• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.273-278
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• 2000

In order to study effects of interface layers between PZT films and electrodes for MFM(Metal-Ferroelectric-Metal) structure capacitors, we have fabricated the capacitors with the Pt/PZT/interface-layer/Pt/$TiO_2/SiO_2/Si$ structure. $PT(PbTiO_3)$ interface layers were formed by sol-gel deposition and PbO, $ZrO_2$ and $TiO_2$ thin layers were deposited by reactive sputtering. $TiO_2$ interface layers result in the finest grains of PZT films compared to $PbO_2$ and $ZrO_2$ layers. On the other hand, PT interface layers result in improved morphology of PZT films and do not significantly change ferroelectric properties. It is also observed that seed layers at the middle and top of PZT films do not give significant effects on grain size but the PT seed layer at the interface between the bottom electrode and the PZT films results in the small grain size.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.509-512
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• 1999

Ferroelectric Sr$_2$(Nb, Ta)$_2$O$_{7}$(SNTO), La$_2$Ti$_2$O$_{7}$(LTO) thin films were prepared by sol-gel processes. SNTO, LTO thin films were spin-coated on Pt/TiO$_2$/SiO$_2$/Si(100). Pt/Ti/SiO$_2$/Si(100). PT/ZrO$_2$/SiO$_2$/Si(100) substrates. After multiple coating, dried thin films were heat-treated for decomposition of residual organics and crystallization. Dielectric and other relevant electrical properties were measured and the results showed a little possibility in ferroelectric gate random access memory devices.ces.

• Korean Journal of Materials Research
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• v.4 no.2
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• pp.143-151
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• 1994

On PT/Ti/Si substrates, PZT thln fllms are deposited at $300^{\circ}C$ by rf magnetron sputtering uslng a $(PbZr_{52}, Ti_{48})O_{3}$ composltc cerarnlc target. To abtaln, the stable phase, perovskltc structure, furnace annealmg techmque had been cmplo:~d In PbO amb~ent for the $550^{\circ}C$-$750^{\circ}C$ temperature ranges. On Pt(250$\AA$)/Ti(500$\AA$)/Si, Pt(1000)$\AA$/Ti(500$\AA$)/Si substrates, effects of Ti layer and Pt thickness are studled. Though thickness of the Pt layer 1s 1000$\AA$). oxygen diffusion is not prevented and accelerated by Ti layer actlng for oxygen sink sites durmg furnace annealing. The upper TI layer 1s transformed Into TIOX by oxyen dlffuslon and lower Ti layer Into silicide with in-diffused Pt. The formation of TiOx layer seems to affect the orlentatton of the PZT layer. Furnace annealed f~lm shows ferroelectr~c and electrical properties wth a remanent polarlzation of 3.3$\mu A /\textrm{cm}^2$, , coerclve fleld of 0.15MV/cm, a=571 (10kHz), leakage current 32.65$\mu A /\textrm{cm}^2$, , breakdown voltage of 0.4OMV/cm.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.288-288
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• 2013

We report the catalytic activity of Au/$TiO_2$ and Pt/$TiO_2$ nanocatalysts under CO oxidation fabricated by arc plasma deposition (APD), which is a facile dry process with no organic materials involved. Using APD, the catalyst nanoparticles were well dispersed on $TiO_2$ powder with an average particle size (2~4 nm) well below that of nanoparticles prepared by the sol-gel method (10 nm). We found that the average particle size of the dispersed gold nanoparticles can be controlled by changing the plasma discharge voltage of APD. Accordingly, the amount of loaded gold on the $TiO_2$ powder increased with increasing discharge voltage, but the specific surface area of the Au/$TiO_2$ samples decreased. As for catalytic reactivity, Au/$TiO_2$ showed a higher catalytic activity than Pt/$TiO_2$ in CO oxidation. The catalytic activity of the Au/$TiO_2$ samples showed size dependence where higher catalytic activity occurred on smaller gold nanoparticles. The study suggests that APD is a simple way to fabricate catalytically active nanocatalysts.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.68-68
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• 2000

