• Title/Summary/Keyword: Space-Charge-Limited Current

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Discharge Characteristics of a KSTAR NBI Ion Source

  • Chang Doo-Hee;Oh Byung-Hoon
    • Nuclear Engineering and Technology
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    • v.35 no.3
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    • pp.226-233
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    • 2003
  • The discharge characteristics of a prototype ion source was investigated, which was developed and upgraded for the NBI (Neutral Beam Injection) heating system of KSTAR (Korea Superconducting Tokamak Advanced Research). The ion source was designed for the arc discharge of magnetic bucket chamber with multi-pole cusp fields. The ion source was discharged by the emission-limited mode with the control of filament heating voltage. The maximum ion density was 4 times larger than the previous discharge controlled by a space-charge-limited mode with fully heated filament. The plasma (ion) density and arc current were proportional to the filament voltage, but the discharge efficiency was inversely proportional to the operating pressure of hydrogen gas. The maximum ion density and arc current were obtained with constant arc voltage ($80{\sim}100V$), as $8{\times}10^{11}cm^{-3}$ and 1200 A, respectively. The estimated maximum beam current was about 35 A, extracted by the accelerating voltage of 80kV.

Electrical characteristics of the this film interface of amorphous chalcogenide semiconductor (비정질 칼코게나이드 반도체 박막 경계면의 전기적 특성)

  • 박창엽
    • 전기의세계
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    • v.29 no.2
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    • pp.111-117
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    • 1980
  • Contacts formed by vacuum evaporation of As-Te-Si-Ge chalcogenide glass onto Al metal (99.9999%) are studied by measuring paralle capacitance C(V), Cp(w), resistance R(V), Rp(w), and I-V characteristics. The fact that contact metal alloying produced high-resistance region is confirmed from the measurements of parallel capacitance and resistance. From the I-V characteristics in the pre-switcing region, it is found that electronic conduction and sitching occurs in the vicinity of metal-amorphous semiconductor interface. From the experimental obsevations, it is concuded that the current flow in the thin film is space-charge limited current (SCLC) due to the tunneling of electrons through the energy barriers.

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Electrical Conduction Mechanism in ITO/Alq3/Al Organic Light-emitting Diodes

  • Chung, Dong-Hoe;Lee, Joon-Ung
    • Transactions on Electrical and Electronic Materials
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    • v.5 no.1
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    • pp.24-28
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    • 2004
  • We have used ITO/Alq$_3$/Al structure to study electrical conduction mechanism in organic light-emitting diodes. Current-voltage-luminance characteristics were measured at room temperature by varying the thickness of Alq$_3$ layer from 60 to 400mm. We were able to confirm that there are three different mechanisms depending on the applied voltage region; ohmic, space-charge-limited current, and trap-charge-limit-current mechanism. And the maximum luminous efficiency was obtained when the thickness of Alq$_3$ layer is 200nm.

A Study of the Electrical Characteristics of WOx Material for Non-Volatile Resistive Random Access Memory (비-휘발성 저항 변화 메모리 응용을 위한 WOx 물질의 전기적 특성 연구)

  • Jung, Kyun Ho;Kim, Kyong Min;Song, Seung Gon;Park, Yun Sun;Park, Kyoung Wan;Sok, Jung Hyun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.29 no.5
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    • pp.268-273
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    • 2016
  • In this study, we observed current-voltage characteristics of the MIM (metal-insulator-metal) structure. The $WO_x$ material was used between metal electrodes as the oxide insulator. The structure of the $Al/WO_x/TiN$ shows bipolar resistive switching and the operating direction of the resistive switching is clockwise, which means set at negative voltage and reset at positive voltage. The set process from HRS (high resistance state) to LRS (low resistance state) occurred at -2.6V. The reset process from LRS to HRS occurred at 2.78V. The on/off current ratio was about 10 and resistive switching was performed for 5 cycles in the endurance characteristics. With consecutive switching cycles, the stable $V_{set}$ and $V_{reset}$ were observed. The electrical transport mechanism of the device was based on the migration of oxygen ions and the current-voltage curve is following (Ohm's Law ${\rightarrow}$ Trap-Controlled Space Charge Limited Current ${\rightarrow}$ Ohm's Law) process in the positive voltage region.

A Study on the Transference Mechanism of Charge carriers within the Devices (소자 내부에서 전하 운송체의 이동 메카니즘에 관한 연구)

  • Shim, Hye-Yeon;Kim, Jun-Ho;Kim, Young-Kwan
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.07a
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    • pp.508-509
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    • 2005
  • In case of ITO/MEH-PPV/Al structure, the quantity of charge carriers flowing through the organic material was few and the density of them is fixed. The electric field inside of the device almost didn't change with the position. On the other hands, in case of Au/MEH-PPV/Au structure, the hole density increased rapidly nearby the anode but decreased nearby the cathode. The space charge phenomenon followed sufficient hole injection resulted in the change of the electric field with the position inside of the device. We verified that the result of the current-voltage simulation corresponded with experimental result.

