• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1881-1883
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• 2005

In this study, PZT thin films were fabricated using sol-gel Processing onto $Si/SiO_2/Ti/Pt$ substrates. PZT sol with different Zr/Ti ratio(20/80, 30/70, 40/60, 52/48) were prepared, respectively. The films were fabricated by using the spin-coating method on substrates. The films were heat treated at $450^{\circ}C$, $650^{\circ}C$ by rapid thermal annealing(RTA). The preferred orientation of the PZT thin films were observed by X-ray diffraction(XRD), and Scanning electron microscopy(SEM). All of the resulting PZT thin films were crystallized with perovskite phase. The fine crystallinity of the films were fabricated. Also, we found that the ferroelectric properties from the dielectric constant of the PZT thin films were over 600 degrees, P-E hysteresis constant. And the leakage current densities of films were lower than $10^{-8}\;A/cm^2$. It is concluded that the PZT thin films by sol-gel process to be convinced of application for ferroelectric memory device.

• Journal of Surface Science and Engineering
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• v.54 no.6
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• pp.331-339
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• 2021

Environmental barrier coatings(EBCs) are applied to the SiC/SiC ceramic matrix composites(CMCs) in order to protect CMCs from being corroded with water vapor by combustion gas in gas turbine engines. Ytterbium silicates, such as ytterbium monosilicate and ytterbium disilicate, are ones of the candidate materials for EBCs due to their excellent resistance to water vapor corrosion as well as thermal-expansion match with SiC. In this study, ytterbium silicates are fabricated with 2-step solid-state synthesis targeting ytterbium disilicate. After synthesizing ytterbium monosilicate, the mixtures of ytterbium monosilicate and SiO₂ are heat-treated and densified by using pressureless sintering or hot pressing with a variety of heating conditions. The phase formation, thermal expansion, and oxidation behavior are examined with fabricated specimens. The final densified bodies are found to be composites between ytterbium monosilicate and ytterbium disilicate with different ratios, which results in 4.43 to 6.72×10^-6/K range of coefficients of thermal expansion. The probability of these ytterbium silicates for EBC applications is also discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.305-309
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• 2002

We have successfully fabricated a Metal-Ferroelectric-Insulator-Semiconductor (MFIS) structure using Bi$\sub$4-x/La$\sub$x/Ti$_3$O$\sub$12/ (BLT) ferroelectric thin film and SiO$_2$/Nitride/SiO$_2$ (ONO) stacked buffer layers for single transistor type ferroelectric nonvolatile memory applications. BLT films were deposited on 15 nm-thick ONO buffer layer by sol-gel spin-coating. The dielectric constant and the leakage current density of prepared ONO film were measured to be 5.6 and 1.0 x 10$\^$-8/ A/$\textrm{cm}^2$ at 2MV/cm, respectively, It was interesting to note that the crystallographic orientations of BLT thin films were strongly effected by pre-bake temperatures. X-ray diffraction patterns showed that (117) crystallites were mainly detected in the BLT film if pre-baked below 400$^{\circ}C$. Whereas, for the films pre-baked above 500$^{\circ}C$, the crystallites with preferred c-axis orientation were mainly detected. From the C-V measurement of the MFIS capacitor with c-axis oriented BLT films, the memory window of 0.6 V was obtained at a voltage sweep of ${\pm}$8 V, which evidently reflects the ferroelectric memory effect of a BLT/ONO/Si structure.

• Journal of Ocean Engineering and Technology
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• v.24 no.5
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• pp.67-74
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• 2010

Chromate conversion coating is a coating technique used to passivate aluminum, zinc, cadmium, copper, silver, magnesium, tin, and their alloys to slow corrosion. The process uses various toxic chromium compounds, which may include hexavalent chromium. The industry is developing less toxic alternatives in order to comply with substance restriction legislation, such as RoHS. One alternative is to develop a Cr-free coating solution. In this study, eco-friendly, Cr-free solutions (urethane solution S-700, organic/inorganic solution with Si LRO-317) were used. Test specimens were dried in a drying oven at $190^{\circ}C$ for 3, 5, 7, and 9 minutes. Corrosion resistance was evaluated using a salt spray test for 72 hours. The results show that the optimum corrosion resistance was achieved at $190^{\circ}C$ for five minutes for EGI and three or five minutes for HDGI, respectively. The adhesive properties of the two types of coating solutions were superior regardless of drying time.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.155-157
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• 2008

High velocity oxy-fuel (HVOF) thermal spraying coating has been used widely throughout the last 60 years mainly in defense, aerospace, and power plants. Recently this coating technique is considered as a promising candidate for the replacement of the traditional electrolytic hard chrome plating (EHC) which pollutes the environment and causes lung cancer by toxic hexa-valent $Cr^{6+}$. In this study, two kinds of cermet coatings, WC-CoCr and WC-CrC-Ni, are formed by HVOF spraying. The corrosion and electrochemical properties are evaluated by polarization tests in 3.5 wt% solutions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.187-191
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• 1995

