• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.9
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• pp.397-402
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• 2005

The ($Sr_{1-x}Ca_x)TiO_3(SCT)$ thin films are deposited on Pt-coated electrode (Pt/TiN/SiO$_{2}$Si) using RF sputtering method with substitutional contents of Ca. The optimum conditions of RF power and Ar/O$_{2}$ ratio were 140(W) and 80/20, respectively. Deposition rate of SCT thin film was about $18.75{\AA}$/min. The dielectric constant was increased with increasing the substitutional contents of Ca, while it was decreased if the substitutional contents of Ca exceeded over $15[mol\%]$. The capacitance characteristics had a stable value within $\pm4[\%]$ in temperature ranges of $-80\~+90[^{\circ}C]$. All SCT thin films used in this study show the phenomena of dielectric relaxation with the increase of frequency, and the relaxation frequency is observed above 200[kHz].

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1496-1498
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• 2003

The $(Sr_{0.85}Ca_{0.15})TiO_3$(SCT) thin films were deposited on Pt-coated electrode (Pt/TiN/$SiO_2$/Si) using RF sputtering method according to the deposition condition. The optimum conditions of RF power and Ar/$O_2$ ratio were 140[W] and 80/20, respectively. Deposition rate of SCT thin films was about 18.75[${\AA}/min$] at the optimum condition. The capacitance characteristics had a stable value within ${\pm}4[%]$. The drastic decrease of dielectric constant and increase of dielectric loss in SCT thin films were observed above 200[kHz].

• Journal of the Korean Ceramic Society
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• v.33 no.2
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• pp.177-182
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• 1996

strontium titanate (SrTiO3) thin films deposited on Pt/MgO were prepared by Plasma Enhanced Metal Orgainc Chemical vapor Deposition (Pe-MOCVD). The crystallinity of SrTiO3 thin films increased with increasing depo-sition temperature and SrF2 second phase disappeared at 55$0^{\circ}C$ The films showed a dielectric constant of 177 and a dissipation factor of 0.0195 at 100 kHz. The variation of capacitance of the films with applied voltage was small showing paraelectric properties. The charge storage density and leakage current density were 40fC/${\mu}{\textrm}{m}$2 and 3.49$\times$10-7 A/cm2 at 0.25 MV/cm, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.466.1-466.1
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• 2014

$TiO_2$는 저렴한 가격, 적절한 bandgap, 열적, 화학적, 생물학적 안정성 등으로 촉망받는 광촉매 물질이다. $TiO_2$는 rutile (tetragonal, space group: P42/mnm), anatse (tetragonal, space group: I41/amd), and brookite (orthorhombic, space group: Pbca )의 3가지 대표적인 결정구조를 가지고 있다. Rutile과 anatase는 1972년 Fujishima와 Honda가 $TiO_2$의 광촉매 특성을 발견 한 후로 아주 많은 연구가 되어왔다. 반면 brookite의 경우는 자연에 거의 존재하지 않으며, 합성방법도 어려워서 rutile과 anatase에 비해 많은 연구가 되지 않았다. 본 연구에서는 brookite를 포함한 다양한 $TiO_2$ 나노구조를 간단한 수열합성법으로 티타늄 호일 위에 합성하였다. 합성된 $TiO_2$는 반응 온도와 시간, additive의 농도에 따라서 sheet, tube, wire, pyramidal 의 4가지 morphologies를 가졌다. 이 다양한 morphologies은 SEM과 TEM으로 분석되었으며, 각 물질의 결정 구조는 XRD분석과 TEM의 SAED pattern 분석으로 sheet, tube, wire은 anatase, pyramidal 구조는 brookite라는 것이 확인 되었다. 위의 방법으로 합성된 각각의 $TiO_2$ 물질들을 working 전극으로, Pt와 Ag/AgCl을 reference와 counter 전극으로 만들어서 photoelectrochemical 특성을 측정해서 비교를 해보았을 때, brookite 물질이 anatase보다 더 좋은 photoelectrochemical 특성을 나타내는 것을 확인하였다.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.8
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• pp.823-830
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• 2008

The feasibility study for the application of the photoelectrocatalytic decolorization of Rhodamine B(RhB) was performed in the slurry photoelectrochemical reactor with powder TiO$_2$. The photoelectrocatalytic process was consisted of powder TiO$_2$, Pt electrode and three 8 W UV-C lamps. The effects of operating conditions, such as current, electrolyte, air flow rate and electrode material were evaluated. The experimental results showed that optimum TiO$_2$ dosage and current in photoelectrocatalytic process were 0.4 g/L and 0.02 A, respectively. It was found that the RhB could be degraded more efficiently by this photoelectrocatalytic process than the sum of the two individual oxidation processes(photocatalytic and electrolytic process). It demonstrated a synergetic effect between the photo- and electrochemical catalysis. Photoelectrocatalytic process was affected to air flow rate and optimum air flow rate was 2 L/min. The electrode material and NaCl effect of decolorization of RhB were not significant within the experiment conditions.

