Raman scattering spectra and ferroelectric properties of epitaxial tetragonal Pb(Zr, Ti)O3 were investigated for polar axis-oriented thin films with various Zr/(Zr + Ti) ratios and by changing the ratios from 0 to 0.50 at different measurement temperatures. The chosen films in the thickness range of 1–2 μm present the advantage of showing small residual strain. The E (TO) modes were successfully isolated using cross-polarization configurations, while A1 (TO) and B1 modes were activated using parallel polarization configurations. Systematic changes in Raman peak positions were observed with changes in the Zr/(Zr + Ti) ratios at different measurement temperatures. It was found in both cases that the tetragonal distortion (c/a-1) and the value of square of spontaneous polarization (Ps2) linearly increased with increasing ω2[A1(1TO)], where a and c are the lattice parameters of a and c-axes. This indicates that monitoring A1(1TO) mode is efficient as a characterization method of ferroelectricity. It can also be used as a novel nondestructive process check or reliability assessment technique during fabrication of microelectromechanical systems (MEMS) using piezoelectric materials.

Perfectly (111)-oriented rhombohedral Pb(Zr, Ti)O3 [PZT] films were successfully grown on (111) CaF2 substrates. These films have the polar-axis perpendicular to the substrate surface without non-180o domains. Well saturated polarization (P) –electric field (E) hysteresis loops were observed at various frequencies and temperatures. Temperature dependence of the saturation polarization (Psat.) was in good agreement with the estimated one by Haun et al. using phenomenological approach but did not strongly depend on the measured frequencies. On the other hand, the coercive field (Ec) increased with decreasing temperature and with increasing the measurement frequency.

To achieve ultrasonic transducers operating above 100 MHz, square pillar shaped Pb1.1(Zr0.53Ti0.47)O3 thick film structures were fabricated using a chemical solution deposition (CSD) process. The fabricated sample showed well-saturated P-E hysteresis curve and butterfly-shaped longitudinal displacement curve. The fabricated samples generated more than 100 MHz ultrasonic waves with a pulser/receiver. Electrical impedance properties of the samples were measured with an impedance analyzer. A number of spurious resonant modes were observed in the frequency range from 40 to 300 MHz. The characteristics of the sample were investigated by finite element method (FEM). The FEM simulations were in good agreement with the experimental results. For free-standing (substrate free) 10-μm-thick PZT film models, the resonant frequency of the thickness vibration mode was estimated to be 160 MHz with the FEM simulations. These results indicate that the substrate affects the behavior of the spurious resonant modes. Therefore, a sample structure was designed using the FEM simulation. The FEM result suggests that the backside of the substrate should be removed to reduce the substrate effects. Consequently, the thickness vibration mode was observed clearly at 160 MHz. This structure is applicable to the micromachined ultrasonic transducers (MUT) operating in the thickness vibration mode above 100 MHz.

The actual transverse and longitudinal displacement of PZT thick film was measured using a newly developed atomic force microscopy (AFM). The AFM is attached a feedback circuit named “torsion feedback”. The torsion and Z-height feedback circuits control an AFM cantilever to follow piezoelectric deformation of the sample. To measure transverse displacement, the cantilever contacts the edge of sample. The transverse displacement is determined from the torsion feedback signal absolutely. To measure longitudinal displacement, the cantilever contacts the center of sample. The longitudinal displacement is determined from Z-height feedback signal absolutely. A 5-μm-thick PZT film was prepared on Pt/Ti/SiO2/Si substrates. The film sample was shaped square pillar. The side electrode length (L) of square pillar shaped sample was ranged from 1000 μm to 10 μm. The relation between side electrode length and the transverse or the longitudinal displacements were investigated. With decreasing L, the transverse displacement decreased nonlinearly, and the longitudinal displacement increased nonlinearly. The finite element method (FEM) simulation suggests that the substrate clamped PZT film behaved nonlinearly. The effective -d31 and d33 were calculated from the measured displacement, and these values increase with decreasing L. The effective d33 and -d31 showed correlation, and the ratio was d33 : -d31 = 5.3 : 1 , whereas the bulk ratiois d33 : -d31 = 2.4 : 1.This result suggests that the substrate clamping effect of the transverse displacement was larger than that of the longitudinal displacement.

