• Title/Summary/Keyword: Thin film sensor

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Fabrication of low-stress silicon nitride film for application to biochemical sensor array

  • Sohn, Young-Soo
    • Journal of Sensor Science and Technology
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    • v.14 no.5
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    • pp.357-361
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    • 2005
  • Low-stress silicon nitride (LSN) thin films with embedded metal line have been developed as free standing structures to keep microspheres in proper locations and localized heat source for application to a chip-based sensor array for the simultaneous and near-real-time detection of multiple analytes in solution. The LSN film has been utilized as a structural material as well as a hard mask layer for wet anisotropic etching of silicon. The LSN was deposited by LPCVD (Low Pressure Chemical Vapor Deposition) process by varing the ratio of source gas flows. The residual stress of the LSN film was measured by laser curvature method. The residual stress of the LSN film is 6 times lower than that of the stoichiometric silicon nitride film. The test results showed that not only the LSN film but also the stack of LSN layers with embedded metal line could stand without notable deflection.

Investigation of piezoelectric ceramic size effect for miniaturing the piezoelectric energy harvester (소형 압전 에너지 하베스터 구현을 위한 세라믹 크기 변화)

  • Kim, Hyung-Chan;Jung, Woo-Suk;Kang, Chong-Yun;Yoon, Seok-Jin;Ju, Byeong-Kwon;Jeong, Dae-Yong
    • Journal of Sensor Science and Technology
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    • v.17 no.4
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    • pp.267-272
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    • 2008
  • Energy harvesting from the vibration through the piezoelectric effect has been studied for powering the small wireless sensor nodes. As piezoelectric uni-morph cantilever structure can transfer low vibration to large displacement, this structure was commonly deployed to harvest electric energy from vibrations. Through our previous results, when stress was applied on the cantilever, stress was concentrated on the certain point of the ceramic of the cantilever. In this study, for miniaturing the energy harvester, we investigated how the size of ceramics and the stress distribution in ceramic affects energy harvester characteristics. Even though the area of ceramic was 28.6 % decreased from $10{\times}35{\times}0.5mm^3$ to $10{\times}25{\times}0.5mm^3$, both samples showed almost same maximum power of 0.45 mW and the electro-mechanical coupling factor ($K_{31}$) of 14 % as well. This result indicated that should be preferentially considered to generate high power with small size energy harvester.

Thermoelectric properties of La(1-x)MxCoO3(M=Sr, Ca;x=0, 0.1) ceramics for thermal sensors

  • Kang, Min-Gyu;Cho, Kwang-Hwan;Kang, Chong-Yun;Kim, Jin-Sang;Kim, Sang-Sig;Yoon, Seok-Jin
    • Journal of Sensor Science and Technology
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    • v.18 no.3
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    • pp.234-238
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    • 2009
  • We have investigated the effects of dopant on the thermoelectric properties that $La_{(1-x)}M_xCoO_3$(M=Sr, Ca;x=0, 0.1) bulk ceramics fabricated by the conventional solid state reaction method. The Seebeck coefficient of $La_{(1-x)}M_xCoO_3$(M=Sr, Ca;x=0, 0.1) bulk ceramics was measured at wide temperature range from 300 K to 673 K. The thermoelectric properties(Seebeck coefficient and electrical resistivity) depend strongly on the kinds of dopants. Sr and Ca dopant decrease the Seebeck coefficient. Density of sintered $La_{0.9}Sr_{0.1}CoO_3$ ceramic at 1523 K was 7.12 $g/cm^2$ and Seebeck coefficient was 35 ${\mu}V/K$ at 663 K. However, the electrical resistivity of the Sr doped sample was low and stable.

