• Electrical & Electronic Materials
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• v.7 no.2
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• pp.138-144
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• 1994

Electrical conduction phenomena of $C_{22}$-quinolium(TCNQ) Langmuir- Blodgett(LB) films are reported through a study of current-voltage(I-V) characteristics along a perpendicular direction. The I-V characteristics were investigated by applying a step or a pulse voltage to the specimen as well as changing temperatures in the range of 20-250[.deg. C] It show an ohmic behavior in low-electric field, and a nonohmic behavior in high-electric field. This nonohmic behavior has been interpreted in terms of a conduction mechanism of space-charge limited current and Schottky effect. When the electric field is near the strength of 10$_{6}$ V/cm, there occur anomalous phenomena similar to breakdown. When step or pulse voltage is applied, the breakdown voltage shifts to the higher one as the step or pulse time width becomes shorter. To see the influence of temperature, current was measured as a function of temperature under the several bias voltages, which are lower than that of breakdown. It shows that the current increases to about 103 times near 60-70[.deg. C], and remains constant for a while up to around 150[.deg. C] and then suddenly drops. We have also performed a DSC(differential scanning calorimetry) measurement with $C_{22}$-quinolium(TCNQ) powder in the range of 30-300[.deg. C]. These results imply that the anomalous phenomena occuring in the high electric field are caused by the electrical and internal thermal effect such as a joule heating.ating.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.77-81
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• 1992

$C_{22}$-Quinolium-TCNQ LB films were deposited on the glass substrates by Langmuir-Blodgett technique at room temperature. Transfer ratios and UV-visible absorption spectra were studied for X, Y and Z-Types. Absorption in Z-Type was higher than X and Y-Types, which indicates a better arrangement in this type. We have also investigated dc electrical conductivities and ac responses along the horizontal and vertical direction to the film surface. As a result, we are able to determine the capacitance of film and the measured horizontal conductivity was about $10^{-7}$~$10^{-8}$ S/cm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.11a
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• pp.137-140
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• 1993

Electrical properties and thermal annealing effects of $C_{22}$-quinolium(TCNQ) Langmuir-Blodgett(LB) films were studied. Typical current-voltage(I-V) characteristics along the perpendicular direction chow an anomalous behavior of breakdown near the electric-field strength of $10^{6}$V/cm. To see the thermal influence of the specimen, current was measured as a function of temperature(20∼$180^{\circ}C$). It shows that the current increases about 4 orders of magnitude near 60∼$70^{\circ}C$ and remains constant far a while up to ∼$150^{\circ}C$ and then suddenly drops. Such increase of current near 60∼$70^{\circ}C$ seems tn be related to a softness of alkyl chains. Besides the electrical measurements, UV/visible absorption(300∼800 nm) of the thermally annealed sample was measured to see the internal-structure change. It is found that there are four characteristic peaks. At 494 nm, the optical absorption of the thermally annealed specimen at $60^{\circ}C$ starts increase and stays almost constant upto∼ $140^{\circ}C$. And eventually it disappears above $180^{\circ}C$. After heat treatment of the specimen up to $150^{\circ}C$, Uv/visible absorption was measured while cooling.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1193-1196
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• 1993

Electrical properties of $C_{22}$-Quinolium(TCNQ) Langmuir-Blodgett(LB) films are reported depending on a type of applied voltage on a type of applied voltage and temperature. A conductivity was identified to be anisotropic with a ratio of ${\sigma}||/{\sigma}{\bot}{\simeq}10^7$ at room temperature. The I-V characteristics along the film surface direction show an ohmic behavior up to a few hundred volts. But the I-V characteristics in the vertical direction display an ohmic behavior for low-electric field, and a nonohmic behavior for high-electric field. This nonohmic behavior has already been interpreted as a conduction mechanism of space-charge limited current and Schottky effect near the electric-field strengh of $10^6$ V/cm. When the electric field exceeds further, there is anormalous phenomia similiar to breakdown. From the study of I-V characteristics with the application of step or pulse voltage, we have found that the breakdown voltage shifts to higher one as the step or pulse interval becomes shorter. These results indicate that the breakdown is due to both electrical and thermal effect. To see the infulence of temperature, current was measured as function of temperature with several bias voltages, which are lower than that of breakdown. It shows that the current increases about 3 orders of magnitude near $60{\sim}70^{circ}C$, and remains constant for a while up to $140^{\circ}C$ and then suddenly drops. Arahidic acid was used to cmpare with $C_{22}$-Quinolium(TCNQ) LB films.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1289-1291
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• 1994