La doped lead zirconate titanate (PLZT) films are prepared using a chemical solution deposition process. The effect of La substitution on the piezoelectric response was investigated to clear the possibility of the micro actuator application for the PLZT films. Nominal compositions of the 10% Pb excess PLZT precursor solutions were controlled like La/Zr/Ti= 0/65/35, 3/65/35, 6/65/35, and 9/65/35. These precursor solutions were deposited on the Ir/Ti/SiO2/Si substrates, and the thickness of the PLZT films was 2μm. 10 to 20- μm- diameter Pt top electrodes are formed with a sputtering and a photolithography process. The polarization- field (P-E) hysteresis curves and the longitudinal displacement curves were measured with a twin beam laser interferometer connected with a ferroelectric test system. With increasing La substitution amount, the P-E hysteresis curves became slim shape, and remnant polarization (Pr) decreased. The hysteresis of the piezoelectric longitudinal displacement curves also decreased with increasing La substitution amount. The amount of the displacement under unipolar electric field showed a peak at La/Zr/Ti= 3/65/35. The calculated effective longitudinal piezoelectric constant (d33eff) is 129.2 pm/V at 3/65/35. This amount was relatively higher than that of PZT films at morphotropic phase boundary (MPB: 0/53/47) composition prepared the same film preparation process.

Mixed conductive oxides are a topic of interest for applications in oxygen separation membranes as well as use in producing hydrogen fuel through the partial oxidation of methane. The oxygen flux through the membranes is governed both by the oxygen ionic conductivity as well as the material's electronic conductivity; composite membranes like Ce0.8Gd0.2O2-δ(CGO)-CoFe2O4 (CFO) use gadolinium doped ceria oxides as the ionic conducting material combined with cobalt iron spinel which serves as the electronic conductor. In this study we employ ˜ 50 nm sputtered CeO2 layers on the surface of porous CGO ceramic substrates which serve as solution ‘blocking’ layers during the thin film fabrication process facilitating the control of film thickness. Films with thickness of ˜ 2 and 4 microns were prepared by depositing 40 and 95 separate sol-gel layers respectively. Oxygen flux measurements indicated that the permeation increased with decreasing membrane thickness; thin film membrane with thickness on the micron level showed flux values an order of magnitude greater (0.03μmol/cm2 s) at 800oC as compared to 1mm thick bulk ceramic membranes (0.003 μmol/cm2).

We grew the epitaxial Pb(Zr1-xTix)O3 [PZT] and (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 [PMN-PT] films, above 2 μm in thickness, on (100)cSrRuO3//(100)SrTiO3 substrates by metalorganic chemical vapor deposition (MOCVD). PbTiO3 content (x) dependencies of the crystal structure, dielectric and piezoelectric properties were systematically investigated for these films. The constituent phase changed from a rhombohedral (pseudocubic) single phase, a mixture phase of rhombohedral (pseudocubic) and tetragonal phases, and a tetragonal single phase with increasing x for both of PZT and PMN-PT films. The mixture phase region was observed when x=0.40−0.60 for PZT films and x=0.40−0.55 for PMN-PT films, which became wider than that reported ones for PZT sintered bodies and PMN-PT single crystals. In addition, x value moves to the higher one than that reported for the single crystal and/or the sintered body in case of PMN-PT films, while was almost the same in case of PZT films. The dependence of relative dielectric constant εr was maximum at the mixed phase region for both films, which were similar to the case of their bulk materials. The higher value of εr was ascertained for the PMN-PT films compared with PZT films, however, the magnitude was lower than the reported one for bulk materials. The longitudinal electric-field-induced strain Δx33 and transverse piezoelectric coefficient e31,f for PZT films were also maximum at the mixed phase region, on the other hand, that for PMN-PT films were maximum at larger x edge of rhombohedral (pseudocubic) region. Almost the same order of Δx33 was observed under applied electric fields up to 100 kV/cm, while larger e31,f was observed in PMN-PT films compared with the case of PZT films. e31,f coefficients of ∼−8.9 C/m2 and ∼−11.0 C/m2 were calculated for the PZT film with x=0.46 and for the PMN-PT film with x=0.39, respectively.

