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

Abstract

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 °C as a transition temperature from the α-form to the β1-form. This structure transition is accompanied by a modification on the DC-conduction mechanisms from ionic to electronic conduction in the α-form and the β1-form, respectively. The AC conduction mechanism is governed by the small polaron tunneling mechanism (SPTM) with WH,α = 0.23 eV and a tunneling distance of 7.71 Å in the α-form, while it becomes a correlated barrier-hopping (CBH) mechanism with a WM,β1 = 0.52 eV in the β1-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 (βKWW) confirms the existence of the transition phase on the parylene N in the vicinity of the 230 °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.