• Title/Summary/Keyword: Negative Capacitance

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Electrical Characteristics of Carbon Nanotube Embedded 4H-SiC MOS Capacitors (탄소나노튜브를 첨가한 4H-SiC MOS 캐패시터의 전기적 특성)

  • Lee, Taeseop;Koo, Sang-Mo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.27 no.9
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    • pp.547-550
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    • 2014
  • In this study, the electrical characteristics of the nickel (Ni)/carbon nanotube (CNT)/$SiO_2$ structures were investigated in order to analyze the mechanism of CNT in MOS device structures. We fabricated 4H-SiC MOS capacitors with or without CNTs. CNT was dispersed by isopropyl alcohol. The capacitance-voltage (C-V) and current-voltage (I-V) are characterized. Both devices were measured by Keithley 4200 SCS. The experimental flatband voltage ($V_{FB}$) shift was positive. Near-interface trap charge density ($N_{it}$) and negative oxide trap charge density ($N_{ox}$) value of CNT embedded MOS capacitors was less than that values of reference samples. Also, the leakage current of CNT embedded MOS capacitors is higher than reference samples. It has been found that its oxide quality is related to charge carriers and/or defect states in the interface of MOS capacitors.

A study of rear surface passivation by $Al_2O_3$ thin film for ultra thin silicon solar cells (초박형 태양전지를 위한 후면 패시베이션 막의 특성 연구)

  • Park, Sung-Eun;Kim, Young-Do;Tark, Sung-Ju;Kang, Min-Gu;Kwon, Soon-Woo;Yoon, Se-Wang;Kim, Dong-Hwan
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.94-94
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    • 2009
  • 최근 실리콘 태양전지는 점점 얇아 지는 추세에 있다. 실리콘 태양전지에 있어 실리콘의 두께를 감소시키는 것은 실리콘 소모량을 줄이는데 있어 필수적인 조건이 되었다. 이에 따라 실리콘 표면의 passivation도 더욱 중요하게 여겨지고 있다. 실리콘 태양전지의 passivation막의 한 종류인 $Al_2O_3$는 다른 산화막 물질들과는 달리 negative fixed charge를 가지고 있고 charge의 양이 다른 산화막의 density보다 높아 p-type 실리콘의 경우 후면 passivation막으로 이용이 고려되고 있다. 본 연구에서는 atomic layer deposition으로 $Al_2O_3$막을 실리콘 위에 증착하여 열처리에 따른 그 특성을 비교하고 태양전지를 제작하였다. $Al_2O_3$막을 rapid thermal annealing을 통해 서로 다른 분위기에서 열처리 한 결과를 capacitance-voltage를 통해 측정하여 비교, 분석하였고 ellipsomety 분석을 통해 광학적 특성을 비교하였다. 또한 열처리 온도의 변화에 따른 $Al_2O_3$내에 charge에 변화가 있다는 것을 관찰하였다. 이러한 charge의 변화가 태양전지의 passivation에 영향을 주는지 관찰하기 위해 Quasi-steady state photoconductace를 통해 lifetime의 변화를 관찰 하였다. 이러한 실험결과로부터 열처리 분위기와 온도를 최적화 하여 태양전지 passivation 특성을 증가시킬 수 있었다.

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Low-Voltage Operating N-type Organic Field-Effect Transistors by Charge Injection Engineering of Polymer Semiconductors and Bi-Layered Gate Dielectrics (N형 고분자 반도체의 전하주입 특성 향상을 통한 저전압 유기전계효과트랜지스터 특성 연구)

  • Moon, Ji-Hoon;Baeg, Kang-Jun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.30 no.10
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    • pp.665-671
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    • 2017
  • Herein, we report the fabrication of low-voltage N-type organic field-effect transistors by using high capacitance fluorinated polymer gate dielectrics such as P(VDF-TrFE), P(VDF-TrFE-CTFE), and P(VDF-TrFE-CFE). Electron-withdrawing functional groups in PVDF-based polymers typically cause the depletion of negative charge carriers and a high contact resistance in N-channel organic semiconductors. Therefore, we incorporated intermediate layers of a low-k polymerto prevent the formation of a direct interface between PVDF-based gate insulators and the semiconducting active layer. Consequently, electron depletion is inhibited, and the high charge resistance between the semiconductor and source/drain electrodes is remarkably improved by the in corporation of solution-processed charge injection layers.

