Electrical properties of C sub(22)-quinolinium(TCNQ) and polyamic acid alkylamine salts Langmuir-Blodgett films

• Published in: Thin solid films Vol. 331; no. 1-2; pp. 8 - 14
• Main Authors: Kim, Tae Wan, Lee, Ho-Sik, Byun, Dae-Hyun, Kang, Dou-Yol
• Format: Journal Article
• Language: English
• Published: 15.10.1998
• ISSN: 0040-6090

Electrical properties of C sub(22)-quinolinium(TCNQ) and polyamic acid alkylamine salts Langmuir-Blodgett (LB) films have been investigate through a study of surface pressure ( pi )-area (A) isotherms, current-voltage(I-V) characteristics, frequency-dependent dielectric responses, and thermally-stimulated currents (TSC). Through-plane I-V characteristics of C sub(22)-quinolinium(TCNQ) LB films show an anomalous behavior of breakdown near the electric-field strength of 10 super(6) V/cm. Frequency-dependent dielectric constants of the thermally annealed C sub(22)-quinolinium(TCNQ) LB films show that there are two characteristic dispersions in a frequency range of 10-13 Hz; one is a dispersion occurring near 1 MHz coming from the orientational polarization of the molecules and the other is probably due to an interfacial polarization below 1 kHz when the annealing temperature is above 80 degree C. The annealing temperature-dependent dielectric constants of the C sub(22)-quinolinium(TCNQ) LB films show that there are two maximum; one at near 80 degree C and the other at near 180 degree C. The first peak seems to be related to a disorder of alkyl chains. In the I-V characteristics of Z-type polyamic acid alkylamine salts (PAAS) LB films measured along the through-plane at room temperature, ohmic conduction has been observed below around 10 super(5) V/cm, which is similar to that of C sub(22)-quinolinium(TCNQ) LB films. Non-ohmic conduction has been observed above around 10 super(5) V /cm and the conduction mechanism can be explained by Schottky effect. Frequency-dependent dielectric responses of the PAAS LB film show that there is a dispersion at 10 super(4) Hz when the annealing temperature reaches about 100 degree C. Measurements of thermally-stimulated currents of those LB films were performed from room temperature to about 250 degree C and the temperature was increased at a rate of 0.2 degree C/s linearly. TSC peaks are observed at about 70 degree C in the arachidic acid LB films, and at about 70 and 160 degree C in the PAAS LB films. They indicate that the peak at 70 degree C is resulted from the alkyl group, and the other peak at 160 degree C is probably due to C-O group in PAAS molecules.