Wide Range Control of the Chemical Composition and Optical Properties of Propanethiol Plasma Polymer Films by Regulating the Deposition Temperature

This work reports about the significant impact of the substrate temperature (T-S) on the chemical composition, bond structure, and refractive index of propanethiol plasma polymers. The experiments are conducted for a T-S range (30-120 degrees C) related to the inherent heating observed during plasma polymerization processes. This highlights the importance of defining T-S in order to reach a real control over the deposition process. Stabilizing T-S is essential to establish a good correlation between the plasma chemistry and the chemical composition of the films. This allows the identification of some of the plasma species responsible for the high sulfur content reached under certain growth conditions (S>40%). This knowledge provides an ample control over the refractive index which is tuned within a wide range (1.63-1.82).