• Title/Summary/Keyword: 광전류

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Feasibility of Optoelectronic Neural Stimulation Shown in Sciatic Nerve of Rats (흰쥐의 좌골 신경 자극을 통한 광전 자극의 가능성에 대한 연구)

  • Kim Eui tae;Oh Seung jae;Baac Hyoung won;Kim Sung june
    • Journal of Biomedical Engineering Research
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    • v.25 no.6
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    • pp.611-615
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    • 2004
  • A neural prostheses can be designed to permit stimulation of specific sites in the nervous system to restore their functions, lost due to disease or trauma. This study focuses on the feasibility of optoelecronic stimulation into nervous system. Optoelectronic stimulation supplies, power and signal into the implanted optical detector inside the body by optics. It can be effective strategy especially on the retinal prosthesis, because it enables the non-invasive connection between the external source and internal detector through natural optical window 'eye'. Therefore, we designed an effective neural stimulating setup by optically based stimulation. Stimulating on the sciatic nerve of a rat with proper depth probe through optical stimulation needs higher ratio of current spreading through the neural surface, because of high impedance of neural interface. To increase the insertion current spreading into the neuron, we used a parallel low resistance compared to load resistance organic interface and calculated the optimized outer parallel resistance for maximum insertion current with the assumption of limited current by photodiode. Optimized outer parallel resistance was at a range of 500Ω-700Ω and a current was at a level between 580uA and 650uA. Stimulating current efficiency from initial photodiode induced current was between 47.5 and 59.7%. Various amplitude and frequency of the optical stimulation on the sciatic nerve showed the reliable visual tremble, and the action potential was also recorded near the stimulating area. These result demonstrate that optoelectronic stimulation with no bias can be applied to the retinal prosthesis and other neuroprosthetic area.

Growth and photocurrent properties for the $AgInS_{2}$ epilayers by hot wall ep itaxy (Hot wall epitaxy 방법에 의한 $AgInS_{2}$ 박막의 성장과 광전류특성)

  • Hong, K.J.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.08a
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    • pp.92-96
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    • 2002
  • A silver indium sulfide $(AgInS_{2})$ epilayer was grown by the hot wall epitaxy method, which has not been reported in the literature. The grown $AgInS_{2}$ epilayer has found to be a chalcopyrite structure and evaluated to be high quality crystal. From the photocurrent measurement in the temperature range from 30 K to 300 K, the two peaks of A and B were only observed, whereas the three peaks of A, B, and C were seen in the PC spectrum of 10 K. These peaks are ascribed to the band-ta-band transition. The valence band splitting of $AgInS_{2}$ was investigated by means of the photocurrent measurement. The crystal field splitting, $\Delta_{cr}$, and the spin orbit splitting, $\Delta_{so.}$ have been obtained to be 0.150 eV and 0.009 eV at 10 K, respectively. And, the energy band gap at room temperature has been determined to be 1.868 eV. Also, the temperature dependence of the energy band gap, $E_{g}(T)$, was determined.

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The Image Sensor Operating by Thin Film Transistor (박막트랜지스터에 의해 구동되는 이미지센서)

  • Hur Chang-wu
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.1
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    • pp.111-116
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    • 2006
  • In this paper, the image sensor using the a-Si:H TFT is proposed. The optimum amorphous silicon thin film is deposited using plasma enhanced chemical vapor deposition (PECVD). TFT and photodiode both with the thin film are fabricated and form image sensor. The photodiode shows that Idark is $10^{-12}A$, Iphoto is $10^{-9}A$ and Iphoto/Idark is $10^3$, respectively. In the case of a-Si:H TFT, it indicates that Ion/Ioff is $10^6$, the drain current is a few ${\mu}A$ and Vth is $2\~4$ volts. For the analysis on the fabricated image sensor, the reverse bias of -5 voltage in ITO of photodiode and $70{\mu}sec$ pulse in the gate of TFT are applied. The image sensor with good property was conformed through the measured photo/dark current.

The Properties of Electrical Conduction and Photoconduction in Polyphenylene Sulfide(PPS) by Uniaxial Elongation (일축연신에 따른 Polyphenylene sulfide(PPS)의 전기전도 및 광전도 특성)

  • 이운용;장동욱;강성화;임기조;류부형
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1998.06a
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    • pp.223-226
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    • 1998
  • In this paper, we have investigated how morphology and electrical properties in Polyphenylene sulfide(PPS) are changed by uniaxial elongation. XRD pattern shows that interplanar distance and crystallinities are decreased by increasing elongation ratio. Electrical conduction mechanism of PPS is explained as schottky emission from analysis of electrical current. The electrical current is decreased by increasing elongation ratio. The conductivity is changed remarkably above the glass transition temperature around $(82^{\circ}C)$. The band gap of PPS is evaluated as 3.9-4(eV) from the results of photoconductivity. Increarnent of elongation ratio gives us some information about deep trap formation from photocurrent.

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The Properties of Electrical Conduction and Photoconduction in polyphenylene Sulfide(PPS) by Uniaxal Elongation (일축연신에 따른 Polyphenylene Sulfide(PPS)의 전기전도 및 광전도 특성)

  • Lee, Un-Yong;Jang, Dong-Uk;Shin, Tae-Su;Lim, kee-Joe;Ryu, Boo-Hyun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.11 no.10
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    • pp.763-767
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    • 1998
  • In this paper, it is investigated how the morphology and electrical properties in Polyphenylene Sulfide(PPS) changed by uniaxial elongation. XRD(X-ray diffraction) pattern shows that interplanar distance and crystallinities are decreased by increasing elongation ratio. electrical conduction mechanism of PPS is explained as Schottky emission mechanism. the electrical current is decreased by increasing elongation ratio. The conductivity is changed considerably above the glass transition temperature around 82(>$^{\circ}C$). The band gap of PPS is evaluated as 3.7~4(eV)

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The optical CT output signal characteristic according to a light source (광원에 따른 광CT의 출력특성 연구(2))

  • 전재일;정철우;안미경;박원주;이광식;김정배;김민수
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2003.11a
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    • pp.223-226
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    • 2003
  • 본 연구에서는 패러데이 효과(Faraday Effect)를 이용한 초고압 전력설비에서의 광전류 센서의 특성에 대한 기초 연구를 하였다. 광원은 Laser Diode(1310[nm])를 사용하고, 수신부는 PIN-Photodiode를 사용하였다. 센싱부로 사용한 광섬유는 single mode unjacked fiber를 사용하였고, 편광기를 사용하여 빛의 광학적인 편파면을 이용한 전류측정이 가능함을 확인할 수 있었다. 측정 결과에서는 전류에 따른 출력 신호가 나옴으로써 기존 문헌상의 결과와 동일하다는 것을 알 수 있었고 센싱부로 사용한 파이버의 길이에 따른 출력차이를 통해 파이버의 길이가 길수록 강도가 커진다는 것을 알 수 있었다. 또한 길이에 따라 출력의 차이뿐만 아니라 선형성까지도 차이가 난다는 것을 알 수 있었다. reference 값과 광전류센서의 출력 강도와의 오차율을 구했을 때 5[m] 10[m]길이의 광섬유 각각에 대해서 1000[A]이상의 값에서 각각 약 -0.9[%], -0.4[%]의 오차율을 보임을 확인했다. 여기서 인가한 전류값과 길이 즉, 감은 수에 따라 그 오차율이 점점 나아질 수 있다는 것을 알 수 있었다.

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