Fabrication of oxide semiconductor thin film gas sensor array (산화물 반도체 박막 가스센서 어레이의 제조)

  • 이규정;김석환;허창우
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.4 no.3
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    • pp.705-711
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    • 2000
  • A thin film oxide semiconductor micro gas sensor array which shows only 60 mW of power consumption at an operating temperature of $300^{\circ}C$ has been fabricated using microfabrication and micromachining techniques. Excellent thermal insulation of the membrane is achieved by the use of a double-layer structure of $0.1\mum\; thick\; Si_3N_4 \;and\; 1 \mum$ thick phosphosilicate glass (PSG) prepared by low-pressure chemical-vapor deposition (LPCVD) and atmospheric-pressure chemical-vapor deposition (APCVD), respectively. The sensor array consists of such thin film oxide semiconductor sensing materials as 1 wt.% Pd-doped $SnO_2,\; 6 wt.% A1_2O_3-doped\; ZnO,\; WO_3$/ and ZnO. Baseline resistances of the four sensing materials were found to be stable after the aging for three days at $300^{\circ}C$. The thin film oxide semiconductor micro gas sensor array exhibited resistance changes usable for subsequent data processing upon exposure to various gases and the sensitivity strongly depended on the sensing layer materials.

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Zinc Oxide Wire-Like Thin Films as Nitrogen Monoxide Gas Sensor

  • Hung, Nguyen Le;Kim, Hyojin;Kim, Dojin
    • Korean Journal of Materials Research
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    • v.25 no.7
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    • pp.358-363
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    • 2015
  • We present an excellent detection for nitrogen monoxide (NO) gas using polycrystalline ZnO wire-like films synthesized via a simple method combined with sputtering of Zn metallic films and subsequent thermal oxidation of the sputtered Zn nanowire films in dry air. Structural and morphological characterization revealed that it would be possible to synthesize polycrystalline hexagonal wurtzite ZnO films of a wire-like nanostructure with widths of 100-150 nm and lengths of several microns by controlling the sputtering conditions. It was found from the gas sensing measurements that the ZnO wire-like thin film gas sensor showed a significantly high response, with a maximum value of 29.2 for 2 ppm NO at $200^{\circ}C$, as well as a reversible fast response to NO with a very low detection limit of 50 ppb. In addition, the ZnO wire-like thin film gas sensor also displayed an NO-selective sensing response for NO, $O_2$, $H_2$, $NH_3$, and CO gases. Our results illustrate that polycrystalline ZnO wire-like thin films are potential sensing materials for the fabrication of NO-sensitive high-performance gas sensors.

Fabrication and characteristics of ITO thin films on CR39 substrate for transparent OTFT

  • Kwon, Sung-Yeol
    • Journal of Sensor Science and Technology
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    • v.16 no.3
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    • pp.229-233
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    • 2007
  • The indium tin oxide (ITO) films were deposited on CR39 substrate using DC magnetron sputtering. The ITO thin films deposited at room temperature because CR39 substrate its glass-transition temperature is $130^{\circ}C$. The ITO thin films used bottom and top electrode and for organic thin film transparent transistors (OTFTs). The ITO thin film electrodes electrical properties and optical transparency properties in the visible wavelength range (300-800 nm) strongly dependent on volume of oxygen percent. For the optimum resistivity and transparency of the ITO thin film electrode achieved with a 75 W plasma power, 10 % volume of oxygen and a 27 nm/min deposition rate. Above 85 % transparency in the visible wavelength range (300-800 nm) measured without post annealing process and a low resistivity value $9.83{\times}10^{-4}{\Omega}cm$ was measured thickness of 300 nm. All fabrication process of ITO thin films did not exceed $80^{\circ}C$.

