the PZT films was almost the same. Dielectric constant (ϵ r) took the maximum value around the MPB composition for (001)-/(100)-oriented fiber-textured films but was almost independent of the Zr/(Zr + Ti) ratio for epitaxial ones. Moreover, there was no significantly dependence of remanent polarization (P r) value on the Zr/(Zr + Ti) ratio for (001)-/(100)-oriented fiber-textured films, while it took minimum value near the morphotropic phase boundary (MPB) for epitaxial ones.

Preparation of Ba(Ti,Zr)O3 Thick Films on Silicon Substrate by Screen Printing

BaTi0.975Zr0.025O3 thick films were prepared by a screen-printing method on Pt bottom electrodes using silicon substrates in the firing temperature range from 1330°C to 1370°C. The high-temperature sintering of Pt bottom electrodes and Ba(Ti,Zr)O3 thick films was successfully achieved using silicon substrates with a fairly thick oxide layer. The ferroelectric and piezoelectric properties of the thick films were examined. The remanent polarization of the thick films increased with increasing firing temperature. A remanent polarization of 13.8 µC/cm2 for a Ba(Ti,Zr)O3 thick film was obtained at a firing temperature of 1370°C. The longitudinal piezoelectric constant d33 calculated from a unipolar signal (10 kV/cm, 1 Hz) curve was 610 pC/N for the thick film fired at 1370°C.

Compositional Dependence of Electrical Properties of Highly (100)-/(001)-Oriented Pb(Zr,Ti)O3 Thick Films Prepared on Si Substrates by Metalorganic Chemical Vapor Deposition

Pb(Zr,Ti)O3 (PZT) films having 2.0 µm in thickness with the Zr/(Zr+Ti) ratio ranging from 0.20 to 0.75 were prepared on (111)Pt/TiO2/SiO2/(100)Si substrates at 600°C by metalorganic chemical vapor deposition (MOCVD). Highly (100)-/(001)-oriented PZT films were successfully prepared with a deposition rate of 1.5 µm/h. Effects of the film composition on the crystal structure, ferroelectricity and electric field-induced strain of these films were investigated. It was ascertained by θ-2θ scans of X-ray diffraction that a tetragonal single phase and a rhombohedral single phase were obtained for the films with the Zr/(Zr+Ti) ratio below 0.40 and above 0.60, respectively. On the other hand, the mixed phases with tetragonal and rhombohedral phases were observed for the Zr/(Zr+Ti) ratio ranging from 0.43 to 0.57. This composition is similar to the morphotropic phase boundary (MPB) for the bulk ceramics. Remanent polarization (Pr) and coercive field (Ec) were almost constant and monotonically decreased, respectively, when the Zr/(Zr+Ti) ratio increased. This change of Ec value with the Zr/(Zr+Ti) ratio was in good agreement with the reported one for the sintered body, but not for the Pr value. On the other hand, the relative dielectric constant and the field-induced strain took maximum values around this composition which was in good agreement with the reported data for the sintered body. Field-induced strain was in good agreement with the estimation from the phenomenological equation, and the large change of polarizations is found to cause large field-induced strain. These results show that the highly (100)-/(001)-oriented films showed behavior similar to that of a PZT sintered body in terms of field-induced strain, coercive field and the dielectric constant together with the coexistence of the tetragonal and rhombohedral phases around the MPB composition.

Microstructure and electrical properties of Pb(Zr, Ti)O3 thick film prepared by electrostatic spray deposition

Abstract Strongly pervoskite (1 0 0)-oriented lead zirconate titanate (PZT) films were prepared by the electrostatic spray deposition (ESD). The microstructure and crystalline-granular texture of the films were investigated by scanning electron microscope (SEM) and atomic force microscope (AFM), respectively. The films deposited at substrate temperature of 25 °C and 100 °C were found to have the same crystallite-size distribution around 150–200 nm. With given properties of the spray cloud and the precursor solution, well-crystallized PZT thick films with dense microstructure can be obtained at low deposition temperature. The relative dielectric constant of the 2 μm thick ESD-deposited PZT films with sol–gel PZT films as intermediate layers was as high as 960. The films also exhibit excellent remanent polarization and coercive fields of 12.5 μc/cm2 and 32 kV/cm, respectively.

