• Title/Summary/Keyword: $WO_3$ films

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Fabrication and Characterization of Thin Film Supercapacitor using $WO_3$ ($WO_3$를 이용한 박막형 슈퍼캐패시터의 제작 및 특성 평가)

  • 신호철;신영화;임재홍;윤영수
    • 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/$\textrm{cm}^2$-${\mu}{\textrm}{m}$.

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Characteristics of CuO doped WO3-SnO2 Thick Film Gas Sensors (CuO가 첨가된 WO3-SnO2 후막 가스센서 특성 연구)

  • Lee, Don-Kyu;Shin, Deuck-Jin;Yu, Il
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.12
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    • pp.956-960
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    • 2010
  • CuO doped $WO_3-SnO_2$ thick film gas sensors were fabricated by screen printing method on alumina substrates and heat-treated at $350^{\circ}C$ in air. The effects of mixing ratio of $WO_3$ with $SnO_2$ on the structural and morphological properties of $WO_3-SnO_2$ were investigated X-ray diffraction and Scanning Electron Microscope. The structural properties of the $WO_3-SnO_2$:CuO thick film by XRD showed that the monoclinic of $WO_3$ and the tetragonal of $SnO_2$ phase were mixed. Nano CuO was coated on the $WO_3-SnO_2$ surface and then the surface of $WO_3$ was coated with $SnO_2$ particles with $1\sim1.5{\mu}m$ in diameters, as confirmed form the SEM image. The sensitivity of the $WO_3-SnO_2$:CuO sensor to 2000 ppm $CO_2$ gas and 50 ppm $H_2S$ gas for the various ratio of $WO_3$ and $SnO_2$ was investigated. The 4 wt% CuO doped $WO_3-SnO_2$(75:25) tkick films showed the highest sensitivity to $CO_2$ gas and $H_2S$ gas.

The Effects of Pre-Annealing on Electrochemical Preparation for Nanoporous Tungsten Oxide Films (전기화학적 제조를 통한 나노다공성 텅스텐 산화물 성장의 전열처리 영향)

  • Kim, Sun-Mi;Kim, Kyung-Min;Choi, Jin-Sub
    • Journal of the Korean Electrochemical Society
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    • v.14 no.3
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    • pp.125-130
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    • 2011
  • We describe that the surface and thickness of nanoporous $WO_3$ fabricated by both light-induced and light-absent anodization are affected by pre-annealing process from $200^{\circ}C$ to $600^{\circ}C$. As a result, the nanoporous $WO_3$ with a thickness of $1.83{\mu}m$ can be achieved by anodization for 6 hours after pre-annealing at $400^{\circ}C$ without illumination of light. Moreover, the thickness of nanoporous $WO_3$ fabricated by pre-annealing is thicker than that of $WO_3$ prepared by non-annealing process. However, the light illumination during anodization leads to convert the crystalline structure obtained by pre-annealing, which interfere the growth of nanoporous $WO_3$. In this paper, we discuss about the growth mechanism of these different nanoporous $WO_3$ films.

A Study on Micro Gas Sensor Utilizing WO$_3$ Thin Films Fabricated by Sputtering Method (스퍼터링법으로 제작한 WO$_3$ 박막을 이용한 NO$_2$ 마이크로 가스센서에 관한 연구)

  • 김창교;이영환;노일호;유홍진;유광수;기창진
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.4 no.3
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    • pp.139-144
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    • 2003
  • A flat type micro gas sensor was fabricated on the p-type silicon wafer with low stress Si$_3$N$_4$, whose thickness is 2 ${\mu}{\textrm}{m}$, using MEMS technology. WO$_3$ thin film as a sensing material for detection of NO$_2$ gas was deposited using a tungsten target by sputtering method, followed by thermal oxidation at several temperatures (40$0^{\circ}C$-$600^{\circ}C$) for one hour. NO$_2$ sensitivities were investigated for the WO$_3$ thin films with different annealing temperatures. The highest sensitivity was obtained for the samples annealed at $600^{\circ}C$ when it was operated at 20$0^{\circ}C$. The results of XRD analysis showed the annealed samples had polycrystalline phase mixed with triclinic and orthorhombic structures. The sample exhibits higher sensitivity when the system has less triclinic structure. The sensitivities, $R_{gas}/R_{air},$ operating at 20$0^{\circ}C$ to 5 ppm NO$_2$ of the sample annealed at $600^{\circ}C$ were approximately 90.

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NO2 Sensing Characteristics of WO3 Thick Film Sensors Using Nanosized WO3 Powders Prepared by Sol-Precipitation Process (Sol-Precipitation법으로 제조된 WO3 나노분말을 이용한 후막 센서의 NO2 감지 특성)

  • Ryu, Hyun-Wook;Park, Kyung-Hee;Kim, In-Chun;Hong, Kwang-Joon;Park, Jin-Seong
    • Korean Journal of Materials Research
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    • v.12 no.12
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    • pp.930-934
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    • 2002
  • Nanosized $WO_3$ powders were synthesized by the sol-precipitation process using $WCl_{6}$ as the starting material, ethanol as a solvent and $NH_4$OH solution as a precipitant, followed by a washing-drying treatment and calcination. The effects on the powder crystallinity and microstructure of calcination temperature were investigated with XRD and FE-SEM. The $WO_3$ powders calcined at $500^{\circ}C$ and $700^{\circ}C$ showed good crystallinity and their mean particle size was 30nm and 70nm, respectively. These powders were used for the preparation of pastes which were printed as thick films on alumina substrates with comb-type Pt electrodes. The particle size strongly influenced the $NO_2$ gas sensing property of the thick films. A significant reduction in the $NO_2$ sensitivity was observed for the film prepared from larger particle size, having thus a larger grain size. For the film having a smaller grain size, on the other hand, the higher $NO_2$ sensitivity was observed and the sensitivity increased with $NO_2$ concentration.

