Selectablity of mechanical and dielectric properties of Parylene-C columnar microfibrous thin films by varying deposition angle

Columnar microfibrous thin films (μFTFs) were fabricated with a collimated flux of Parylene-C monomers directed at an angle χ_v∈{ 30 °, 52 °, 60 °, 67 °, 80 °, 90 °}with respect to the substrate plane in a vacuum chamber. The porosity of the columnar μFTFs was found to decrease with the deposition angle v c and lie between 0.38 and 0.56. Both the static Young's modulus and the yield strength of the columnar μFTFs were found to be higher in the morphologically significant plane than in the plane normal to it. In both loading directions, static Young's moduli and yield strengths are about two orders of magnitude lower for the columnar μFTFs than the corresponding parameters of the bulk material, making the columnar μFTFs softer. The lowest relative permittivity of the fabricated columnar μFTFs in the 1-1000 kHz range was found to be about 70% of that of the bulk material. The static Young's moduli, yield strengths, and the relative permittivity were correlated to the porosity, crystallinity, and the deposition angle. Both mechanical and dielectric properties of the columnar μFTFs can be controlled by selecting v c appropriately for application in flexible electronics.