Micro-machined piezoelectric film devices are usually fabricated onto substrates, so that the displacement response of the film is clamped with the substrate. To investigate the longitudinal displacement behavior of 10-μm-thick lead zirconate titanate (PZT) films deposited onto Si substrates, disk shape structures with diameters of 20 to 80-μm were fabricated by an reactive ion etching (RIE) process. The polarization-field (P-E) hysteresis curves did not show a remarkable difference with decreasing the PZT disk diameter. On the other hand, unipolar driven longitudinal displacement increased, and the amount of the displacement was saturated at a diameter of 30 and 20 μm. The AFM measured longitudinal piezoelectric constants, AFM d33, were estimated in the case of before poling and after poling at 100V for 10 min. The AFM d33 for the before and after poling process were 65 and 94 pm/V for 80-μm-diameter film disk, and 153 and 315 pm/V for 20-μm-diameter film disk, respectively. The value of poled AFM d33 for 20-μm-diameter film disk was comparable to bulk PZT ceramics. These results suggest that the decrease of the disk diameter reduces the Si substrate bending related with the clamping effect between the film and substrate, and facilitates domain reorientation in the poling process. It seems that the actual piezoelectric constant of films can be estimated from the longitudinal displacement when the ratio of the PZT disk diameter, d, to the PZT film thickness, t, shows d/t < 3 for 10-μm-thick PZT films.

Electric-field-induced displacements of PZT film capacitor Pt/PZT/Pt/SiO2/Si(100) were calculated by finite element method (FEM) with changing all piezoelectric and elastic constants of PZT so as to discuss how to evaluate intrinsic d33 of piezoelectric thin films. Two kinds of conditions, namely, “ideal conditions” and “second-best conditions” are discussed. The ideal conditions indicate that the diameter of top electrode φTE is equal to or less than PZT film thickness tPZT and continuous PZT is etched to isolate the capacitor from the continuous piezoelectric film layer. Under the ideal conditions, d33 measured by atomic force microscopy (AFM) and double beam interferometry (DBI) were the same value that was equal to intrinsic d33 of PZT and was independent of other material constants. Under the second-best conditions, i.e. 20×tPZT < φTE for DBI and 20×tPZT < φTE < 0.5×(tsub: substrate thickness) for AFM, measured d33 depended on only d31, s11, s12 and s13, and obeyed the Lefki's equation qualitatively. However, quantitative differences between FEM analysis and the Lefki's equation were not negligible.

This study is about new plasma deposition method fabricating piezoelectric films applied for actuators in MEMS devices.

Ion-beam-assisted deposition (IBAD) has been used to prepare biaxially textured templates necessary to realizing high superconducting performance in coated conductors.The IBAD method is characterized by the direct deposition of sharply aligned templates on nontextured metal substrates using fluorite-like oxide films (yttrium-stabilized zirconia, Gd2Zr2O7, etc.).Recent progress in vacuum technology for IBAD has made it possible to reproducibly fabricate long lengths (100 m) of IBAD-GZO templates.Continuous deposition of YBCO films on these templates has been achieved by pulsed laser deposition (PLD).Furthermore, a new approach to improving the texture of IBAD templates was found by using CeO2 films grown by PLD.Trifluoroacetate-based metalorganic deposition has also been used instead of PLD to produce superconducting layers on IBAD buffered tapes, aiming at a low-cost process.This article reviews progress in the research and development of biaxially textured templates produced using IBAD and their subsequent use in fabricating superconducting tapes and wires by means of several processes.