Influence of vacuum Pressure on Electrochnnc Properties of $WO_3$ Films (진공도가 텅스텐 산화물 방막의 전기적 착색특성에 미치는 영향)

  • Lee, Kil-Dong
    • Solar Energy
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    • v.17 no.4
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    • pp.67-74
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    • 1997
  • The electrochromic $WO_3$ thin films were prepared by using the electron beam deposition technique. The influences of vacuum pressure were examined in terms of the surface morphology and the electrochromic properties of films. From the results, the electrochromic behavior of electron beam deposited films strongly depends on the vacuum pressure during deposition. The film prepared under a vacuum pressure of $5{\times}10^4$ mbar was found to be rather stable when subjected to the repeated coloring and bleaching cycles in an aqueous acid electrolyte of 1M $H_2SO_4$. It was also found that the degraded film by repeated cycling in the aqueous acid solution changed the grain shape of film surface.

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Effect of Reduced Graphene Oxide in Photoanode on Photoelectrochemical Performance in Water Splitting for Hydrogen Production (수소생산을 위한 물 분해용 광전극에 도입된 환원된 산화그래핀이 광전기화학성능에 미치는 영향)

  • YOON, SANGHYEOK;DING, JIN-RUI;KIM, KYO-SEON
    • Transactions of the Korean hydrogen and new energy society
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    • v.27 no.4
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    • pp.329-334
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    • 2016
  • Hydrogen is eco-friendly alternative energy source and the photoelectrochemical water splitting is believed to be one of the promising methods for hydrogen production. Many researchers have studied several potential photocatalysts to increase the photoelectochemical performance efficiency for hydrogen conversion. In this study, the GO (graphene oxide) was prepared by Tour's method and was dispersed in precursor solutions of $WO_3$ and $BiVO_4$. Those precursor solutions were spin-coated on FTO glass and several photocatalyst thin films of $WO_3$, $BiVO_4$ and $WO_3/BiVO_4$ were prepared by calcination. The morphologies of prepared photocatalyst thin films were measured by scanning electron microscope. The photoelectrochemical performances of photocatalyst thin films with rGO (reduced graphene oxide) and without rGO were analyzed systematically.

Study of electrochromic cells in $WO_{3}$/$MoO_{3}$ double-layer structure ($WO_{3}$$ MoO_{3}$ 이중층을 가진 전기변색 소자에 관한 연구)

  • 임석범;임동규;백희원;김영호;조봉희;유인종;변문기
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.07a
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    • pp.515-518
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    • 2000
  • The electrochromic properties of $WO_{3}$/$MoO_{3}$ and $MoO_{3}$/$WO_{3}$ double-layers have been systemically studied. The double-layers were made by a e-beam evaporation method and investigated by studying optical modulation, transmittance, and cyclic voltammetry. The devices exhibit good optical properties with wavelength range of 400 to 1100 nm(visible and infrared) during coloration as a function of lithium ion charge injection. It has shown that the double-layer electrochromic thin films are improved the electrochromic properties, but the electrochemical properties are less stable.

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Electrical Property Changes of $\textrm{NO}_X$ Sensitive $\textrm{WO}_3$ Thin Films as Applied DC Voltages on 8YSZ Substrate (8YSZ 기판에 증착한 $\textrm{WO}_3$ 박막의 DC 전압에 따른 $\textrm{NO}_X$ 감지특성)

  • 전춘배;박기철
    • Journal of the Korean Institute of Telematics and Electronics T
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    • v.36T no.1
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    • pp.8-12
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    • 1999
  • $\textrm{WO}_3$ semiconductive film, which is known to have a sensitivity on $\textrm{NO}_X$ gas was prepared on 8YSZ (8% Yttria stabilized $\textrm{ZrO}_2$) ionic conductor substrate that has oxygen ion pumping effect. Microstructure and electrical properity, especially $\textrm{NO}_X$ sensitivity as a function of DC voltage applied to 8YSZ substrate was examined. When the $\textrm{WO}_3$ film was annealed, it showed amorphous structure, while crystallization was occurred at $600^{\circ}$C revealing orthorhombic phase of $\textrm{WO}_3$. As the annealing temperature increases, (111) and (001) peaks of $\textrm{WO}_3$ film was enhanced. At $400^{\circ}C$ when DC voltage was applied, comparing with no DC bias, more stable and large response characteristics was showed, and the best sensitivity was observed at 2V. Recovery characteristics of NO gas was much better that that of $\textrm{NO}_2$ gas.

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