Electrically Enhanced Readout System for a High-Frequency CMOS-MEMS Resonator

  • Uranga, Arantxa;Verd, Jaume;Lopez, Joan Lluis;Teva, Jordi;Torres, Francesc;Giner, Joan Josep;Murillo, Gonzalo;Abadal, Gabriel;Barniol, Nuria
    • ETRI Journal
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    • v.31 no.4
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    • pp.478-480
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    • 2009
  • The design of a CMOS clamped-clamped beam resonator along with a full custom integrated differential amplifier, monolithically fabricated with a commercial 0.35 ${\mu}m$ CMOS technology, is presented. The implemented amplifier, which minimizes the negative effect of the parasitic capacitance, enhances the electrical MEMS characterization, obtaining a $48{\times}10^8$ resonant frequency-quality factor product ($Q{\times}f_{res}$) in air conditions, which is quite competitive in comparison with existing CMOS-MEMS resonators.

Semiconductor Behavior of Passive Films Formed on Cr with Various Additive Elements

  • Tsuchiya, Hiroaki;Fujimoto, Shinji;Shibata, Toshio
    • Corrosion Science and Technology
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    • v.2 no.1
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    • pp.7-11
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    • 2003
  • Photoelectrochemical response and electrochemical impedance behavior was investigated for passive film formed on sputter-deposited Cr alloy in $0.1kmol{\cdot}m^{-3}$. Photoelectrochemical action spectrum could be separated into two components, which were considered to be derived from $Cr_2O_3$ ($E_g\sim3.6eV$) and $ Cr(OH)_3 $ ($E_g\sim2.5eV$). The band gap energy, $E_g$, of each component was almost constant for various applied potentials. polarization periods and alloying additives. The photoelectrochemical response showed negative photo current for most potentials in the passive region. Therefore, the photo current apparently exhibited p-typesemiconductor behavior. On the other hand, Mort-Schottky plot of the capacitance showed positive slope, which means that passive film formed on Cr alloy has n-type semiconductor property. These apparently conflicting results are rationally explained assuming that the passive film on Cr alloy formed in the acid solution has n-type semiconductor property with a fairly deep donor level in the band gap and forms an accumulation layer in the most of potential region in the passive state.

Switching Dynamics Analysis by Various Models of Hf0.5Zr0.5O2 Ferroelectric Thin Films (Hf0.5Zr0.5O2 강유전체 박막의 다양한 분극 스위칭 모델에 의한 동역학 분석)

  • Ahn, Seung-Eon
    • Korean Journal of Materials Research
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    • v.30 no.2
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    • pp.99-104
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    • 2020
  • Recent discoveries of ferroelectric properties in ultrathin doped hafnium oxide (HfO2) have led to the expectation that HfO2 could overcome the shortcomings of perovskite materials and be applied to electron devices such as Fe-Random access memory (RAM), ferroelectric tunnel junction (FTJ) and negative capacitance field effect transistor (NC-FET) device. As research on hafnium oxide ferroelectrics accelerates, several models to analyze the polarization switching characteristics of hafnium oxide ferroelectrics have been proposed from the domain or energy point of view. However, there is still a lack of in-depth consideration of models that can fully express the polarization switching properties of ferroelectrics. In this paper, a Zr-doped HfO2 thin film based metal-ferroelectric-metal (MFM) capacitor was implemented and the polarization switching dynamics, along with the ferroelectric characteristics, of the device were analyzed. In addition, a study was conducted to propose an applicable model of HfO2-based MFM capacitors by applying various ferroelectric switching characteristics models.

Surface Characteristics of Tool Steel Machined Using Micro-EDM

  • Anwar, Mohammed Muntakim;San, Wong Yoke;Rahman, Mustafizur
    • International Journal of Precision Engineering and Manufacturing
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    • v.9 no.4
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    • pp.74-78
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    • 2008
  • High-speed tool steels are extensively used in tooling industries for manufacturing cutting tools, forming tools, and rolls. Electrical discharge machining (EDM) has been found to be an effective process for machining these extremely hard and difficult-to-cut materials. Extensive research has been conducted to identify the optimum machining parameters for EDM with different tool steels. This paper presents a fundamental study of the surface characteristics of SKH-51 tool steel machined by micro-EDM, with particular focus on obtaining a better surface finish. An RC pulse generator was used to obtain a better surface finish as it produces fine discharge craters. The main operating parameters studied were the gap voltage and the capacitance while the resistance and other gap control parameters were kept constant. A negative tungsten electrode was used in this study. The micro-EDM performance was analyzed by atomic force microscopy to determine the average surface roughness and the distance between the highest peak and lowest valley. The topography of the machined surface was observed using a scanning electron microscope and a digital optical microscope.