Ce0.8Gd0.2O1.9 (CGO) - MFe2O4 (M=divalent cation) is a composite-type oxygen-ionic and electronic mixed conductor. Dense nanocrysalline CGO-CoFe2O4 thin films with a thickness of approximately 1 μm were prepared on CGO porous substrates by a chemical solution spin-coating method. The oxygen permeable flux of the thin film was investigated in temperature range of 700°C - 800°C without physical leak of N2 gas. The permeable flux depends on the measuring time, when the measuring temperature was kept at 750°C before increasing to 800°C. This fact suggests that the O2 permeable properties were affected by a slight change of the film morphology and the crystallinity.

Ti-site substitution using the higher-valent cation was performed on ferroelectric thin films of neodymium-substituted bismuth titanate, (Bi,Nd)4Ti3O12 (BNT), in order to improve its ferroelectric properties by compensating the space charge in BIT-based crystal. Ti-site-substituted BNT films, (Bi3.50Nd0.50)1-(x/12)(Ti3.00-xVx)O15 (x = 0 ∼ 0.09), were fabricated on (111)Pt/Ti/ SiO2/(100)Si substrates using a chemical solution deposition (CSD) technique. V5+-substitution enhanced the remanent polarization of BNT film without change in the coercive field. V5+-substitution also exhibited the possibilities for improving the endurance against leakage current and fatigue degradation.

To reveal the complete performance of intrinsic ferroelectriciy-related properties in single crystalline bismuth-layer-structured displacive ferroelectrics in film form on Si, the crucial roles of both orientation control technology by lattice matching from the atomic arrangement of substrate layer and configuration of the volume fraction of 90°-domain during cooling process were demonstrated. 1.2 μm-thick and Pr3+-substituted Bi4-xPrxTi3O12 (BPT, x =0.0, 0.3, 0.5, 0.7) films were grown on Ir(111)/Ti/SiO2/Si(001) substrates by chemical solution deposition (CSD) method with preferred orientation along the major component of Ps vector. BPT film of x =0.3 exhibited superb ferroelectric properties of remanent polarization 2Pr=92 μC/cm2, saturation polarization Psat=50 μC/cm2, and coercive field 2Ec=184 kV/cm. The film also showed uniform piezoelectric response with an effective piezoelectric coefficient of AFM-d33=36 pm/V. During the decomposition of precursor solutions, IrO2 layers were formed at the surface of Ir layers and promoted a/b-axes orientation. During the cooling process after grain growth, in addition, the differential thermal expansion and residual strain between film and substrate introduced bidirectional lateral stress into BPT film and might eliminate the 90°-domain walls dividing a-and b-domains through the relaxation by domain formation at the Curie temperature TC. Consequently the polar-axis orientation was distinctively grown along the film normal and the conjugate non-polar-axis was grown in-plane.

A combination of the preparation techniques for the ferroelectric films and the micro machining of Si is considered to be an effective way to fabricate microelectromechanical systems (MEMS), such as piezoelectric micro-transducer devices for the electrical and medical fields. In this study, 10-μm-thick disk shape lead zirconate titanate (PZT) thick films were successfully fabricated using a chemical solution deposition (CSD) process. Pt top electrode and PZT layer were etched by reactive ion etching (RIE) process, and 100 to 500-μm-diameter PZT micro disks were fabricated on Pt/SiO2/Si substrate. The relative dielectric constant, dissipation factor, remnant polarization and coercive field were εr = 1130, tanδ = 0.02, Pr = 14 μC/cm2 and Ec = 25 kV/cm, respectively. This means that the ferroelectric and dielectric properties of the PZT micro disks were comparable with that of the bulk PZT ceramics. The PZT micro disk showed the butterfly-shaped displacement curve, related with piezoelectric response, in the case of bipolar measurement. The piezoelectric constant of the PZT disks poled at 80Vfor 10 min was estimated to be AFM d33 = 221 pm/V. A resonance frequency of the radial oscillation was evaluated to apply for micro transducer devices.