Transfer of Heat-treated ZnO Thin-film Plastic Substrates for Transparent and Flexible Thin-film Transistors (투명 유연 박막 트랜지스터의 구현을 위한 열처리된 산화아연 박막의 전사방법 개발)

  • Kwon, Soon Yeol;Jung, Dong Geon;Choi, Young Chan;Lee, Jae Yong;Kong, Seong Ho
    • Journal of Sensor Science and Technology
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    • v.27 no.3
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    • pp.182-185
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    • 2018
  • Zinc oxide (ZnO) thin films have the advantages of growing at a low temperature and obtaining high charge mobility (carrier mobility) [1]. Furthermore, the zinc oxide thin film can be used to control application resistance depending on its oxygen content. ZnO has the desired physical properties, a transparent nature, with a flexible display that makes it ideal for use as a thin-film transistor. Though these transparent flexible thin-film transistors can be manufactured in various manners, manufacturing large-area transistors using a solution process is easier owing to the low cost and flexible substrate. The advantage of being able to process at low temperatures has been attracting attention as a preferred method. However, in the case of a thin-film transistor fabricated through a solution process, it is reported that charge mobility is lower. To improve upon this, a method of improving the crystallinity through heat treatment and increasing electron mobility has been reported. However, as the heat treatment temperature is relatively high at $500^{\circ}C$, an application where a flexible substrate is absent would be more suitable.

The Construction of the SPR (Surface Plasmon Resonance) Sucrose Sensor (표면 플라즈몬 공명형 자당 센서의 제작)

  • Um, N.S.;Lee, S.M.;Hahm, S.H.;Koh, K.N.;Lee, S.H.;Kang, S.W.
    • Journal of Sensor Science and Technology
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    • v.7 no.4
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    • pp.279-284
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    • 1998
  • A surface plasmon resonance (SPR) sensor system for the determination of sucrose concentration was constructed with a gold thin film sensing chip. The properties of gold thin film are critical factors in exciting surface plasmon resonance phenomena. Therefore in the present paper, the fabrication conditions of gold thin film were investigated to optimize the SPR phenomena. The optimum thickness was obtained as $545{\AA}$ with $43.75^{\circ}$ resonance angle and good surface roughness limitation. about $3{\AA}$. The linear resonance angle shifts and rapid response were observed from the sucrose concentrations ranged from 0 to 40wt%.

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New Fabrication method of Planar Micro Gas Sesnor Array (집적도를 높인 평면형 가스감지소자 어레이 제작기술)

  • 정완영
    • Proceedings of the IEEK Conference
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    • 2003.07b
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    • pp.727-730
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    • 2003
  • Thin tin oxide film with nano-size particle was prepared on silicon substrate by hydrothermal synthetic method and successive sol-gel spin coating method. The fabrication method of tin oxide film with ultrafine nano-size crystalline structure was tried to be applied to fabrication of micro gas sensor array on silicon substrate. The tin oxide film on silicon substrate was well patterned by chemical etching upto 5${\mu}{\textrm}{m}$width and showed very uniform flatness. The tin oxide film preparation method and patterning method were successfully applied to newly proposed 2-dimensional micro sensor fabrication.

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Mechanical characteristics of polycrystalline 3C-SiC thin films using Ar carrier gas by APCVD (순 아르콘 캐리어 가스와 APCVD로 성장된 다결정 3C-SiC 박막의 기계적 특성)

  • Han, Ki-Bong;Chung, Gwiy-Sang
    • Journal of Sensor Science and Technology
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    • v.16 no.4
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    • pp.319-323
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    • 2007
  • This paper describes the mechanical characteristics of poly 3C-SiC thin films grown on Si wafers with thermal oxide. In this work, the poly 3C-SiC thin film was deposited by APCVD method using only Ar carrier gas and single precursor HMDS at $1100^{\circ}C$. The elastic modulus and hardness of poly 3C-SiC thin films were measured using nanoindentation. Also, the roughness of surface was investigated by AFM. The resulting values of elastic modulus E, hardness H and the roughness of the poly 3C-SiC film are 305 GPa, 26 GPa and 49.35 nm respectively. The mechanical properties of the grown poly 3C-SiC film are better than bulk Si wafers. Therefore, the poly 3C-SiC thin film is suitable for abrasion, high frequency and MEMS applications.