• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.341-342
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• 2006

Gadolinium-substituted bismuth titanate, $Bi_{3.3}Gd_{0.7}Ti_3O_{12}$ (BGT), thin films were successfully fabricated on Pt(111)/Ti/$SiO_2$/Si substrates by a sol-gel method and their structural and ferroelectric properties have been characterized. Fabricated BGT thin films were found to be random orientations, which were confirmed by X-ray diffraction experiment and scanning electron microscope analysis. The remanent polarization ($2P_r$)) of BGT thin film annealed at $720^{\circ}C$ was $25.85\;{\mu}C/cm^2$ at an applied voltage of 5 V. The BGT thin films exhibited a 11 % reduction in their switching charge after no less than $10^{11}$ switching cycles at a frequency of 1 MHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.12-13
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• 2006

Ferroelectric Cerium-substituted $Bi_4Ti_3O_{12}$ thin films with a thickness of 200 nm were deposited using the liquid delivery metal organic chemical vapor deposition process onto a Pt(111)/Ti/$SiO_2$/Si(100) substrate. At annealing temperature above $600^{\circ}C$, the BCT thin films became crystallized and exhibited a polycrystalline structure. The BCT thin film annealed at $720^{\circ}C$ showed a large remanent polarization ($2P_r$) of $44.56\;{\mu}C/cm^2$ at an applied voltage of 5V. The BCT thin film exhibits a good fatigue resistance up to $1{\times}10^{11}$ switching cycles at a frequency of 1 MHz with applied electric field of ${\pm}5\;V$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.290-291
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• 2006

The effect of praseodymium substitution on the ferroelectric properties of $Bi_4Ti_3O_{12}$ thin films have been investigated. Ferroelectric Pr-substituted $Bi_4Ti_3O_{12}$ thin films were fabricated by chemical solution deposition onto Pt/Ti/$SiO_2$/Si substrates. The structure and morphology of the films were analyzed using Xray diffraction, and scanning electron microscopy, respectively. About 200-nm-thick BPT films grown at $720^{\circ}C$ exhibited a polycrystalline structure and showed excellent ferroelectric properties with a remanent polarization ($2P_r$) of $28.21\;{\mu}C/cm^2$ at an applied voltage of 5 V. The films a1so demonstrate fatigue-free behavior up to $10^{11}$ read/write switching cycles with 1 MHz bipolar pulses at an electric field of ${\pm}5\;V$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.382-383
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• 2006

The tungsten bronze type of strontium barium niobate(SBN) thin film was synthesized by metal organic decomposion method for SBN stock solution and the SBN thin film process were deposited by spin-coating process on Pt-deposited si-wafer(100) by magnetron sputtering system. The thickness of SBN thin film was 150~200 nm and were optimized for rpm of spin-coater system. The structural variation of SBN thin film was studied by TG-DTA and XRD. The deposited SBN stock solution on annealing at $400{\sim}800^{\circ}C$ a pure tungsten bronze SBN phase and the corresponding. average grain size about 500~1000 nm influenced by annealing temperature. The piezoelectric properties of prepared SBN thin film, the remanent polarization value(2Pr) and coercive field was $1.2{\mu}C/cm^2$ and 2.15V/cm, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.276-277
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• 2006

1mm-thick BLT ceramics were sintered in accordance with a bulk ceramic fabrication process. AII XRD peaks detected in the sintered ceramics were indexed as the Bi-layered perovskite structure without secondary phases. Density was increased with increasing the sintering temperature up to $1050^{\circ}C$ and the maximum value was about 98% of the theoretical density. The remanent polarization (2Pr) value of BLT ceramic sintered at $1050^{\circ}C$ was approximately $6.5\;{\mu}C/cm^2$ at the applied voltage of 4.5 kV. The calculated electromechanical coupling factor ($k_t$) of it was about 5% and the mechanical quality factor (Qm) was about 2200. From these results, a BLT ceramic target for pulsed laser deposition (PLD) system was successfully fabricated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.171-171
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• 2007

Dysprosium-doped bismuth titanate (BDT) thin films were successfully deposited on Pt(111)/Ti/$SiO_2$/Si(100) substrates by liquid delivery MOCVD process and their structural and ferroelectric properties were characterized. Fabricated BDT thin films were found to be random orientations, which were confirmed by X-ray diffraction experiment and scanning electron microscope analysis. The crystallinity of the BDT films was improved and the average grain size increased as the crystallization temperature increased from 600 to $720^{\circ}C$ at an interval of $40^{\circ}C$. The BDT thin film annealed at $720^{\circ}C$ showed a large remanent polarization (2Pr) of $52.27\;{\mu}C/cm^2$ at an applied voltage of 5V. The BDT thin film exhibits a good fatigue resistance up to $1.0{\times}10^{11}$ switching cycles at a frequency of 1 MHz with applied pulse of ${\pm}5\;V$. These results indicate that the randomly oriented BDT thin film is a promising candidate among ferroelectric materials useti비 in lead-free nonvolatile ferroelectric random access memory applications.