Thin film of the (Pb$\_$1-x/La.sub x/)(Zr$\_$0.25/Ti/Sub 0.48/) O$_3$(x=0~13[at%]) were prepared by Sol - Gel method. Multi-layer PLZT thin films were fabricated by spin-coating on Pt/Ti/SiO$_2$/Si substrate. The crystallinity and microstructure of the films were investigated with the sintering condition. At the sintering temperature of of 600[$^{\circ}C$], the perovskite phase was dominat. PLZT(11/52/48)thin films sintered at 600[$^{\circ}C$], 1[hr] had good dielectric constant (1236), dielectric loss (2.2[%]), remanent polarization (1.38[${\mu}$C/$\textrm{cm}^2$] and coercive field(16.86[ kV/cm]) respectively.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.10a
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• pp.170-173
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• 2006

Ferroelectric $Bi_{3.35}Sm_{0.65}Ti_3O_{12}(BST)$ thin films were deposited on $Pt(111)/Ti/SiO_2/Si(100)$ substrates by a sol-gel spin-coating process. In this experiments, $Bi(TMHD)_3$, $Sm_5(O^iPr)_{13}$, $Ti(O^iPr)_4$ were used as precursors, which were dissolved in 2-methoxyethanol. Thereafter, the thin films with the thickness, of 240nm were annealed from 600 to $720^{\circ}C$ in oxygen atmosphere for 1 hr, and post-annealed in oxygen atmosphere for 1 hr after deposition of Pt electrode to enhance the electrical properties. The remanent polarization and coercive voltage of the BST thin films annealed at $720^{\circ}C$ were $19.48\;{\mu}C/cm^2$ and 3.40 V, respectively, and a fatigue-free characteristics. As a result, Sm-substituted bismuth titanate films with good ferroelectric properties and excellent fatigue resistance are useful candidates for ferroelectric memory applications.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.05a
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• pp.194-197
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• 2006

Lead-free bismuth-layered perovskite ferroelectric europium-substituted $Bi_{4}Ti_{3}O_{12}(BTO)$ thin films have been successfully deposited on Pt/Ti/$SiO_2$/Si substrate by a sol-gel spin-coating process. $Bi(TMHD)_3,\;Eu(THMD)_3,\;Ti(OiPr)_4$ were used as the precursors, which were dissolved in 2-methoxyethanol. The thin films were annealed at various temperatures from $600^{\circ}\;to\;720^{\circ}C$ in oxygen ambient for 1 hr, which was followed by post-annealed for 1 hr after depositing a Pt electrode to enhance the electrical properties. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the crystallinity and surface morphology of layered perovskite phase, respectively. The remanent polarization value of the BET thin films annealed at $720^{\circ}C\;was\;25.95{\mu}C/cm^2$ at an applied voltage of 5 V.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.9
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• pp.631-637
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• 2003

We have evaluated structural and electric, ferroelectric properties of PZT(30/70) thick film prepared by using 1,3-propanediol based sol-gel method on Pt/Ti/SiO$_2$/Si substrates. Rapid thermal annealing (RTA) is used to reduce the thermal stress and final furnace annealing is processed at $650^{\circ}C$. As the results of SEM analysis, we find that we get 350 nm in thickness for one coating and 1 $\mu$m for three times of coating. In the results of C-D analysis at 1 kHz, dielectric constant ($\varepsilon$$_{r}$) and dissipation factor were 886 and 0.03, respectively. C-V curve is shaped as a symmetrical butterfly. Leakage current density at 200 kV/cm is 1.23${\times}$10$^{-5}$ A/cm$^2$ and in the results of hysteresis loops measured at 150 kV/cm, the remnant polarization (P$_{r}$) and the coercive field (E$_{c}$) are 33.8 $\mu$C/cm$^2$ and 56.9 kV/cm, respectively. PZT(30/70) thick film exhibits relatively good ferroelectric, electric properties.s..

• Journal of IKEEE
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• v.22 no.4
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• pp.1226-1229
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• 2018

We investigated the improvement of surface roughness and states after high temperature annealing using reduced-graphene oxide (r-GO) capping layer on ion-implanted 4H-SiC epitaxial layer. The specification of the 4H-SiC wafer grown on n-type $4^{\circ}$ off-axis 4H-SiC was $10{\mu}m$-thick and n-type epitaxial layer with a dose of $1.73{\times}10^{15}cm^{-2}$. The $n^+$ region were formed by multiple nitrogen ion-implantations and r-GO capping layer was produced by spray coating method. AFM measurements revealed that RMS value of the sample capped with r-GO was tenfold decrease compared to the sample without r-GO capping. The improvement of surface states was also verified by the improvement of leakage current level.