• Title/Summary/Keyword: Frequency-dependent electrical properties

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Frequency-dependent electrical properties of $C_22$ -quinolinium(TCNQ) langmuir-blodgett films (C$_22$ -quinolinium(TCNQ) LB막의 주파수에 따른 전기적 특성)

  • 김태완;이상국;신동명;강도열
    • Electrical & Electronic Materials
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    • v.8 no.2
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    • pp.151-157
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    • 1995
  • Frequency-dependent electrical properties of $C_{22}$-Quinolinium(TCNQ) LB films were investigated in a frequency range of 10[Hz]-13[MHz] along a perpendicular direction. The films were heat-treated to understand an electrodynamic response in a temperature range of 20-240[.deg. C]. Frequencydependent dielectric constants show that there are two characteristic dispersions; one is a dispersion occuring near 1[MHz] coming from the orientational polarization of the molecules and the other one is an interfacial polarization effect below 1[kHz] or so when the annealing temperature is above 80 [.deg. C]. The overall frequency-dependent dielectric constant is higher near 80[.deg. C]. It may be due to a softness of the alkyl chains. Several other methods were employed to identify the internal structure change of the films. DSC(differential scanning calorimetry) data of the $C_{22}$-Quinolinium(TCNQ) molecules shows that there is an endothermic process near 110[.deg. C] and a weak exothermic process near 180[.deg. C]. While the endothermic process is related to a disordering of the alkyl chains, the exothermic process seems to be due to a chemical structure change of the TCNQ molecules. Thickness measurement by ellipsometry shows that there is a thickness drop near 100[.deg. C], and the thickness above 120[.deg. C] becomes around 20[%] of the room-temperature value.lue.

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Optical and electrical properties of $C_{22}$-quinolinium(TCNQ) langmuir-glodgett films depending on the annealing temperatures ($C_{22}$-quinolinium(TCNQ) langmuir-blodgett 박막의 열처리 온도에 따른 광학적 및 유전특성)

  • 홍언식;유덕선;김태완
    • Electrical & Electronic Materials
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    • v.8 no.4
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    • pp.458-463
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    • 1995
  • The optical and electrical properties of $C_{22}$-Quinolinium(TCNQ) Langmuir-Blodgett films have been studied depending on the annealing temperatures. The optimal properties were investigated using UV/visible(300-800[nm]) absorption spectra and FTIR(Fourier-transformed- infrared) absorption measurements. The electrical properties were investigated in a frequency range of 10[Hz]-13[MHz]. The UV/visible absorption spectra at room temperature show that there are four characteristic peaks at 320, 380, 494 and 678[nm]. These absorption peaks decrease very rapidly above the annealing temperature of 180[.deg. C], which is due to a structural change of TCNQ. The FTIR absorption measurements strongly support the result of the UV/visible absorption spectra, because the absorption peak of TCNQ- at 2181[$cm^{-1}$ /] also decreases above 140[.deg. C]. The frequency-dependent dielectric constant shows that there is a dielectric dispersion near 1[MHz] which is due to an orientational polarization of the molecules inside the film. The overall frequency-dependent dielectric constant is higher near 80[.deg. C]. It may be due to a softness of the alkyl chains.s.

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Frequency Dependent Properties of Tris(8-Hydroxyquinoline) Aluminum Thin Films

