$\alpha$ , $\beta$ , and $\gamma$ relaxation mechanisms have been identified in semicrystalline (45% of crystallinity) parylene-C ${\left(–{\text{H}}_2\text{C}–{\text{C}}_6{\text{H}}_3\text{Cl}–{\text{CH}}_2–\right)}_n$ films. C–Cl bonds induce the $\beta$ -relaxation and explain increase in the dielectric constant as the frequency decreases in usual temperatures of operation for devices incorporating parylene-C. At cryogenic temperature $\left(<-20°\text{C}\right)$ , $\gamma$ -relaxation is assigned to the local motions of phenyl groups. Both $\beta$ and $\gamma$ relaxation processes obey an Arrhenius law with activation energy $E_a\left(\beta \right)=91.7\text{kJ}/\text{mole}$ and $E_a\left(\gamma \right)=8.68\text{kJ}/\text{mole}$ . $\alpha$ -relaxation associated with cooperative segmental motions of the ${\left(–{\text{H}}_2\text{C}–\varnothing –{\text{CH}}_2–\right)}_n$ chains is observed with a peak at ${10}^{-2}\text{Hz}$ for $T=80°\text{C}$ and follows a Vogel–Fulcher–Tamman–Hesse law.

Parylene C (C₈H₇Cl)_n thin films were deposited along the Si(100) index on a p-type Si substrate at room temperature by a vapor deposition polymerization method. The effects of film thickness on the crystalline structure, roughness, dielectric and electrical properties of parylene C films were investigated. X-ray diffraction has confirmed an amorphous structure in thinner films (d < 40 nm ≈ R_g: gyration radius) and a semicrystalline structure in thicker films (d < 40 nm). The roughness (Rms) varied according to a power law depending on the thickness Rms ∼ d^β with β = 0.22 ± 0.05. The effect of the diffusion monomers and chains relaxations in volume are the main factors limiting the evolution of the surface roughness according to film thickness for d < 40 nm and the crystalline size effect for d > 40 nm due to surface energy minimization when the film gets thicker. The dielectric constant increases as a power law according to film thickness ε′ = d^β with β = 0.042 ± 0.04 for d < 1000 nm and 0.0138 ± 0.02 for d > 1000. This is interpreted as caused by the decreasing of voids and discontinuities of the material with increasing film thickness. The leakage current density J suddenly increases with decreasing film thickness especially for d < 1000 nm, referring to a more pronounced amorphous content, but it is practically thickness independent from d > 10 000 nm and it shows a value of a bout 4 × 10⁻⁸ A/m for an applied field of 20 MV/m.