• 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.

• 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.