Chang Jung Kim

Electrical characteristics of (100), (111), and randomly aligned lead zirconate titanate thin films

(100), (111), and randomly aligned lead zirconate titanate thin films on Pt/Ti/Corning 7059 glass substrates were prepared using a sol‐gel method. The thin films, having different alignments, were fabricated by different drying conditions for pyrolysis. The hysteresis loop and the capacitance‐voltage characteristics were investigated using a standardized ferroelectric test system. The dielectric constant and the current‐voltage characteristics of the films were investigated using an impedance analyzer and a pA meter, respectively. The microstructure was investigated using scanning electron microscopy. The (100) aligned film showed a relatively larger dielectric constant than the (111) and the randomly aligned films. The films aligned in particular directions showed higher hysteresis parameters than the randomly aligned film. The leakage current densities of the films aligned in particular directions were lower than that of the randomly aligned film.

Epitaxial growth of sol-gel PLZT thin films

Epitaxial lead lanthanum zirconate titanate [PLZT(9/50/50)] thin films were fabricated on various single crystal substrates using the spin coating of metallo-organic solutions. The films were heat-treated at 700 °C for 1 h using the direct insertion method. The films were epitaxially grown with (100), (100), and (110) being parallel to the SrTiO 3 (100), the MgO(100), and the sapphire (01 1 2) substrates, respectively. The epitaxy of the films was investigated using x-ray diffraction, pole figures, rocking curves, and scanning electron microscopy.

Investigation of the drying temperature dependence of the orientation in sol–gel processed PZT thin films

The crystal orientations of lead zirconate titanate (PZT) thin films have been investigated by using various drying temperatures in the sol–gel process. The films were dried at different temperatures between 310 and 350°C for pyrolysis and then were heat treated at 650°C using rapid thermal annealing (RTA). TG/DTA and FTIR spectroscopy were used to detect the remnants of organic materials in the thin films prior to the final heat treatment. In order to examine the relationship between the film orientation and the remaining organic materials for the prior and final heat treatment, the films were fabricated with different coating cycles and dried for different holding times and then annealed at 650°C. The preferred orientations were investigated using X-ray diffraction.

Effects of substrate and bottom electrodes on the phase formation of lead zirconate titanate thin films prepared by the sol-gel method

Lead zirconate titanate (PZT) thin films were fabricated using sol-gel spinning onto Pt/glass, Pt/Ti/glass and Pt/Ti/SiO2/Si substrates and heat-treated using rapid thermal annealing (RTA). The preferred orientation and the perovskite phase content of the PZT thin films were studied using X-ray diffraction analysis (XRD), and the polarization vs electric field (P-E) hysteresis characteristics were investigated using a standardized ferroelectric test system. All of the resulting films on platinized substrate with Ti adhesion layer were well crystallized with the perovskite phase. A preferred (111) orientation was obtained on the Pt/Ti/glass substrate. The saturation polarization of the PZT film on glass substrates was higher than that on Si substrates.

Effects of Seeding Layer on Perovskite Transformation, Microstructure and Transmittance of Sol-Gel-Processed Lanthanum-Modified Lead Zirconate Titanate Films

A series of sol-gel-processed lanthanum-modified lead zirconate titanate (PLZT) thin films with La/Zr/Ti ratios of 8.5/65/35, 9/65/35, 9.5/65/35, 15.5/40/60 and 18/30/70 were prepared on indium tin oxide (ITO)-coated Corning 7059 glass substrates and heat-treated at different temperatures from 475° C to 685° C. The X-ray diffraction, microstructure, optical transmittance spectra and the polarization vs electric field curves were investigated. The P(L)ZT thin films of higher Ti/Zr ratio show lower transformation (from pyrochlore to perovskite) temperature. The PLZT(8.5–9.5/65/35) thin film with the seeding layer shows improved phase content, high optical transmittance and enhanced perovskite transformation kinetics. The grain sizes are reduced (from 5–6 µ m to 0.1–0.2 µ m) and uniform. The fracture surfaces of the films with a seeding layer consist of columnar structure of which the grains grew from the seeding layer. The optical transmittance is enhanced, and the polarization value at 400 KV/cm increases for the film with the seeding layer.

