pi-A isotherms and electrical properties of polyamic acid alkylamine salts (PAAS) Langmuir-Blodgett films

Deposition conditions, surface morphology, and electrical properties of polyamic acid alkylamine salts (PAAS) Langmuir-Blodgett (LB) films have been investigated through a study of surface pressure-area pi-A isotherm, AFM (atomics force microscopy), and current-voltage characteristics. To obtain the optimum conditions of film deposition, the pi-A isotherms were examined by varying temperature, barrier moving speed, dipping speed, spreading amount of solution etc. The Z-type LB films were made at the surface pressure of 5 mN m(-1) and 25 mN m(-1) for the AFM study; the former surface pressure forms the gas phase and the latter one forms the solid phase. The LB films made in the gas phase show domains with a size of about 200 Angstrom diameter and 70 Angstrom height. However, the LB films made in the solid phase show a very smooth surface with 2 Angstrom surface roughness. In the current-voltage characteristics measured along the perpendicular direction of the films, ohmic conduction has been observed below approximate to 10(5) V cm(-1) and the calculated electrical conductivity is about 10(-13) S cm(-1). Nonohmic conduction has been observed above approximate to 10(5) V cm(-1) and the conduction mechanism can be explained by the Schottky effect.