Abstract
The high-field currents in poly-p-xylylene (PPX) thin films have an anode metal dependence and a negative temperature dependence. They are accompanied by electroluminescence. They are explained in terms of hole injection from anode metal and collision ionization (or electronic avalanche). The authors attempted and discussed the improvement of insulation thin films by chemical or physical modifications. Especially, ozone oxidation much effectively suppressed highfield current.
In this paper, the authors discussed the mechanisms of high-field current and breakdown of PPX thin films using ozone oxidation layer. High-field currents in PPX-oxPPX thin films were suppressed depending on the oxidation time and the position of an oxidation layer above 4 MV/cm at room temperature and above around 3 MV/cm in the low temperature region. High-field currents inoxPPX thin films were more strongly suppressed than those in PPX-oxPPX thin films. We applied a single-electron collision-ionization theory to the breakdown properties of PPX, PPX-oxPPX and oxPPX thin films. Our experimental results are almost consistent with the theory. It is clear from the theory that the mean free path in PPX thin film is longer than that in PPX-oxPPX thin film and that the mean free path in oxPPX at -160°C is longer than that at room temperature. These experimental results are explained by the suppression of collision ionization due to carrier scattering caused by polar groups (C=0) or lattice vibration.
