Ac-conductivity and dielectric relaxations above glass transition temperature for parylene-C thin films

45% semi-crystalline parylene-C (-H2C-C6H3Cl -CH2-)(n) thin films (5.8 mu m) polymers have been investigated by broadband dielectric spectroscopy for temperatures above the glass transition (T-g = 90 degrees C). Good insulating properties of parylene-C were obtained until operating temperatures as high as 200 degrees C. Thus, low-frequency conductivities from 10(-15) to 10(-12) S/cm were obtained for temperatures varying from 90 to 185 degrees C, respectively. This conductivity is at the origin of a significant increase in the dielectric constant at low frequency and at high temperature. As a consequence, Maxwell-Wagner-Sillars (MWS) polarization at the amorphous/crystalline interfaces is put in evidence with activation energy of 1.5 eV. Coupled TGA (Thermogravimetric analysis) and DTA (differential thermal analysis) revealed that the material is stable up to 400 degrees C. This is particularly interesting to integrate this material for new applications as organic field effect transistors (OFETs). Electric conductivity measured at temperatures up to 200 degrees C obeys to the well-known Jonscher law. The plateau observed in the low frequency part of this conductivity is temperaturedependent and follows Arrhenius behavior with activation energy of 0.97 eV (deep traps).