Dielectric properties of $C_{22}$-Quinolium(TCNQ) Langmuir-Blodgett (LB) films were studied as a function of frequency(10Hz-13MHz) and annealing temperature($20{\sim}240^{\circ}C$). A complex dielectric constant ${\epsilon}^*={\epsilon}'-i{\epsilon}"$, in general, shows the frequency dependence of orientational polarization in the measured frequency range. A dielectric permittivity ${\epsilon}'$ at 10Hz is around 8.2 and decreases very slowly as the frequency increases up to 1 MHz, and then suddenly drops above this frequency, while a dielectric loss factor ${\epsilon}"$ reaches a maximum near 1 MHz. Its annealing temperature dependence at 10Hz shows that ${\epsilon}'$ and ${\epsilon}"$ increase as the temperature increases upto $180^{\circ}C$, even though there is a little drop near $120{\sim}160^{\circ}C$. Both ${\epsilon}'$ and ${\epsilon}"$ drop quickly above $180^{\circ}C$. which may be thought of a destruction of the LB films. Another fact of the annealing temperature dependence of the dielectric constant is an occurrence of the new dielectric dispersion below 100Hz. This low frequency dispersion is getting clear above $80^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1991.10a
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• pp.7-9
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• 1991

$\prod$-A characteristics of N-docosylquinolium-TCNQ complex were investigated with the following variations. I> $\prod$-A characteristics with a variation of spreading amount. ii> $\prod$-A characteristics with a variation of barrier speed. iii> $\prod$-A characteristics with a variation of subphase temperature. An optimum surface pressure for a deposition of Langmuir-Blodgett(LB) layer was found to be a 40∼50 mN/m in pure water subphase (pH 5.4, $25^{\circ}C$).

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.864-867
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• 1992

This paper describes optimum conditions for depositing Langumuir Blodgett(LB) films. $\pi$-A isotherm characteristics were studied with the following species, $C_{18}$-Quinolium(TCNQ), $C_{22}$-Quinolium(TCNQ), Azobenzene, Arachidic Acid, by varing length of alkyl chains, temperacture, pH, spreading amount, barrier moving speed and etc. We have observed the change of $\pi$-A isotherm depending on the above variations. From there we investigate the depositing conditions of LB films for each material.

• Electrical & Electronic Materials
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• v.5 no.4
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• pp.411-420
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• 1992

C$_{2+}$-Quinolium(TCNQ) 유기 초박막을 Langmuir-Blodgett 방법을 이용하여 유리기판 위에 누적하였다. 이의 최적 누적조건을 알아보기 위하여 .pi.-A isotherm특성을 온도, pH, 압축 속도, 분산량 등을 변화시키면서 조사하였다. 누적 과정은 전이비를 통하여 고체 기판에 누적되는 정도를 살펴볼 수 있었으며 누적된 박막은 다음과 같은 방법으로 확인하였다. 광학적인 방법으로 광흡수도, 전기적인 방법으로 전기 용량, 그리고 기계적인 방법으로 두께를 직접 측정하여 누적된 박막의 상태를 관찰하였다. 상온에서 이방성 전기 전도도를 측정하였는데 수평 방향으로 ~1 x $10^{-7}$S/cm, 수직 방향으로 ~1 x $10^{-14}$S/cm의 값을 얻었다.