Electrical properties and chemical compatibility of PZT thick film on Ni substrates

The characteristics of Pb(Zr,Ti)O3(PZT) thick films that were printed and fired on Ni substrates were studied. The dielectric characteristics of samples sintered at 850°C on Ni substrates could not be measured due to the formation of a NiO layer at the Ni/PZT interface. The scanning electron microscope and energy dispersive X-ray analysis of cross-sections of the PZT thick films on Ni substrates, and of a mixture of PZT and NiO powders, fired at 850°C, did not indicate the formation of secondary phases. However, the transmission electron microscopy showed around 8% solid solubility of NiO in the PZT. A new structure with a prefired, Au thick-film layer was designed in order to prevent the diffusion of the NiO to the PZT layer during sintering. The dielectric properties of the PZT layers printed and fired on the Ni substrates with the prefired Au electrode were significantly better than those of the layers on the uncoated substrate, the dielectric losses decreased from 0.23 to 0.05.

Effect of Electrical Properties and Microstructures of Pb(Zr,Ti)O3 Thick Films Prepared by Aerosol Depoisition on CO2 Laser Radiation

Effect of Electrical Properties and Microstructures of Pb(Zr,Ti)O3 Thick Films Prepared by Aerosol Depoisition on CO2 Laser Radiation

Preparation of Ba(Ti, Zr)O3 Thick Films by Screen Printing

BaTi1-xZrxO3 (x=0–0.1) thick films were prepared by a screen-printing method on Pt bottom electrodes using ceramic substrates in the firing temperature range from 1250°C to 1450°C. The dielectric, ferroelectric and electric-field-induced strain properties of the thick films were examined in comparison with those of bulk ceramics. The optimum firing temperature to obtain maximum remanent polarization was 1400°C for the thick films. The phase transition temperatures were controlled by varying composition x for the thick films as well as the bulk ceramics. The maximum remanent polarization of 14.4 µC/cm2 for the thick film was obtained at x=0.025 in the orthorhombic phase.

Low Temperature Processing of Nanocrystalline Lead Zirconate Titanate (PZT) Thick Films and Ceramics by a Modified Sol-Gel Route

Dispersing fine particles into a sol-gel matrix is a promising process to get a thick 0–3 composite coating layer. In this paper, we have further improved this modified sol-gel process by nanocrystalline composite technique to realize the low temperature annealing. Dense Pb(Zr, Ti)O3 (PZT) thick films of 10 to 50 µm in thickness have been obtained on the platinum-coated silicon substrates by spin-coating at sintering temperature of 600–700°C and fully developed submicron-sized grains have been demonstrated in screen-printing piezoelectric films on alumina substrates at sintering temperature of 700–800°C. The dependence of various properties such as microstructure, crystallization, ferroelectric and dielectric properties of such made thick films on the processing parameters have been investigated. For a 10 µm-thick film spin-coated on silicon wafer, the dielectric loss and relative permittivity are 0.010 and 1024, respectively, at 1 kHz. The remanent polarization (Pr) and the coercive field (Ec) are 13.6 µC/cm2 and 34.5 kV/cm, respectively. Obviously, such made thick film has comparable properties with bulk PZT ceramic. This novel technique can be extensively used in sol-gel, screen-printing, tape-casting, even in traditional ceramic process to reduce the process temperature.

Preparation of Thick Pb(Zr, Ti)O3 (PZT) Film by Electrostatic Spray Deposition (ESD) for Application in Micro-System Technology

A Pb(Zr, Ti)O3 (PZT) thick film was prepared by electrostatic spray deposition (ESD) using a sol-gel solution as the precursor. The steady spray, which is suitable for large area and uniform PZT film deposition, can be achieved at an applied electric potential of 4500 volts and solution flow rate of 0.6 ml/h for the 0.4 M sol-gel PZT solution. The use of 100-nm-thick sol-gel PZT as a buffer layer affected the ESD-deposited PZT film's nucleation and growth behavior and enhanced the PZT (100) orientation. By using sol-gel PZT as the intermediate layer to increase the density of the ESD-deposited PZT film, the relative dielectric constant of as high as 960 can be achieved. Our primary results proved that ESD is a promising method for the preparation of thick PZT films with good piezoelectric properties.