Chang-Yub Park

Electrical and optical properties of PLZT thin films on ITO coated glass by sol-gel processing

Sol-gel processed PLZT thin films were fabricated on ITO-coated glass substrates with RTA (rapid thermal annealing). The electrical and optical properties such as hysteresis curves, dielectric constant, dielectric loss and optical transmittance of thin films were investigated. The PLZT thin films were crystallized to the perovskite structure by RTA at 750°C for 5 min. As the La percentage was increased, the dielectric constant increased, and that of 9/65/35 PLZT thin film was 1750. The coercive field and remnant polarization decreased with La increase from 33.82 kV/cm to 14.71 kV/cm and from 39.26 μC/cm2 to 9.57 μC/cm2 respectively. As the Zr percentage increased at 2% La, the coercive field decreased from 52.94 kV/cm to 30 kV/cm, but the remnant polarization increased from 22.74 μC/cm2 to 50.75 μC/cm2, and the dielectric constant had a maximum value of 1269 at 2/55/45 composition. The optical transmittance was increased as La percentage increased but was decreased as the annealing temperature increased.

Structural and electrical characteristics of (Pb1−xLax)(Zr0.5Ti0.5)O3 thin film capacitors

Abstract Electrical characteristics associated with crystal structure changes as a function of La content for (Pb 1−x La x )(Zr 0.5 Ti 0.5 )O 3 (PLZT) thin films were investigated for applications in DRAM capacitors. Tetragonality of the PLZT films dramatically decreased with increasing La content. Films with La ≥ 20 at% were found to be cubic. Films with La ≥ 10 at% exhibited broader dielectric peaks, compared with those of bulk ceramics, and behaved as relaxor ferroelectrics. Tetragonal PLZT film with 10 at% La had a dielectric constant maximum of 1330 at room temperature and a charge storage density of ∼18 μC/cm 2 at 5 V. A decrease in the coercive field and remnant polarization with increasing La amount was due to the reduced dipolar response caused by the decreased crystal anisotropy. The effective permittivity values were nearly identical to the measured values for films with La ≥ 14 at%, as a result of minimized remnant polarization with increasing La content. Leakage current densities −8 A/cm 2 were observed for films with La ≥ 14 at%.

Post-annealing in oxygen ambient for (Ba, Sr)TiO3 thin films prepared by pulsed laser deposition

Abstract Structural and electrical properties of (Ba0.6Sr0.4)TiO3 thin films prepared by pulsed laser deposition were investigated to verify influences of post-annealing in oxygen ambient. Increase of post-annealing time in oxygen ambient resulted in not only grain growth but also improvement of crystallinity in BST films. Although the post-annealing in oxygen ambient resulted in the increase of surface roughness, it assisted the dielectric constant increase by eliminating oxygen vacancies. The electrical property enhancement including high dielectric constant and low leakage current density was associated with introducing high pressure of oxygen during the post-annealing.

Multilayer piezoelectric actuator with AgPd internal electrode

Abstract Using 70Ag/30Pd paste as an internal electrode which can be sintered at low temperature and have cost down effect in mass productions, multilayer piezoelectric actuators (MPAs) were fabricated with 75 layers, 30 μm thickness layer, by conventional multilayer capacitor(MLC) techniques. The multilayer piezoelectric actuators had no defects such as diffusions of the internal electrode to ceramic body and shortage of internal electrodes. The MPA did not show the cracks in the ceramics parts and the gapping phenomena in the external electrodes when Ag paste was used as external electrodes. The MPA devices showed a maximum displacement of 4 μm at 100 V dc voltage and kept the maximum displacement constant for 300 s. The MPA showed good matching properties between ceramic bodies and AgPd internal electrodes. We confirmed the possibility of large scale production of the multilayer piezoelectric actuators with superior electrical properties and a cost down effect using 70Ag/30Pd paste as an internal electrode.

Design of monoblock dielectric filter using (PbCa)(FeNbSn)O3 ceramics

The microwave dielectric properties of (Pb1-xCax){(Fe0.5Nb0.5)1-ySny}O3 ceramics (0.4 ≤ x ≤ 0.6, y = 0.05, 0.1) and design of 900 MHz band 2-pole monoblock band pass filter (BPF) have been investigated to fabricate BPF. Single-phase specimens having orthorhombic perovskite structure similar to CaTiO3 could be obtained in the compositions of Pb1-xCax){(Fe0.5Nb0.5)1-ySny}O3 (0.4 ≤ x ≤ 0.6, y = 0.05, 0.1). The substitution of Sn for Fe0.5Nb0.5) significantly increased the quality factor Q and slightly decreased the dielectric constant (ɛr). The temperature coefficient of the resonant frequency of 0 ppm °C−1 was realized at x = 0.55 and y = 0.1. The Q · f0 value and (ɛr) for this composition were found to be 8600 GHz and 86, respectively. A monoblock λ/4 dielectric BPF for 900 MHz band portable telephone terminal is presented. This BPF is a kind of combline filter. Computer-aided design (CAD) was used in the modeling procedure. The equivalent circuit of the monoblock BPF is represented by transmission lines and lumped elements based on Zoe and Zoo. A BPF model was designed for surface mounted device (SMD) types. The simulations of the equivalent circuit and BPF structure have been performed to optimize the filter design. Newly developed Pb0.45Ca0.55){(Fe0.5Nb0.5)0.9Sn0.1}O3 dielectric materials were used for BPF fabrication. Experimental results of the fabricated device were in good agreement with the simulation.