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Characteistics of Charge Traps and Poling Behavior of Poly (Vinylidene Fluoride)

  • Seo Jeong Won;Ryoo Kun Sang;Lee Hoo Sung
    • Bulletin of the Korean Chemical Society
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    • v.6 no.4
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    • pp.218-221
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    • 1985
  • Transient charging and discharging currents as well as space charge limited currents have been measured in biaxially stretched poly(vinylidene fluoride) film under various poling fields and temperatures. At low temperatures and short poling times, the I-V characteristics showed shallow trap behavior. When the current values extrapolated to the infinite time, the I-V characteristics indicate that the distribution of the trap energy levels is uniform or very broad. The abnormal suppression of current at higher poling voltages and the high discharge rate observed also in the same voltage range are attributed to the morphological changes due to dipole reorientation.

Energy Band Schemes in Organic Electroluminescent Devices Using Terbium Complexes Prepared by Vacuum Evaporation Method (진공 증착법에 의한 Terbium Comp1exes를 이용한 유기 전기 발광 소자의 에너지 밴드에 관한 연구)

  • 표상우;김옥병;이한성;최돈수;이승희
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1999.05a
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    • pp.582-588
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    • 1999
  • 정보화 사회의 발전과 함께 멀티미디어에 대한 관심이 집중되고 있으며, 점유 공간이 작고 가벼우며 대면적이 가능한 정보 표시 디스플레이에 대한 기술은 고부가가치 산업으로 인식되어 지고 있다. 이러한 정보 표시 디스플레이들 중, 전기 발광 소자 (Electroluminescence Display : ELD), 액정 표시 디스플레이 (Liquid Crystal Display LCD), 플라즈마 디스플레이 (Plasma Display Panel) 등의 대한 연구가 세계적으로 매우 활발하게 진행되고 있다. 본 연구에서는 란탄 계열의 금속 착 화합물인 Tb(ACAC)$_3$(Phen)과 Tb(ACAC)$_3$(Phen-Cl)를 이용해 다비이스를 제작한후 광학적 및 전기적 특성을 조사하였다. 또한 luminous efficiency와 cyclic voltametric 방법을 이용해 에너지 밴드로 두 발광 물질인 Tb(ACAC)$_3$(Phen)과 Tb(ACAC)$_3$(Phen-Cl)을 비교.분석하였다. 본 연구의 디바이스 구조를 보면 anode/hole transporting layer (HTL)/emitting material layer (EML)/electron transporting layer (ETL)/cathode와 같고 ETL를 aluminum-tris- (8-hydroxyquinoline) (Alq$_3$)와 bis(10-hydroxybenzo(h)quinolinato)beryllium (Bebq$_2$)를 사용하였으며 HTL 로 N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD)를 사용하였다.

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Impedance Spectroscopy of ${\pi}$-Conjugated Organic Materials

  • Kim, Seong-Hyun;Chu, Hye-Yong;Zyung, Taeh-Young;Yang, Yong-Suk
    • ETRI Journal
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    • v.26 no.2
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    • pp.161-166
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    • 2004
  • AC electrical properties of organic light-emitting diodes with poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene) (MEH-PPV), poly[2,5-bia(dimethyloctylsilyl)-1,4-phenylenevinylene] (BDMOS-PPV), and tris-(8-hydroxyquinolate)-aluminum $(AlQ_3)$ as light-emitting materials are studied. The frequency-dependent real and imaginary parts of impedance were fitted using an equivalent circuit. We found that the conduction mechanism is a space-charge limited current with exponential trap distribution.

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Analysis for Series Resistance of Amorphous Silicon Thin Film Transistor (비정질 실리코 박막 트랜지스터의 직렬 저항에 관한 분석)

  • Kim, Youn-Sang;Lee, Seong-Kyu;Han, Min-Koo
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.43 no.6
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    • pp.951-957
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    • 1994
  • We present a new model for the series resistance of inverted-staggered amorphous silicon (a-Si) thin film transistors (TFT's) by employing the current spreading under the source and the drain contacts as well as the space charge limited current model. The calculated results based on our model have been in good agreements with the measured data over a wide range of applied voltage, gate-to-source and gate-to-drain overlap length, channel length, and operating temperature. Our model shows that the contribution of the series resistances to the current-voltage (I-V) characteristics of the a-Si TFT in the linear regime is more significant at low drain and high gate voltages, for short channel and small overlap length, and at low operating temperature, which have been verified successfully by the experimental measurements.

Carrier Lfetime and Anormal Cnduction Penomena in Silicon Epitaxial Layer-substrate Junction (Epitaxial에 의한 Si epi층의 케리어 수명과 P-N접합의 이상전도현상)

  • 성영권;민남기;김승배
    • 전기의세계
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    • v.26 no.5
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    • pp.83-89
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    • 1977
  • This paper described the minority carrier lifetime in Si epitaxial layer, and also the voltage (V) versus current (I) characteristics of high resistivity Si epitaxial layer0substrate junction. The measured lifetime in Si epi-layer was much shorter than in bulk, and the temperature dependence of lifetime was found to agree well with Shockley-Read model of recombination which applies to high resistivity n-type materials. The V-I curve showed; an ohmic region (I.var.V), a sublinear region (I.var.V$^{1}$2/), a space charge limited current region (I.var.V$^{2}$), and finally a negative resistance region. We investigated these phenomena by the theory of the relaxation semiconductor.

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