• Journal of the Korean Ceramic Society
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• v.31 no.9
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• pp.981-988
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• 1994

Crystallizable glasses with precipitation of celsian were prepared for the purpose of insulating dielectric layers for the devices such as integrated circuit substrates. Crystallization behavior of these glasses were studied by DTA, SEM, XRD analysis and by the measurement of dielectric properties. The base composition of the glass-ceramic consists in weight percent of 30% SiO2, 10% Al2O3, 26% BaO, 10% CaO, 10% ZnO, 8%TiO2 and 6% B2O3. 2-6 wt% Y2O3 were selected as the nucleating agent to promote monoclinic celsian formation. As a result, in barium-rich glasses containing 4~6wt% Y2O3 , monoclinic celsian was developed as major crystalline phase in the temperature range of 850~90$0^{\circ}C$. Also, the dielectric constant and quality factor of these glass-ceramics were about 9 and more than 1000, respectively.

• Journal of the Korean Ceramic Society
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• v.43 no.11 s.294
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• pp.715-723
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• 2006

Perovskite oxide materials are very important for the electronics industry, because they exhibit promising properties. With an interest in the obvious applications, significant effort has been invested in the growth of highly crystalline epitaxial perovskite oxide thin films in our laboratory. And the desired structure of films was formed to achieve excellent properties. $Y_1Ba_2Cu_3O_{7-x}$ (YBCO) superconducting thin films were simultaneously deposited on both sides of 3 inch wafer by inverted cylindrical sputtering. Values of microwave surface resistance R$_2$ (75 K, 145 GHz, 0 T) smaller than 100 m$\Omega$ were reached over the whole area of YBCO thin films by pre-seeded a self-template layer. For implementation of voltage tunable high-quality varactor, A tri-layer structured SrTiO$_3$ (STO) thin films with different tetragonal distortion degree was prepared in order to simultaneously achieve a large relative capacitance change and a small dielectric loss. Highly a-axis textured $Ba_{0.65}Sr_{0.35}TiO_3$ (BST65/35) thin films was grown on Pt/Ti/SiO$_2$/Si substrate for monolithic bolometers by introducing $Ba_{0.65}Sr_{0.35}RuO_3$ (BSR65/35) thin films as buffer layer. With the buffer layer, the leakage current density of BST65/35 thin films were greatly reduced, and the pyroelectric coefficient of $7.6\times10_{-7}$ C $cm^{-2}$ $K^{-1}$ was achieved at 6 V/$\mu$m bias and room temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.235-236
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• 2006

The contact resistance and grain boundary potential barrier of ceramic $BaTiO_3$ PTCR were investigated. The electroless plated Ni, evaporated Al, and Ag paste were chosen as electrode materials of PTCR device for comparison analysis before and after heat treatment. The contact resistance of electrode were measured by electrometer (dc), digital multimeter (dc), and LCR meter (ac). In the case of Al electroded samples, the heat treatment and protective oxide layer had high resistance and effect on the stability of PTCR effect against contact resistance degradation, but the Ag-paste had comparably high contact resistance before heat treatment and decreased after heat treatment with safe. On the other hand, the samples with electroless plated Ni electrode had good properties of contact resistance against aging.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.157-160
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• 2004

Ferroelectric $(Ba_xSr_{1-x})TiO_3$ (BST) thin films have been deposited on (001) MgO single crystals by a pulsed laser deposition (PLD) method. The structure of deposited BST thin films were investigated by an x-ray diffractometer. Calculated c-axis lattice parameters of the BST films exhibit a strong lattice distortion, which was not observed in ceramic BST at room temperature. This lattice distortion of BST has been attributed to strains caused by lattice constant difference between film and substrate, oxygen vacancies in BST film, and thermal expansion difference between film and substrate. Ferroelectric properties at 10 GHz have been measured using a HP 8510C vector network analyzer. Dielectric properties, capacitance tunability and quality factor, of the interdigitaed capacitors fabricated on BST films were calculated from the measured s-parameters. Two distinct behaviors in structural, opitical, and microwave properties of BST films were observed; below and above 200 mTorr of oxygen pressure in the deposition chmber.

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.846-849
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• 2003

Doping effect of various ions in Bi-layered ferroelectric $SrBi_2$$Nb_2$$O_{9}$ (SBN) ceramics was studied. Undoped SBN ceramic and SBN ceramics doped with $Ba^{2＋}$, $Pb^{2＋}$,$ Ca^{2＋}$ , $Bi^{3＋}$ , $La^{3＋}$ , $Ti^{4＋}$ , $Mo^{6＋}$ , and $W^{6＋}$ ions were made by a solid state reaction. Dielectric constants were measured with temperature. Ferroelectric transition temperature decreased with $Pb^{2＋}$ , $Ba^{2＋}$ , $La^{3＋}$ doping, but the transition temperature increased with $Ca^{2＋}$ , $Bi^{3＋}$ , $Ti^{4＋}$, $Mo^{6＋}$ , or$ W^{6＋}$ ionic doping. These results show that the ion size plays an important role in the ferroelectricity of SBN ceramic.

