Flexible cross-linked organosilicon thin films by initiated chemical vapor deposition

Highly cross-linked but flexible polyhexavinyldisiloxane (p-HVDSO) thin films were deposited by initiated chemical vapor deposition (iCVD) for applications where smooth, adhesive, and flexible coatings are required, like biological implantations or thin film electronics. The substrate temperature and the initiator flow rate dependencies were investigated as routes to enhance the cross-linking degree of the network. The most cross-linked film was obtained at substrate temperature of 60°C and monomer/initiator ratio of ∼1. Kinetic analysis of the deposition process indicates that the film formation rate is limited by the saturation reactions of the vinyl groups, with an activation energy of 53.8 kJ/mol with respect to the substrate temperature. Atomic force microscopy showed microscopically flat surfaces, while tape test and bending cycles revealed high adhesion and flexibility. The possibility of obtaining a tunable cross-linking degree through methylene bridges by changing the substrate temperature makes the p-HVDSO films suitable for a wide range of applications.