펄스레이저 증착법(이하 PLD)을 이용하여 마이크로파 유전체 소자 및 절연 산화막으로의 응용을 위한 MgTiO3 박막을 다양한 기판상에서 증착하였다. 사파이어 기판에 (a,c-plane Al2O3) 성장된 MgTiO3 박막은 에피텍셜 성장(epitaxial growth)이 되었으며, SiO2/Si 및 Pt/Ti/Si 기판위세 성장된 MgTiO3 박막의 경우 003방향으로 배향(oriented) 되었다. MgTiO3 박막은 450~75$0^{\circ}C$까지 기판온도를 변화시키면서 증착시켰으며, 증착시 산소분압은 50~200 mTorr로 변화시켰다. PLD 증착시 타켓에 조사된 레이저 에너지 밀도는 약 2J/cm2였으며, MgTiO3 박막 증착후 200Torr O2 분위기에서 상온까지 1$0^{\circ}C$/min 의 속도로 냉각시켰다. 사파이어 c-plane 상에서 일머나잇(ilminite) MgTiO3 구조가 55$0^{\circ}C$ 에피텍셜 성장하는 것을 관찰할 수 있었으며, 사파이어 a-plane 상에서는 MgTiO3 구조가 $650^{\circ}C$ 이상부터 110방향으로 배향되며 성장하였다. $600^{\circ}C$ 이상에서 c-축으로 배향된 구조를 갖고 있었다. 증착된 MgTiO3 박막의 조성분석(stoichio metric analysis)을 위해 RBS 분석을 수행하여, 증착에 이용된 타켓과 동일한 조성을 갖는 MgTiO3 박막이 성장된 것을 확인할 수 있었다. 사파이어 기판상에 증착된 MgTiO3 박막은 가시영역에서 투명하였으며, 약 270nm 파장을 갖는 영역에서 급격한 흡수단을 보였다. 이때의 MgTiO3 박막은 AFM 분석을 통해 약 0.87mn rms roughness 값을 갖는 매우 평탄한 표면구조를 갖고 있는 것을 확인하였다. MIM(Pt/MgTiO3/Pt) 구조의 캐패시터를 형성시켜 MgTiO3 박막의 유전특성(dielectric properties)을 관찰하였다. PLD로 성장된 MgTiO3 박막의 유전율(relative dielectric constant)은 약 22였으며, 1MHz에서 약 1.5%의 유전손실(dielectirc loss) 값을 보였다. 또한 이때 MgTiO3 박막은 낮은 유전분산값을 보였다.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.3
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• pp.7-12
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• 1999

In this paper, dielectric and strain properties of (1-f-y)PMN-yPT-xST ceramics investigated with the amount of $\textrm{SrTiO}^3$(ST). The $\textrm{SrTiO}^3$ content is ranged within 1~6㏖%. Another compositions with excess MgO also investigated. As the amount of ST is increased, dielectric constant has a maximum value at 5㏖% composition. The Curie temperature is decreased linearly with increasing the amount of ST. Coercive field and ramnant polarization has a maximum value at l㏖% composition. As for the effects of excess MgO, the dielectric constant has been increased by the addition of excess MgO up to 3㏖% to a 0.8PMN-0.12PT-0.04ST specimen. But the strain has been decreased by the addition of excess MgO.

• Applied Chemistry for Engineering
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• v.28 no.3
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• pp.279-285
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• 2017

In this study, the study of the selective catalytic oxidation (SCO) for controlling the $NH_3$ at $200{\sim}350^{\circ}C$ range was investigated. Physicochemical properties of the catalysts were determined using XRD and XPS analysis. In the case of catalytic activity according to thermal treatment condition, the reduction catalyst showed better activity than that of using the calcination catalyst. It was confirmed that the valence state of reduction catalyst was mainly $Pt^{2+}$ and $Pt^0$ as analyzed by XPS. Also, when comparing the reaction activities of $Pt/TiO_2$ catalysts according to the reduction temperature, the $NH_3$ conversion of the catalyst reduced at $700^{\circ}C$ showed the most excellent activity. However, the best activity of $NH_3$ conversion to $N_2$ was obtained for the catalyst reduced at $600^{\circ}C$.

• Journal of the Korean Chemical Society
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• v.46 no.3
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• pp.242-251
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• 2002

We report the synthesis and characterization of the perovskite nanotubes made by sol-gel template syn-thesis.Both lead titanate (PbTiO3 : PT), lead zirconate (PbZrO3 : PZ) and lead zirconium titanate (PbZrO3 -PbTiO3 : PZT) solid solution nanotubes were prepared with a chelate sol-gel of titanium isopropoxide (Ti(OPri)4 ), zirconium tet-rabutoxide (Zr(OBu)4 ) and the respective lead acetate (Pb(OAc)2 -3H2O). WhatmanRanodisc membranes, with a 200nm pore size, served as the template. After the removal of the template in the 6M-NaOH, scanning electron microscopy shows that the shapes formed are 200 nm outer diameter tubes with 50mm lengths. Transmission electron microscopy and electron diffraction reveal that the tubes are polycrystalline. The PT nanotubes so far have shown an anomalous transition temperature, 234.4$^{\circ}C$ as measured by DSC with a small particle size, 15.4 nm determined by X-ray analysis with the aid of Scherrer's equation.

• Journal of the Korean Ceramic Society
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• v.49 no.3
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• pp.253-259
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• 2012

In this study, crystal structural changes and dielectric properties of $(1-x)Pb(Yb_{1/2}Nb_{1/2})O_3-xPbTiO_3$ ((1-x)PYN-xPT) solid solutions were measured and analyzed with respect to the $PbTiO_3$ (PT) contents ($0.40{\leq}x{\leq}0.60$). From X-ray diffraction (XRD) measurements, (1-x)PYN-xPT solid solutions showed changes of the crystal structure from pseudocubic ($0.40{\leq}x{\leq}0.44$) to tetragonal ($0.52{\leq}x{\leq}0.60$) on increasing PT contents and exhibited the coexistence of pseudocubic and tetragonal phase near the morphotropic phase boundary (MPB) composition ($0.46{\leq}x{\leq}0.50$). The dielectric constant showed a maximum value at x = 0.46 and the maximum values in (1-x)PYN-xPT decreased with higher PT contents. The phase transition temperatures of (1-x)PYN-xPT solid solutions increased over the whole composition ranges tested ($0.40{\leq}x{\leq}0.60$).

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.144.2-144
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• 2000