Dielectric Investigation of Parylene D Thin Films: Relaxation and Conduction Mechanisms

Abstract

Parylene is a generic name indicating a family of polymers with the basic chemical structure of poly-p-xylylene. Parylene N and Parylene C are the most popular for applications. Curiously, Parylene D (poly( dichloro-p-xylylene), (C8H6Cl2)) was forgotten for applications. This report is the consequence of a later availability of a commercial dimer of Parylene D and also to the recent advent of fluorinated Parylenes allowing extending applications at higher temperatures. In our work, from a dielectric analysis, we present the potentialities of Parylene D for applications particularly interesting for integration in organic field-effect transistors. Dielectric and electrical properties, macromolecular structures, and dynamics interaction with electric field as a function of frequency and temperature are studied in 5.8 μm thick Parylene D grown by chemical vapor deposition. More exactly, the dielectric permittivity, the dissipation factor, the electrical conductivity, and the electric modulus of Parylene D were investigated in a wide temperature and frequency ranges from -140 to +350 °C and from 0.1 Hz to 1 MHz, respectively. According to the temperature dependence of the dielectric permittivity, Parylene D has two different dielectric responses. It is retained as a nonpolar material at very low temperature (like Parylene N) and as a polar material at high temperature (like parylene C). The dissipation factor shows the manifestation of two relaxations mechanisms: γ and β at very low and high temperatures, respectively. The γ relaxation is assigned to the local motions of the C-H end of the chains when the cryogenic temperature range is approached. A broad peak in tan δ is assigned to the β relaxation. It corresponds to rotational motion of some polar C-Cl groups. For temperature above 260 °C a mechanism of Maxwell-Wagner-Sillars polarization at the amorphous/crystalline interfaces was identified with two activation energies of Ea1 = 2.12 eV and Ea2 = 3.8 eV. Moreover, the conductivity and the dielectric permittivity relaxation processes have been discussed in terms of nearly constant loss (NCL) and universal dynamic regime (UDR). Finally, ionic conduction and electrode polarization effects are identified at very high temperatures and their physical origins are discussed.

Conduction and Dielectric Relaxation Mechanisms in Athabasca Oil Sands with Application to Electrical Heating

“…For frequencies higher than f h , the relaxation of the polarization cloud is in-phase with the outer electrical field resulting in short-time ion dynamics characterized by back and forth motion over limited ranges . This total conductivity behavior due to hopping ion transport obeys the well-known universal dielectric response (UDR), namely, Jonscher’s relation. − Oil Sands 1, which has the least amount of water and clays, clearly obeys Jonscher’s relation: where f h indicates hopping frequency corresponding to the conduction relaxation time, σ dc is the limiting value of σ T ′ when ω → 0, and the s parameter depends on temperature, morphology, and composition and should be 0 ≤ s ≤ 1. Following this universal law indicates that conduction in Oil Sands 1 could be a case of ion motion by activated hopping between charge compensating sites. , It can be observed that the hopping frequency f h separating the short-range conduction process (ac conduction) from long-range conduction process (dc conduction) shifts toward the higher frequency regime as we go from Oil Sands 2 to 4 indicating that increasing water and clay content causes dc conduction to dominate.…”

Low‐Energy Room‐Temperature Healing of Cellular Metals

“…The dimer vaporizer was set at 175 °C, the pyrolysis furnace at 700 °C, and the deposition chamber was kept at room temperature (≈25 °C). Detailed information on the deposition process of Parylene D and its polymerization is available in other articles . Parylene D was chosen as a passivating coating because of its excellent chemical stability, high dielectric strength, and superior barrier properties, as well as its favorable failure strain (10%)…”

Study of dielectric relaxation and thermally activated a.c. conduction in lead containing topological glassy semiconductors

“…Due to this feature, lead chalcogenides become a better candidate for a tremendous number of applications. [20][21][22][23][24][25][26][27][28][29] Examples of their potential applications are solar cells , telecommunications, 23 eld effect transistors (FET), 24 and sensitive membrane materials for developing conventional chemical sensors selective to metal ions in liquid media, as well as biological imaging. 25,26 The aim of the present investigation was to study the effect of Se atom replacement by Pb atoms on the electrical properties of a multi-component system.…”