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.816-819
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• 1995

(Ba$_{1-x}$ , Sr$_{x}$)TiO/$_3$thin films on Pt/Ti/SiO$_2$/Si substrates were prepared by LP MOCVD(Low Pressure Metal-Organic Chemical Vapor Deposition). The crystalinity of BST deposit had a (100) preferred orientation with increasing deposition temperature due to surface diffusion. BST films deposited at 90$0^{\circ}C$ showed a dielectric constant of 365 and a dissipation factor of 0.052 at a frequency of 100kHz. The chance of capacitance of the films with applied voltage was small, showing paraelectric properties. BST film deposited at 90$0^{\circ}C$ had a charge storage density of 60 fc/${\mu}{\textrm}{m}$$^2$at a field of 0.2MV/cm and the leakage current density of 20 nA/$\textrm{cm}^2$ at a field of 0.15 MV/cm.cm.

• Korean Journal of Materials Research
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• v.7 no.1
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• pp.33-39
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• 1997

Single phase pero~~skite lead lanthanum titanate thin films were fabricated on $Pt/Ti/SiO_2/Si$ substrates at the temperature of $480^{\circ}C$ by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD) using metal organic sources $Pb(DPM)_2$ pre-flowing treatment in ECIi oxygen plasma before fabricating PLT films 11romote the perovskite nucleation due to stable supplying of the $Pb(DPM)_2$ and providing the F'h-rich atmosphere in the early stage of deposition. $Pb(DPM)_2$ pie-flonring treatment enhanced the properties of PLT films. The charactcristics of the PLT filrris were investigated as a tunction of the flow rate of Ti-source. The PL'i' films were grown in a perovskite structure tvith (100) preferred orientation. The high X-ray diffraction intensity and dielectric constant were obtained from the stoichiometric perovskite $(Pb,La)TiO_3$.

• Journal of the Korean Ceramic Society
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• v.44 no.8
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• pp.403-406
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• 2007

Ferroelectric Ce-doped $Bi_4Ti_3O_{12}$ (BCT) thin films were deposited by liquid delivery metal organic chemical vapor deposition (MOCVD) onto a $Pt(111)/Ti/SiO_2/Si(100)$ substrate. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to identify the crystal structure, the surface, and the cross-section morphology of the deposited ferroelectric flims. After annealing above $640^{\circ}C$, the BCT films exhibited a polycrystalline structure with preferred (001) and (117) orientations. The BCT lam capacitor with a top Pt electrode showed a large remnant polarization ($2P_r$) of $44.56{\mu}C/cm^2$ at an applied voltage of 5 V and exhibited fatigue-free behavior up to $1.0{\times}10^{11}$ switching cycles at a frequency of 1 MHz. This study clearly reveals that BCT thin film has potential for application in non-volatile ferroelectric random access memories and dynamic random access memories.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.575-578
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• 2000

In this work, all solid-state thin film supercapacitor(TFSC) was fabricated using tungsten trioxide (WO$_3$) with a structure WO$_3$/LiPON/WO$_3$/Pt/TiO$_2$/Si (substrate). After TiO$_2$ was deposited on Si(100) wafer by d.c. reactive sputtering, the Pt current collector films were grown on TiO$_2$glue layer without breaking vacuum by d.c. sputtering. Fabrication conditions of WO$_3$ thin film were such that substrate temperature, working pressure, gas ratio of $O_2$/Ar and r.f. power were room temperature, 5 mTorr, 20% (O$_2$(8sccm)/Ar(32sccm)) and 200W, respectively. LiPON electrolyte film were grown on the WO$_3$ film using r.f. magnetron sputtering at room temperature. The XRD pattern of the as-deposited WO$_3$ thin film were shown no crystalline peak (amorphous). The SEM image of as-deposited WO$_3$ thin film showed that the surface is smooth and uniform. The capacitiy of as-fabricated TFSC was 0$\times$10$^{-2}$ F/$\textrm{cm}^2$-${\mu}{\textrm}{m}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.209-209
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• 2010

Multiferroic properties of $BaTiO_3-CuFe_2O_4$ thin films grown on highly-textured Pt(111)/$TiO_2/SiO_2$/Si(100) substrates were studied. $CuFe_2O_4$ ceramic target was synthesized by mixing oxide powders of CuO, $Fe_2O_03$, $BaTiO_3$ ceramic target was also prepared separately. The film structure was of bi-layer type, where $BaTiO_3$ layer lies underneath of $CuFe_2O_4$ layer, where both layers were grown by pulsed laser deposition technique. We will report the ferroelectric and magnetic properties of $BaTiO_3-CuFe_2O_4$ bi-layer films in some detail.