Correlation between mechanical, optical and chemical properties of thin films deposited by PECVD

Plasma-polymerized films of vinyltriethoxysilane were prepared by plasma-enhanced chemical vapor deposition using an RF (13.56 MHz) helical coupling plasma system operated in a pulsed regime. Thin films deposited under the same deposition conditions but with different thicknesses (9.5 nm–10.5 µm) were analyzed with respect to mechanical, optical, and chemical properties.All the films exhibited a layered structure. The overlayer at the film surface with a thickness (0.9–34 nm) dependent on the sample thickness was revealed by AFM, nanoindentation, and ellipsometry. A gradient behavior of the refractive index and the Young's modulus within the overlayer was related to the surface morphology of the films. A gradient interlayer at the substrate was also discussed.