Thermally stimulated short-circuited current from plasma-polymerized polyacrylonitrile thin film sandwiched between aluminum electrodes

An appreciable amount of thermally stimulated short-circuited current is observed during heating and cooling between 30° and 160 °C from unpoled plasma-polymerized polyacrylonitrile thin film sandwiched between aluminum electrodes (Al-PAN-Al). The observed current is attributed to the space charges accumulated at the vicinity of the outer electrode producing a charge gradient towards the inner. The disorientation of dipoles also contributes to the thermally stimulated current. The temperature activation energy of 1.37 eV indicates that the electrons are trapped at the covalent bond of the carbon atoms. A temperature gradient and surface strain, developed in the sandwiched system on heating when the electrode thicknesses are different, give an additional contribution to the thermally stimulated current. Observations are also made by the application of a positive voltage to the outer electrode, and the relative magnitudes of the various components are discussed.