• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.05a
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• pp.100-103
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• 1993

Ferroelectric lean-titanate thin films were fabricated by sol-gel processing. Sol-gel derived $PbTiO_3$ thin films crystallized into the expected tetragonal perovskite structure when heated to $600^{\circ}C$ and above. The effects of annealing temperature on grain size made with SEM observation are reported. The films heated at $650^{\circ}C$ for 30min showed a square-type hysteresis loop with $P_r$ and $E_c$ of $11.5{\mu}C/cm^2$, 115kV/cm, respectively.

• Journal of the Korean Vacuum Society
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• v.5 no.1
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• pp.62-66
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• 1996

$(Ba_{1-x}Sr_xTiO_3$ (BST) thin films have been grown on Pt-coated MgO by metal -organic chemical vapor deposition. X-ray diffraction results showed that BST films were grown on a Pt/MgO substrate with (100) preferred orientation perpendicular to the surface. The lineawr relationship of P-E curve obtained form hysteresis loop measurement indicated that the BST films had a Curie transitions below room temperature . Films deposited at $900^{\circ}C$ exhibited a smooth and dense microstructure, a dielectric constant of 202, and a dissipation facotr of 0.02 at 100kHz. The leakage current density of the BST films is about $2\times10^{-10} \;A/\textrm{cm}^2$$ at an applied electric field of 0.2 MV/cm. The electrical behavior on the current-voltage characteristics is well explained by the bulk-limited Pool-Frenkel emission.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.12
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• pp.1060-1064
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• 2002

We have studied the effect of crystallization temperature, composition and film thickness, which are the fundamental processing parameters of lead zirconate titanate(PZT) thin film fabrication, in the respect of the piezoelectric properties by our pneumatic loading method(PLM). A great deal of research has been done in the field of characterization for piezoelectric thin films after the first report on the measurement for the piezoelectric coefficient of thin films in 1990. Even though the piezoelectric properties of thin films are very critical factors in the micro-electro mechanical system(MEMS) and thin film sensor devices, a few reports for the piezoelectric characterization are provided for the last decade unlikely the bulk piezoelectric devices. We have found that the piezoelectric properties of thin films are improved as the increase of crystallization temperature up to 750$\^{C}$ and this behavior can be also explained by the analysis of dielectric polarization hysteresis loop, X-ray diffraction and scanning electron microscopy. The effect of Zr/Ti composition has been also studied. This gives us the fact that the maximum piezoelectricity is found near Morphotropic Phase Boundary(MPB) as bulk PZT system does.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.341-344
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• 1999

The effects of post annealing treatments of ferroelectrlclty in PZT(P $b_{1.05}$(Z $r_{0.52}$, $Ti_{0.48}$) $O_3$ thin film deposited on Pt/ $SiO_2$/Si substrate by RF-Magnetron sputtering methode was Investigated. Analyses by RTA(Rapid Thermal Annealing) treatments reveled that the crystallization process strongly depend on the healing temperature. The Perovskite structure with strong PZT (101) plan was obtained by RTA treatments at 75$0^{\circ}C$ With increasing RTA temperature of PZI thin films, the coercive field and remanent Polarization decreased, while saturation polarization( $P_{r}$) was decreased. P-E curves of Pt/PZT/Pt capacitor structures demonstrate typical hysteresiss loops. The measure values of $P_{r}$,. $E_{c}$ and dielectric constants by post annealed at 75$0^{\circ}C$ were 38 $\mu$C/$\textrm{cm}^2$ 35KV/cm and 974, respectively. Switching polarization versus fatigue characteristic showed 12% degradation up to 10$^{7}$ cycles.s.s.s.s.s.s.

• Bulletin of the Korean Chemical Society
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• v.18 no.1
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• pp.56-61
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• 1997

Lead zirconate titanate (PZT) thin fills were deposited onto the Pt/Ti/SiO2/Si substrate by the pulsed laser deposition with the second harmonic wavelength (532 nm) of Nd:YAG laser. In order to determine the optimum conditions for the film deposition, the phase of the films were investigated as functions of ambient oxygen pressure, substrate temperature, and laser fluence. Also the chemical composition analysis was conducted for the PZT films deposited under various ambient oxygen pressure. When the distance between substrate and bulk PZT target is set to 20 mm, the optimum conditions have been determined to be 3 torr of oxygen pressure, 1.5 J/cm2 of laser fluence, and 823-848(±10) K range of substrate temperature. At these conditions, perovskite phase PZT films were obtained on platinized silicon. The chemical composition of the films is very similar to that of PZT bulk target. The physical structure of the deposited films analyzed by scanning electron microscopy shows a columnar morphology perpendicular to the substrate surface. Capacitance-Voltage hysteresis loop measurements show also a typical characteristics of ferroelectric thin film. The dielectric constant is found to be 528 for the 0.48 μm thickness of PZT thin film.

