Dielectric and Conduction Mechanisms of Parylene N at High Temperature: Phase-Transition Effect

Dielectric and electrical properties correlated with the structure analysis have been studied on 27% semicrystalline parylene-N (-H2C-C6H4-CH2-)(n) thin films. Transition-phase, AC- and DC-conduction mechanisms, and the MW-interfacial polarization were identified in parylene N at high temperature by experimental and theoretical investigations. The dielectric analysis based on the dc conductivity highlights a temperature of 230 degrees C as a transition temperature from the alpha-form to the beta(1)-form. This structure transition is accompanied by a modification on the DC conduction mechanisms from ionic to electronic conduction in the alpha-form and the beta(1)-form, respectively. The AC conduction mechanism is governed by the small polaron tunneling mechanism (SPTM) with W-H,W-alpha = 0.23 eV and a tunneling distance of 7.71 angstrom in the alpha-form, while it becomes a correlated barrier-hopping (CBH) mechanism with a W-M,W-beta = 0.52 eV in the beta(1)-form. The imaginary part of the electrical modulus formalism obeys the Kohlrausch-Williams-Watt (KWW) model and shows the presence of the interfacial polarization effect. The theoretical Kohlrausch exponent (beta(KWW)) confirms the existence of the transition phase on the parylene N in the vicinity of the 230 degrees C as deduced by the DC- and the AC-conduction parameters. The correlations between the experimental results and the theoretical models are very useful knowledge and tools for diverse parylene N applications at high temperature.