Ultrathin Polymer Film Capacitor Composed of Poly(N-alkylacrylamide) Langmuir−Blodgett Films

The capacitor properties of N -alkylacrylamide polymer Langmuir−Blodgett (LB) films were investigated as a function of number of layers with current−voltage measurement and ac impedance spectroscopy. Poly( N -dodecylacrylamide) (pDDA), poly( N - tert -pentylacrylamide) (ptPA), and poly( N -adamantylacrylamide) (pADA) were used as dielectric materials. The breakdown voltage of the LB films increased linearly with the number of layers. The breakdown electric fields were determined to be 0.27, 0.20, and 0.09 GV/m for pDDA, ptPA, and pADA, respectively. The large capacitance value of 1 μF/cm 2 is obtained at ptPA LB film capacitor with five layers (5.0 nm). The relative dielectric constants for ptPA, pADA, and pDDA are determined to be 5.7, 5.1, and 4.1, respectively, from ac impedance spectroscopy. The dielectric properties are found to be related with a relative ratio of highly polarized amide part to the alkyl side chain length of N -alkylacrylamide polymers.