Electric-field-induced displacements of PZT film capacitor Pt/PZT(5μm)/Pt/SiO2/Si(100) were calculated by finite element method with various parameters of sample geometry: the diameter of top electrode φ TE ranging from 0.2 μ m to 1000 μ m and whether PZT film was continuous or side-etched. If φ TE was larger than 40μ m, surface longitudinal displacement (corresponding to AFM-measured strain) was not equal to net longitudinal displacement of PZT film, including a contribution of the bending motion of substrate. In contrast, if φ TE was smaller than 4μ m and PZT film was continuous, effective d33 evaluated from net longitudinal displacement was smaller than intrinsic d33, because the side PZT film clamped the edge of the capacitor disk and prevented the whole disk from elongating longitudinally. It was also revealed that d33 value calculated from net longitudinal displacement of PZT film depended on the Poisson's ratio of PZT and was not equal to intrinsic d33, excluding the case that φ TE was smaller than 4μ m and PZT film was side-etched. In conclusion, it is suggested that smaller φ TE (< 4μ m, in our case) and side-etch treatment permit a precision measurement of d33; however this condition is difficult to be satisfied experimentally.

This work presents the preliminary experimental results of Pb(ZrxTi1−x)O3 (PZT) thin films preparation to develop a new combinatorial process by chemical solution deposition (CSD) method. PZT thin films were fabricated from the PbZrO3 (PZ) and PbTiO3 (PT) multilayers on a substrate of Si/SiO2/Ti/Pt. The precursor PT and PZ solutions were coated in different sequences, (i) in the PT start sequence and (ii) in the PZ start sequence, and with different PT and PZ concentrations. It was found that the deposition sequence of PT and PZ led to the differences in composition, microstructure, texture, and ferroelectric property of the resultant thin films. The PT start deposition was suitable for preparation of the PZT thin films, while the PZ start deposition caused composition deviation and bad ferroelectric property. The postannealing had little effect for the formation of the PZT thin films from the multi-PT and PZ layers. A single perovskite phase of PZT can be obtained from the deposited multi-PT and PZ layers even without any postannealing when concentrations of the precursor PT and PZ solution are smaller than 0.025 M and the deposition sequence is in the PT start sequence. This method would be a constructive way to develop and study other thin film materials systems.

Strongly (117)-oriented Bi4Ti3O12 (BIT) thin (300 nm in thickness) and thick (900 nm in thickness) films were successfully synthesized from chemical solution and the piezoelectric and ferrelectric properties were studied. The chemical solution of Bi-acetate and Ti-iso-propoxide dissolved in 2-methoxyethanol was spin-coated on Pt(111)/Ti/SiO2/Si(001) substrate, pyrolysed at 450–600 °C and annealed at 600 °C. On 300-nm-thick BIT thin film, Pt top electrodes were deposited through a metal mask by RF-sputtering. For longitudinal piezoelectric displacement measurement in partially unconstraint, 900-nm-thick BIT thick film, an array of disk-shape BIT capacitor cells with Pt top electrode layers standing on the Pt bottom electrode were fabricated by photolithography with the diameter of 80, 50, 30, 20 μm. To recover from plasma damage, post deposition annealing of 300-nm-thick BIT film and post lithograph annealing of 900-nm-thick BIT film were performed, respectively. Longitudinal piezoelectric displacement was measured directly from the Z-feedback and Z-error signals of an AFM piezoscanner head with application of ac electric field at 5 Hz and 1 kHz, respectively between the conductive cantilever tip contacted to the top Pt electrode and the bottom Pt electrode. By the removal of sidewalls of BIT, positive piezoelectric displacement response was measured. The maximum strain was about 0.1 % under bipolar drive (amplitude of 400 kV/cm or 4Ec). From the unipolar driven piezoelectric displacement, piezoelectric coefficient AFM-d33 was measured. The value of AFM-d33 increased to decreasing cell diameter and approached to a somewhat constant value of 12–13 pC/N. Considering the crystalline orientation, this value well corresponds to that of 20 pC/N which were reported previously in single crystal. The result of ferroelectric property measurement was rather contradictory. The values of remanent and saturated polarization Pr=20 and Psat=28 μC/cm2, respectively measured in 300-nm-thick BIT thin film were in good agreement with reported spontaneous polarization Ps=50 μC/cm2 along a-axis with the consideration of measured inclination angle of Ψ=58° between (200) and (117). In 900-nm-thick BIT thick film, on the other hand, measured values of Pr=6–7 μC/cm2 were much poorer than those of the thin film even with the consideration that measurement frequencies were 1 kHz in the thick film and 50 Hz in the thin film, although the films showed (117)-orientation. Measured piezoelectric response may reflect a specific single grain with favorable orientation in a cell, on the other hand, average value of ferroelectric property throughout a cell in the 900-nm-thick BIT thick film having mixed orientation of (117) and (020).