A 12.5-Gb/s Optical Transmitter Using an Auto-power and -modulation Control

  • Oh, Won-Seok;Park, Kang-Yeob;Im, Young-Min;Kim, Hwe-Kyung
    • Journal of the Optical Society of Korea
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    • v.13 no.4
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    • pp.434-438
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    • 2009
  • In this paper, a 12.5-Gb/s optical transmitter is implemented using 0.13-${\mu}m$ CMOS technology. The optical transmitter that we constructed compensates temperature effects of VCSEL (Vertical cavity surface emitting laser) using auto-power control (APC) and auto-modulation control (AMC). An external monitoring photodiode (MPD) detects optical power and modulation. The proposed APC and AMC demonstrate 5$\sim$20-mA of bias-current control and 5$\sim$20-mA of modulation-current control, respectively. To enhance the bandwidth of the optical transmitter, an active feedback amplifier with negative capacitance compensation is exploited. The whole chip consumes only 140.4-mW of DC power at a single 1.8-V supply under the maximum modulation and bias currents, and occupies the area of 1280-${\mu}m$ by 330-${\mu}m$ excluding bonding pads.

Correlations between Electrical Properties and Process Parameters of Silicon Nitride Films Prepared by Low Temperature (100℃) Catalytic CVD

  • Noh, Se Myoung;Hong, Wan-Shick
    • Journal of the Korean Ceramic Society
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    • v.52 no.3
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    • pp.209-214
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    • 2015
  • Silicon nitride films were deposited at $100^{\circ}C$ by using the catalytic chemical vapor deposition technique. The source gas mixing ratio, $R_N=[NH_3]/[SiH_4]$, was varied from 10 to 30, and the hydrogen dilution ratio, $R_H=[H_2]/[SiH_4]$, was varied from 20 to 100. The breakdown field strength reached a maximum value at $R_N=20$ and $R_H=20$, whereas the resistivity decreased in the same sample. The relative permittivity had a positive correlation with the breakdown field strength. The capacitance-voltage threshold curve showed an asymmetric hysteresis loop, which became more squared as $R_H$ increased. The width of the hysteresis window showed a negative correlation with the slope of the transition region, implying that the combined effect of $R_N$ and $R_H$ overides the interface defects while creating charge storage sites in the bulk region.

Electrical Properties of Multilayer Chip Varistors in the Response Surface Analysis (반응표면분석법에 의한 적층 칩 바리스터의 전기적 특성)

  • Yoon, Jung-Rag;Jeong, Tae-Seok;Choi, Keun-Mook;Lee, Seok-Weon
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.20 no.6
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    • pp.496-501
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    • 2007
  • In order to enhance sintering characteristics on the $ZnO-Pr_6O_{11}$ based multilayer chip varistors (MLVs), a response surface analysis using central composite design method were carried out. As a result, varistor voltage($V_{1mA}$), nonlinear coefficient ($\alpha$), leakage current ($I_L$) and capacitance (C) were considered to be mainly affected by sintered temperature and holding time. MLVs sintered at $1200^{\circ}C$ and above $1200^{\circ}C$ revealed poor electrical characteristics, possibly due to the reaction between electrode materials(Pd) and $ZnO-Pr_6O_{11}$ based ceramics. On the sintering temperature range $1150{\sim}1175^{\circ}C$, nonlinear coefficient ($\alpha$) and leakage current ($I_L$) were shown to be $60{\sim}69$ and below $0.3{\mu}A$, respectively. In particular, MLVs sintered at $1175^{\circ}C$, 1.5 hr and $2^{\circ}C/hr$ (cooling speed) showed stable ESD(Electrical Static Discharge) characteristics under the condition of 10 times at 8 Kv with deviation varistor voltage, and deviation nonlinear coefficient were 0.3% and 0.33% (at positive), 0.55% (at negative), respectively.