  • Lee, Yong-Soo;Park, Jae-Hoon;Choi, Jong-Sun
    • KIEE International Transactions on Electrophysics and Applications
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    • v.11C no.3
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    • pp.70-74
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    • 2001
  • Admittance or impedance spectroscopy is one of the powerful tools to study dielectric relaxation and loss processes in organic and inorganic materials. In this study, the frequency dependent properties of an indium tin oxide/tris(8-hydroxyquinoline) aluminum($Alq_3$)/aluminum structure have been studied. The conductance of the $Alq_3$ film increases with the DC applied voltage up to 4V and decreases above 4V in the low frequency region. This indicates that the resistance of the device decreases with the applied bias due to the carrier injection enhancement, thereafter the injected carriers form the space charge and the additional injection of carriers is prevented. The Cole-Cole plot of the admittance takes a one-semicircle shape, which means that the device can be modeled as a parallel resistor-capacitor network. The resistance and capacitance were estimated as 8.62k${\Omega}$ and 2.7nF, respectively, at 3V in the low frequency region. The dielectric constant ( ${\epsilon}'$ ) of the $Alq_3$ film is independent of the frequency in the low frequency region below 100kHz, while the frequency dependency was observed at above 100kHz. The dielectric loss factor ( ${\epsilon}"$ ) of the $Alq_3$ film shows the dielectric dispersion below 100kHz and dielectric absorption in higher frequency domain. The dispersion is thought to be related to the hopping process of the carriers. The ${\epsilon}"$ is proportional to the reciprocal of the frequency. The dielectric relaxation time was extracted to about 0.318${\mu}s$ from the dielectric absorption spectrum.

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Study on the Ferroelectric Properties of ALD-HfO2 in Microwave Band for Tunable RF Apparatus (Tunable RF 기기 적용을 위한 ALD-HfO2의 마이크로파 대역 강유전체 특성 고찰)

  • Han, Sang-Woo;Lee, Chang-Hyun;Lee, Jeong-Hae;Cha, Ho-Young
    • Journal of IKEEE
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    • v.22 no.3
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    • pp.780-785
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    • 2018
  • In this work, We investigated the frequency-dependent capacitance tunability of a metal-ferroelectric-metal variable capacitor fabricated using ALD $HfO_2$ ferroelectric material. The capacitance of the MFM capacitor could be tuned as a function of the bias voltage, up to the microwave frequency range. We observed a capacitance tuning range of ~3 % up to 2.5 GHz, proving the feasibility of the use of ALD $HfO_2$ in the microwave frequency band.

Electrical Properties of ZnO-SnO$_2$ Composites (ZnO-SnO$_2$복합체의 전기적성질)

  • 김태원;전장배;최우성
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1996.11a
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    • pp.303-305
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    • 1996
  • The electrical Properties of ZnO added TiO$_2$were investigated by using the complex impedance measurement and voltage-current source and measurement unit. The electrical conductivity of ZnO added TiO$_2$decrease with increasing the content of ZnO. The frequency-dependent Ac conductivity increase as frequency increase. Also, the trend of capacitances is similar to the AC conductivity. The semicircles of impedance spectrum increase with increasing ZnO contents. The decrease of electrical conductivity seems to be the effect of ZnO acceptor adding.

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Blue Electroluminescent Properties and Dependent of Dye Mixed ratio of ZnS:Cu (ZnS:Cu의 청색 발광 특성과 염료 혼합비 의존성)

  • 이종찬;박대희
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.11a
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    • pp.528-531
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    • 2000
  • ZnS:Cu phosphor used on powder electroluminescent device has a green emission in low frequency and a blue emission in high frequency. In this paper, to obtain the powder electroluminescent device of the blue emission in low frequency, the emission properties with mixed the ratio between phosphor and dye was investigated. The mixed ratio of the dye was from 0 to 5 weight percent. To inquire into the blue emission, the emission spectrum, the CIE coordinate system and the brightness were measured.

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Impedance Spectroscopy Study of TiO$_2$ added SnO$_2$ (TiO$_2$가 첨가된 SnO$_2$의 Impedance Spectroscopy에대한 연구)

  • 최우성;박춘배
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1996.05a
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    • pp.277-279
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    • 1996
  • A.C. and D.C. characteristic of TiO$_2$ added SnO$_2$ are investigated to study the electrical properties. The electrical inductivity increases as TiO$_2$content increase. The doer effect of TiO$_2$ is crucial role for the increase of electrical conductivity. The frequency-dependent ac inductivity increases with the increase of TiO$_2$ contents at low frequency region. However, at high frequency region, the difference of ac conductivity is very small. Impedance spectrums are consist of the one semicircle. Therefore, the sizes of semicircle decreases with increasing the TiO$_2$ contents.