• Journal of the Korean Vacuum Society
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• v.8 no.3A
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• pp.238-244
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• 1999

Pt/SBT/Pt capacitors were fabricated using the MOD-derived $SrBi_{2x}Ta_2O_9$ (SBT) films and their ferroelectic and leakage current characteristics were investigated with post annealing at 400~$800^{\circ}C$. Although the MOD-derived SBT film exhibited the hysteresis loop typical for the leaky film, the well-saturated ferroelectric hysteresis loop could be obtained by post annealing the Pt/SBT/Pt capacitors at $550^{\circ}C$~$800^{\circ}C$. The remanent polarization $2P_r$ of the SBT film exhibited a maximum value of 9.72$\mu\textrm{cm}^2$ with post annealing at $600^{\circ}C$, and then decreased with increasing the post annealing temperature above $600^{\circ}C$. The MOD-derived SBT films exhibited the high leakage current density of ~$10^{-3} \textrm{A/cm}^2$ at 75kV/cm. With post annealing the Pt/SBT/Pt capacitor at 600~$800^{\circ}C$, however, the leakage current density decreased remarkably to less than $10^{-6}\textrm{A/cm}^2$ at 75kV/cm.

• Journal of Ceramic Processing Research
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• v.22 no.2
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• pp.214-220
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• 2021

Heterolayered potassium tantalate niobate(KTN(70/30)/KTN(30/70)) thin films on Pt/Ti/SiO2/Si substrates prepared by the sol-gel process and spin coating method. When sintered at 700 ℃ or higher, the X-ray diffraction intensities of the perovskite phase were greatly increased, and it was observed as the main phase of the KTN heterolayered thin film. As the sintering temperature increased from 650 ℃ to 800 ℃, the average grain size increased from 146nm to 380 nm, and the average thickness of the KTN films coated six times was about 394-441 nm. Dielectric constant and dielectric loss of the KTN film sintered at 750 ℃ and room temperature showed good properties of about 2850 and 0.573, respectively, and all films exhibited the typical dielectric relaxation characteristics. The phase transition temperature of KTN thin film was around 12-13 ℃. Remanent polarization and the coercive field of KTN film sintered at 750 ℃ showed excellent properties of 23.98 μC/cm2 and 35.41 kV/cm, respectively. Adiabatic temperature changes (ΔT) and electrocaloric strength of the KTN films sintered at 750 ℃ at 60 ℃ were 2.67℃ and 0.012 KcmkV-1, respectively.

• Journal of the Korean Ceramic Society
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• v.41 no.5
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• pp.401-405
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• 2004

Undoped SrB $i_2$T $a_2$O$_{9}$, donor-doped Sr$_{0.99}$B $i_2$(Ta$_{0.99}$W$_{0.01}$)$_2$O$_{9}$ and acceptor-doped SrB $i_2$(Ta$_{0.99}$Ti$_{0.01}$)$_2$O$_{8.99$ ceramics were prepared and their microstructure, ferroelectric P-E hysteresis and Curie temperature were investigated. Grain size did not influence P-E hysteresis curve in undoped SrB $i_2$T $a_2$O$_{9}$ ceramics. Donor-Doped Sr$_{0.99}$B $i_2$(Ta$_{0.99}$W$_{0.01}$)$_2$O$_{9}$ ceramics showed more saturated P-E hysteresis curve with larger remanent polarization (P$_{r}$) than undoped SrB $i_2$T $a_2$O$_{9}$ ceramics while acceptor-doped SrB $i_2$(Ta$_{0.99}$Ti$_{0.01}$)$_2$O$_{8.99}$ ceramics led to a pinched P-E hysteresis loop. Larger polarization in donor-doped Sr$_{0.99}$B $i_2$(Ta$_{0.99}$W$_{0.01}$)$_2$O$_{9}$ ceramics resulted from easier domain wall motion by Sr-vacancies.

• Journal of Sensor Science and Technology
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• v.6 no.1
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• pp.56-62
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• 1997

Using a rf-magnetron sputtering method, highly c-axis oriented La modified $PbTiO_{3}$ (PLT) ferroelectric thin films with compositions of $(Pb_{1-x}La_{x})Ti_{1-x/4}O_{3}$, where x=0.05, x=0 and x=0.15, have been obtained on (100)MgO single crystal substrate under conditions of low gas pressure. The degree of c-axis orientation of PLT films decreases with increasing gas pressure and with increasing La contant. These films were characterized by X-ray diffraction and SEM. PLT thin films of x=0.05, 0.1 and 0.15 show a low dielectric constant of 218, 246 and 361 at 1 kHz and remanent polarization(Pr) of $9{\mu}C/cm^{2}$, $8{\mu}C/cm^{2}$ and $7{\mu}C/cm^{2}$.