• Journal of the Korean Ceramic Society
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• v.21 no.1
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• pp.60-66
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• 1984

During the metallization in the manufacturing of the ceramic capacitor at the boundary layer between Pd or Pt electrode and $BaTiO_3$-dielectric reactions were analysed. For the study of the reaction Electron Spin Resonance (ESR) Method was used. With the aid of ESR an increased of the concentration of the paramagnetic $Ti^{3+}$-Centers on the metallizing process could be seen. It meaned a reduction effect although the metallization was accomplished under oxidation atmosphere. Therefore it could be regarded as a reaction at the boundary layer. In order to investigate the reaction ad double octahedral model was compared and the increase of the $Ti^{3+}$-concentration was studied.

• Korean Journal of Materials Research
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• v.29 no.2
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• pp.73-78
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• 2019

Lead free $(Ba_{0.7}Ca_{0.3})TiO_3$ thick films with nano-sized grains are prepared using an aerosol deposition (AD) method at room temperature. The crystallinity of the AD thick films is enhanced by a post annealing process. Contrary to the sharp phase transition of bulk ceramics that has been reported, AD films show broad phase transition behaviors due to the nano-sized grains. The polarization-electric hysteresis loop of annealed AD film shows ferroelectric behaviors. With an increase in annealing temperature, the saturation polarization increases because of an increase in crystallinity. However, the remnant polarization and cohesive field are not affected by the annealing temperature. BCT AD thick films annealed at $700^{\circ}C/2h$ have an energy density of $1.84J/cm^3$ and a charge-discharge efficiency of 69.9 %, which is much higher than those of bulk ceramic with the same composition. The higher energy storage properties are likely due to the increase in the breakdown field from a large number of grain boundaries of nano-sized grains.

• The Korean Journal of Ceramics
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• v.6 no.4
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• pp.333-338
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• 2000

$Ba_{0.7}Sr_{0.3}TiO_3$(BST) thin films were deposited simultaneously on various electrodes and buffers by the sputtering technique. When the substrate temperature was varied, the BST thin film on each electrode showed good crystallinity above $550^{\circ}C$ as revealed by X-ray diffraction measurements. The surface morphology, determined by atomic force microscopy, indicated that the roughness of BST thin films on $RuO_2$was substrate dependent. However, BST thin films on Ru electrodes are smoother and showed no substrate dependence, probably because the precursor surface diffusion length was greater than the sinusoidal perturbations of the wavelength.

• The Korean Journal of Ceramics
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• v.2 no.2
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• pp.95-101
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• 1996

Variations of the leakage current behaviors and interface potential barrier $({\Phi}_B)$ of rf-sputter deposited (Ba, Sr)$TiO_3$ (BST) thin films with thicknesses ranging from 20 nm to 150nm are investigated as a function of the thickness and bias voltages. The top and bottom electrodes are dc-sputter-deposited Pt films. ${\Phi}_B$ critically depends on the BST film deposition temperature, postannealing atmosphere and time after the annealing. The postannealing under $N_2$ atmosphere results in a high interface potential barrier height and low leakage current. Maintaining the BST capacitor in air for a long time reduces the ${\Phi}_B$ from about 2.4 eV to 1.6 eV due to the oxidation. ${\Phi}_B$ is not so dependent on the film thickness in this experimental range. The leakage conduction mechanism is very dependent on the BST film thickness; the 20 nm thick film shows tunneling current, 30 and 40 nm thick films show Shottky emission current.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.7
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• pp.567-571
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• 2001

We investigated the structural and electrical properties of Ba(Zr$_{x}$Ti$_{1-x}$ )O$_3$(BZT) thin films with a mole fraction of x=0.2 and a thickness of 150 nm. BZT films were prepared on Pt/SiO$_2$/Si substrate with the various substrate temperature by a RF magnetron sputtering system. When the substrate temperature was above 50$0^{\circ}C$, we obtained multi-crystalline BZT films oriented to (110), (111), and (200) directions. As the substrate temperature increases, the films are crystallized and their dielectric constants become high. C-V characteristic curve of the film deposited at high temperature is more sensitive than that of the film deposited at low temperature. The parameters of the BZT film are as follows; the dielectric constants(dissipation factors) at 1 MHz are 95(0.021), 140(0.024), and 240(0.033) deposited at 400, 500, $600^{\circ}C$, respectively; the leakage currents at 666.7 kV/cm are 5.73, 23.5, and 72.8x10$^{-8}$ A/$\textrm{cm}^2$ fo the films deposited at 400, 500, and 600 $^{\circ}C$, respectively; the leakage currents at 666.7kV/cm are 5.73, 23.5, and 72.8x10$^{-8}$ A/$\textrm{cm}^2$ for the films deposited at 400, 500, $600^{\circ}C$, respectively. The BZT film deposited at 40$0^{\circ}C$ shows stable electrical properties, but dielectric constant for application is a little small.ll.