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The Electrical Characterization and Relaxation Behavior of Ag(Ta0.8Nb0.2)O3 Ceramics

  • Kim, Young-Sung;Kim, Jae-Chul;Jeong, Tae-Hoon;Nam, Sung-Pill;Lee, Seung-Hwan;Kim, Hong-Ki;Lee, Ku-Tak
    • Transactions on Electrical and Electronic Materials
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    • v.15 no.2
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    • pp.100-102
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    • 2014
  • $Ag(Ta,Nb)O_3$ materials have a perovskite structure with a low loss tangent. These materials have been widely researched for their applications as high-frequency, passive components. Also, $Ag(Ta,Nb)O_3$ materials have weak frequency dispersion with high dielectric permittivity which gives them enormous potential for use in electronic components, including the filters, and embedded capacitors. Therefore, our research will discuss the structural and electrical relaxation properties of $Ag(Ta_{0.8}Nb_{0.2})O_3$ ceramics for device applications. We will investigate using X-ray diffraction to understand their structural properties and will analyze voltage dependent leakage current and timedependent relaxation behavior to understand their material properties.

Stabilization of the Perovskite Phase and Electrical Properties of Ferroelectrics in the Pb2(Sc,Nb)O6 System

  • Kim, Yeon Jung
    • Applied Science and Convergence Technology
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    • v.24 no.6
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    • pp.224-227
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    • 2015
  • Ferroelectric $Pb_2(Sc,Nb)O_6$ were prepared under two different sintering conditions using the oxide mixing method and the electrical properties were measured. The sintering conditions were $1350^{\circ}C$ for 25 minutes and $1400^{\circ}C$ for 20 minutes. EDX spectroscopy and XRD were used to determine the crystalline characteristic of the $Pb_2(Sc,Nb)O_6$ compositions Pyrochlore phase showed about 2% in all $Pb_2(Sc,Nb)O_6$ specimens. It expands the growth of crystals in samples sintered at $1400^{\circ}C$ than $1350^{\circ}C$, but all samples were the optimal crystallization. The temperature and frequency dependence of the complex dielectric constant and admittance were measured to analyze the electrical properties. The high dielectric constant of the specimens reflects the good stoichiometry and crystallization. The maximum value of the dielectric constant in the two specimens treated with sintering at $1350^{\circ}C$ and $1400^{\circ}C$ were more than 27,000, and the dielectric loss at room temperature is smaller than 0.05. The maximum dielectric constant decreased with increasing frequency, the transition temperature also increased in $Pb_2(Sc,Nb)O_6$ compositions. The admittance and susceptance values reach a peak at all temperatures, and the magnitude of the peak increases with increasing measuring temperature. Strong frequency dependent of maximum admittance, susceptance, dielectric constant and dielectric loss were observed.

Voltage and frequency dependent electrical properties in organic light-emitting diodes of $ITO/Alq_{3}/Al$ ($ITO/Alq_{3}/Al$의 유기 발광 소자에서 바이어스 전압과 주파수에 따른 전기적 특성)

  • Chung, Dong-Hoe;Kim, Sang-Keol;Hur, Sung-Woo;Kim, Kwang-Jip;Song, Min-Jong;Hong, Jin-Woong;Lee, Joon-Ung;Kim, Tae-Wan
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.04a
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    • pp.115-118
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    • 2003
  • Complex impedances with frequency and voltage variation were analyzed in $ITO/Alq_{3}/Al$(100nm)/Al device structure. At low frequency, complex impedance is mostly expressed by resistive component, and at the high frequency by capacitive component. Also, we have evaluated resistance, capacitance and permittivity.

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