High Dielectric Strength PlasmaーPolymerized Thin Films.

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The fabrication of plasmaーpolymerized thin films was made by introducing ethylene or trifluoromethane gas into a plasma in argon excited with 13.56MHz. PPE thin films were aged in the vacuum for one hour to avoid the oxidation. PPTFM thin films were not necessary to be aged. The chemical structure was investigated by FT-IR. FT-IR spectra show the existence of some C=0 or -C=C- bonds in PPE thin films. No oxidation was observed in PPTFM thin films manifest high dielectric strength of 8-10 MV/cm at room temperature which is higher than that of chemically polymerized organic films. However, the dielectric strength of PPE films decreases remarkably with humidity. PPTFM films are more stable against humidity than PPE films, though they show the lower dielectric strength than PPE films at dry a condition. Gold electrodes give a larger current in PPE thin films than aluminum electrodes, however, PPTFM thin films show no electrode dependence in the electrical conduction. Besides, the conductivity of PPTFM thin films is one or two orders of magnitude lower than that of PPE thin films. From the practical point of view, the influence of ambient gases on the electrical conduction was investigated. The conductivity of PPE thin films with aluminum electrodes shows about one order of magnitude larger than that measured in a vacuum or in nitrogen. In conclusion, PPE thin films are useful in vacuum because of high dielectric strength, however, films prepared from fluorine gas are desirable because of the chemical stability against oxidation when they are used under the ordinary atmospheric condition.