• Journal of the Korean Ceramic Society
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• v.54 no.4
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• pp.323-330
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• 2017

To understand the defect chemistry of multiferroic $BiFeO_3-based$ systems, we synthesized nonstoichiometric $Bi_{1+x}FeO_{3{\pm}{\delta}}$ ceramics by conventional solid-state reaction method and studied their structural, dielectric and high-temperature charge transport properties. Incorporation of an excess amount of $Bi_2O_3$ lowered the Bi deficiency in $BiFeO_3$. Polarization versus electric field (P-E) hysteresis loop and dielectric properties were found to be improved by the $Bi_2O_3$ addition. To better understand the defect effects on the multiferroic properties, the high temperature equilibrium electrical conductivity was measured under various oxygen partial pressures ($pO_2{^{\prime}}s$). The charge transport behavior was also examined through thermopower measurement. It was found that the oxygen vacancies contribute to high ionic conduction, showing $pO_2$ independency, and the electronic carrier is electron (n-type) in air and Ar gas atmospheres.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.6
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• pp.442-448
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• 2021

In this work, the (K_1-xAg_x)(Ta_0.8Nb_0.2)O₃ (x=0.1-0.4) ceramics were fabricated using mixed-oxide method, and their structural and electrical properties were measured. All specimens represented a pseudo cubic structure with the lattice constant of 0.3989 nm. When 0.4 mol of Ag was added, second phases induced from metallic Ag and K₂(Ta,Nb)₆O₁₆ phase were observed. Dielectric constant and dielectric loss of K(Ta_0.8Nb_0.2)O₃ specimen doped with 0.3 mol of Ag were 2,737 and 0.446, respectively. The curie temperature was about -5℃, which does not change with Ag addition. The remanent polarization began to decrease sharply around 12~15℃, and the temperature at which the remanent polarization began to decrease as the applied voltage increased shifted to the high temperature side. The electrocaloric effect (ΔT) and electrocaloric efficiency (ΔT/ΔE) of the (K_0.7Ag_0.3)(Ta_0.8Nb_0.2)O₃ ceramics were 0.01024℃ and 0.01825 KmV^-1, respectively.

• Journal of the Korean Vacuum Society
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• v.11 no.4
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• pp.230-234
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• 2002

Metal-ferroelectric-semiconductor(MFS) capacitors by using rapid thermal annealed $LiNbO_3$/Si structures were successfully fabricated and demonstrated nonvolatile memory operations of the MFS capacitors. The C-V characteristics of MFS capacitors showed a hysteresis loop due to the ferroelectric nature of the $LiNbO_3$thin film. The dielectric constant of the $LiNbO_3$film calculated from the capacitance in the accumulation region in the capacitance-voltage(C-V) curve was about 25. The gate leakage current density of MFS capacitor using a platinum electrode showed the least value of $1{\times}10^{-8}\textrm{A/cm}^2$ order at the electric field of 500 kV/cm. The minimum interface trap density around midgap was estimated to be about $10^{11}/cm^2$.eV. The typical measured remnant polarization(2Pr) value was about 1.2 $\mu\textrm{C/cm}^2$, in an applied electric field of $\pm$ 300 kv/cm. The ferroelectric capacitors showed no polarization degradation up to about $10^{10}$ switching cycles when subjected to symmetric bipolar voltage pulse in the 500 kHz.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.8
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• pp.858-868
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• 1992

0.085Ba(LaS11/2TNbS11/2T)OS13T-0.915Pb(ZrS1yTTiS11-yT)OS13T (0.45$\leq$y$\leq$0.65) transparent electrooptic ceramics were fabricated by two-stage sintering method. The structural, ferroelectric and electrooptic properties were investigated varying composition and second sintering time. Also the possibility of application to electrooptic device was studied. If we increase the PbZrOS13T contents, dielectric constants were increased and Curie temperature was decreased. In the composition of 0.55[mol] PbZrOS13T, electromechanical coupling factor and piezoelectric charge constant were the highest values of 43[%] and 173x10S0-12T[C/N], respectively. Mechanical quality factors were decreased with the increasing PbZrOS13T contents. Light transmittance was increased with wavelength when measured from 300[nm] to 900[nm], and with PbZrOS13T contents in the range of 0.50[mol]-0.65[mol], and had the highest value of 67[%] in the composition of 0.65[mol] PbZrOS13T. From the results of ferroelectric hysteresis loop and transmitted light intensity with electric field, the specimens with compositions of 0.65,0.60,0.55[mol] PbZrOS13T were applicable to electrooptic memory device and those with compositions of 0.50,0.45[mol] PbZrOS13T were applicable to linear electrooptic device.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.609-615
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• 2005

The effects of Zr/Ti concentration ratio in PLZT (10/y/z) thin films prepared by sol-gel method are investigated for the NVFRAM application. As Ti amount of Zr/Ti concentration ratio increases, the dielectric constants at 10 kHz decrease from 550 to 400, while the loss tangents increase from 0.028 to 0.053 and the leakage current densities at 170 kV/cm decrease from $1.64\times10^{-6}$ to $1.26\times10^{-7}\;A/cm^2$. In the results of hysteresis loops measured at $\pm170kV/cm$, the remanent polarization and the coercive field increase from 6.62 to $12.86{\mu}C/cm^2$ and from 32.15 to 56.45 kV/cm, respectively, according to the change from 40/60 to 0/100 in Zr/Ti concentration ratio. Fatigue and retention properties also improve much as the Zr/Ti concentration ratio change from 40/60 to 0/100. After applying $10^9$ square pulses with $\pm5V$, the remanent polarization of the PLZT (10/40/60) thin film decreases $50\%$ from the initial state while that of the PLZT (10/0/100) thin film decreases $28\%$. In the results of retention measurements of 10s s, the remanent polarization of the PLZT (10/0/100) thin film dec.eases only $10\%$ from the initial state, while that of the PLZT (10/40/60) thin film decreases $40\%$.