Ferroelectric properties of bismuth titanate niobate Bi7Ti4NbO21 thin film

Abstract The ferroelectric properties of the bismuth titanate niobate Bi 7 Ti 4 NbO 21 thin film have been studied. The Bi 7 Ti 4 NbO 21 thin film was successfully fabricated on platinized Si substrates by chemical solution deposition method. The crystallization of bismuth titanate niobate thin film was observed using an X-ray diffraction analysis (XRD). The hysteresis loop was observed a standardized ferroelectric test system. The thin film exhibits ferroelectric hysteresis with remnant polarization P r =5.65 μC/cm 2 and coercive field E c =127 kV/cm.

Control of preferred orientation in sol-gel lead-zirconate-titanate film on Pt/Ti/glass substrate

The method for controlling the crystal orientation of lead-zirconate-titanate (PZT) thin films has been studied. The PZT thin films were fabricated using sol-gel spin-coating onto Pt/Ti/glass substrates. As the films were heat treated at different temperatures between 270 and 350°C for pyrolysis, we may control the crystal orientations. The firing for the crystallization was done at 650°C using rapid thermal annealing (RTA). The preferred orientation of the PZT thin films was observed using X-ray diffraction analysis (XRD), rocking curves, pole figures, and the microstructure was investigated using scanning electron microscopy (SEM). The preferred orientations in the direction of the (111) plane and (100) plane were obtained using the heat treatment for pyrolysis at 330°C and 350°C, respectively.

A study on the microstructure of preferred orientation of lead zirconate titanate (PZT) thin films

The lead zirconate titanate (PZT) thin films were fabricated using sol-gel spin coating onto PtyTiyglass substrates. Effects of the holding time for pyrolysis and the coating cycle on the preferred orientation of the PZT thin films were studied. The films were fabricated with different coating cycles (3, 5, 7, 9, 11), dried at 330 ±C for different holding times (5, 30, 60 min), and then annealed at the same temperature of 650 ±C using rapid thermal annealing (RTA). The preferred orientations of the films were investigated using x-ray diffraction and glancing angle x-ray diffraction. The microstructure and the selected area diffraction pattern of the PZT thin films were also investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively.

Effects of Seeding Layer on Orientation and Phase Formation of Sol-Gel-Derived Lanthanum-Modified Lead Zirconate Titanate Films on Glass

Sol-gel-derived lanthanum-modified lead zirconate titanate (PLZT) thin films with La/Zr/Ti ratios of 9.5/65/35, 15.5/40/60 and 18/30/70 were prepared on Corning 7059 glass substrates using a seeding layer [PLZT(14/0/100)]. The X-ray diffraction patterns and the microstructures of the films were investigated. The PLZT(9.5/65/35) thin films without the seeding layer consisted of both pyrochlore and amorphous phases. However the PLZT(9.5/65/35) thin films with the seeding layer showed preferred orientation as well as higher perovskite phase content. The orientation of the film varied with the thickness and the heat treatment of the seeding layer. The results will be discussed in terms of the effects of the seeding layer on the orientation and the content of the perovskite phase of the PLZT thin films on glass substrates.

Impedance analyses of cooling-rate effects on the depletion layer of PTCR materials

Cooling-rate effects on the depletion layer of BaTiO3 positive temperature coefficient of resistance (PTCR) were analysed using d.c. resistivity and a.c. complex impedance spectroscopy. As the cooling rates decreased, the d.c. resistivity of the sample increased. A.c. complex impedance spectra showed that the observed d.c. resistivity increase was mainly due to the grain-boundary resistivity increase. The grain resistivity also exhibited relatively weak PTCR behaviour. The built-in potential and the depletion-layer width were analysed using the a.c. complex impedance data. Slow cooling rate produced higher built-in potential and large depletion-layer width. The relationship between the built-in potential and the depletion-layer width at different temperatures was analysed and used to explain the observed grain-boundary resistivity change. The resistivity decrease in the low-temperature region was due to the depletion-layer width decrease. The resistivity jump over the temperature was due to both the built-in potential and the depletion-layer width changes.