The influence of nano sized carbon cover precipitated onto polyimide (PI) surface from electrical discharge medium on the electrophysical properties of dielectric

In this study, the electrophysical properties of polyimide (PI), which is widely used in electrical insulation, microelectromechanical systems, biomedical, optoelectronic and microelectronic technology because of having excellent electrical, thermal, mechanic and chemical properties, are investigated. For this purpose, the electrical properties such as dielectric permittivity, dielectric loss factor and AC conductivity have been calculated by using experimental capacitance (C), loss tangent (D) and conductance (G) values measured in a certain frequency and temperature range by a Metal-Dielectric-Metal (Au-PI-Au) electrode system for a PMDA-ODA type PI sample. Afterwards, three different types of modification processes have been applied to three identical samples. The electrophysical properties of the modified samples have been measured by using the same method, and the samples have been investigated by using scanning electron microscope (SEM). The plot of calculated values for modified samples versus time and frequency have been illustrated and analyzed comparatively. It has been observed that the obtained experimental results have a good agreement with theoretical results obtained by using Havriliak-Negami approach. The activation energy of a chosen sample has been calculated for two different relaxation regions by using Arrhenius equation in order to have any supposition about the conduction mechanism of the sample. Furthermore, dielectric breakdown voltage, volume resistivity and surface resistivity of the sample have been also measured.Finally, it has been concluded that: i) The interfacial polarization and DC conductivity of the sample affect the dielectric behavior of the sample negatively especially in high temperature-low frequency region, ii) The electrical conduction in PI dielectric is achieved mostly by the ion hopping, iii) By considering the improved electrical properties the %5C2H2-%95Ar plasma modification applied to the sample for an hour is agreed as the most efficient modification, while the modification by corona discharge affects the electrical properties negatively.