Formation of Thin Polyacrylonitrile Films and Their Electrical Properties

Abstract

Semi- and photo-conductive thin films of polyacrylonitrile with the thickness of a few microns of less are prepared by the silent electric discharge in acrylonitrile monomer vapor followed by the heat-treatment at temperatures of 150°C to 500°C. The growth rate of the films deposited under the discharge is proportional to the monomer vapor pressure and the discharge voltage. The electrical resistivity and its activation energy decrease and the spectral responses of both the photocurrent and the optical absorption shift toward longer wavelength as the heat-treatment temperature rises. Non-ohmic characteristics of the electrical conduction are observed in the filed higher than ∼3×104 V/cm, and agree with the theoretical expression of the modified Pool-Frenkel effect. The energy depth of the trap estimated from the thermally stimulated current measurement is ∼0.5 eV.