Structural and electrical properties of PLZT films on ITO-coated glass prepared by a sol-gel process

Abstract PLZT films prepared by a sol-gel process were fabricated on indium tin oxide (ITO)-coated glass substrates using rapid thermal annealing (RTA). The films crystallized into the perovskite phase when annealed at 750°C for 5 min. X-ray diffraction (XRD) and Raman spectroscopy results indicate that the morphotropic phase boundary of PLZT films shifts toward the Ti-rich side, in contrast to that of bulk ceramics. A dielectric constant of 1270 for the 2/55/45 composition was the maximum value observed. With increasing Zr content in the 2 mol% La modified films, the coercive field decreased from 52.9 to 30 kV/cm and the remanent polarization increased from 22.7 to 50.6 μC/cm 2 . Optical transmittance increased by increasing optical isotropy as the Zr content increased.

Electrical properties of Pb(Zr0.52 Ti0.48)O3 thin films prepared by SOL-GEL processing

Abstract Thin films of Pb(Zr0.52 Ti0.48)O3 were prepared on Pt/SiO2/Si substrates by sol-gel processing and rapid thermal annealing (RTA). The variations of hysteresis curves of the films with different upper electrode materials were studied. In order to investigate the effects of electrode - film interface on the electrical characteristics of the PZT film, the leakage current of the film was observed. While the PZT films with silver electrodes deposited at the substrate temperature of 150°C showed ferroelectric characteristics, the films with silver electrodes deposited at room temperature showed the decreased remanent polarization and the asymmetric hysteresis curves. The films thicker than 0.5 μm with platinum electrodes exhibited fine squareness on the hysteresis curves. However, 0.28 μm thick PZT films with silver electrodes and with platinum electrodes have the coercive fields of 39 kV/cm and 68 kV/cm, the remanent polarization of 21 μC/cm2 and 20 μC/cm2, and the switching voltages of Vp = 6 V and V...

Structural properties and effect of excess pb on pb(zr0.52ti0.48)o3 thin films prepared by sol-gel processing

Abstract Pb(Zr0.52Ti0.48)03 stock solution prepared by sol-gel processing was spin-coated on Pt/SiO2/Si substrates and annealed by RTA (Rapid Thermal Annealing). The crystal structure and the growth mechanism of the films were proposed based on the observation of crystallization process and microstructure of the films fabricated with different conditions, and the effects of excess Pb addition were studied. Films were crystallized into rhombohedral structure by annealing at 550°C for 60 sec or 600°C for 20 sec. The grain size of the film increased as the annealing temperature increases and the films were grown into columnar structure perpendicular to the substrate. The degradation of electrical properties due to Pb loss during RTA annealing was observed, and the addition of 10 wt% of excess Pb to the stock solution could compensated the Pb loss.

Piezoelectric and dielectric properties of the Pb/sub 1-3/spl times//2/Bi/sub x/[(Ni/sub 1/3/Nb/sub 2/3/)/sub 0.4/(Ti/sub y/Zr/sub 1

In this paper, the structural, dielectric and piezoelectric properties of (Pb/sub 1-2x/3/Bi/sub x/)[(Ni/sub 1/3/Nb/sub 2/3/) (Ti/sub y/Zr/sub 1-y/)]O/sub x/(x=0/spl sim/0.02,y=0.58/spl sim/0.62) system have been investigated with the TiO/sub 2//(TiO/sub 2/+ZrO/sub 2/) ratio and the substitution of Bi/sup +3/. With increasing the substitution of Bi/sup +3/ morphotropic phase boundary shifts from the x=0, y-0.61 composition to the x-0.01, y-0.39 composition, Zr-rich region. The dielectric constant is enhanced with the increase of the Bi/sup +3/ substitution, and show the maximum value of 5032 at the x=0.01, y=0.59 composition. Increasing the substitution of the Bi/sup +3/, the electromechanical coefficients (k/sub p/k/sub 31/) increase up to the substitution of 1.0 mol% Bi/sup +3/ and show the highest value of 0.667, 0.449 at the x=0.01, y=0.59 composition. The piezoelectric constants (d/sub 33/,d/sub 31/) have the highest value of 825, 344 at the x=0.05, y=0.6 composition because of the increase of the dielectric constant and the enhancment of the electromechanical coupling factor due to the transfer of crystal structure to MPB by the substitution of 0.5 mol% Bi/sup +3/, and the magnitude of butterfly-type strain shows the maximum value of 1200(*10/sup -6//spl Delta/l/1) at the same composition.