Bismuth titanate (Bi4Ti3O12; BIT) -based ferroelectric thin films fabricated from a view point of “the site-engineering technique” have been expected to improve the fatal disadvantage of a ferroelectric BIT film, i.e., its low spontaneous polarization; here, Bi- and Ti-site ions in the BIT crystal are cosubstituted by lanthanoid ions and cations with a higher charge valence, respectively, In the present study, we have mainly focused on Ti-site substitution of bismuth titanate (Bi4Ti3O12; BIT)-based thin films using some ions with higher charge valences (V5+, Nb5+, Ta 5+ and W6+; in this study) to enhance the ferroelectric properties of those materials. The BIT-based films with various chemical compositions were fabricated on a (111)Pt/Ti/SiO2/(100)Si substrate by a chemical solution deposition method.

Ti-site substitution of BIT films by the higher-valent ions, Bi3.99(Ti2.97V0.03)O12, Bi3.99(Ti2.97Nb0.03)O12, Bi3.99(Ti2.97Ta0.03)O12 and Bi3.98(Ti2.97W0.03)O12, reduced the leakage current density of BIT films from ∼ 10-6 down to ∼ 10-7 A/cm2 at an applied field of 50 kV/cm, while the substitution by the same-valent cation, e.g., Bi4.00(Ti2.97Zr0.03)O12, did not affect the behavior of leakage current. Whereas polarization (P) - electrical field (E) hysteresis loops of non-substituted and Zr-substituted BIT films were distorted due to the leakage current, non-distorted P-E loops were obtained at V5+-, Nb5+-, Ta5+- and W6+-substituted BIT films.

Also, Ti-site substitution was effective for improving the ferroelectric properties in lanthanoid-substituted BIT films. In the case of La3+-substituted BIT film (BLT), remanent polarization (Pr) of V5+- and W6+-substituted BLT films, (Bi3.24La0.75)(Ti2.97V0.03)O12 and (Bi3.23La0.75)(Ti2.97W0.03)O12 (13 and 12 μC/cm2, respectively), were larger than those of Zr4+- and non-substituted BLT films, (Bi3.25La0.75)(Ti2.97Zr0.03)O12 and (Bi3.25La0.75)(Ti3.00)O12 (8 and 9 μC/cm2, respectively), while those films had similar coercive field (Ec) of approximately 120 kV/cm. Also in the case of Nd3+-substituted BIT film (BNT), Pr and Ec values of V5+-substituted BNT film, (Bi3.24Nd0.75)(Ti2.98V0.02)O12, were 37 μC/cm2 and 119 kV/cm, respectively, which were comparable with those of conventional Pb-based ferroelectrics such as lead zirconate titanate, Pb(Zr,Ti)O3. We concluded that enhancement of the Pr value was achieved by the charge compensation of oxygen vacancies in BIT-based ferroelectrics using higher-valent cations than Ti4+ ion whereas no obvious differences were found in the crystal orientation and or microstructure of these films.