Perfluorooctane Sulfonyl Fluoride as an Initiator in Hot-Filament Chemical Vapor Deposition of Fluorocarbon Thin Films

We have demonstrated the successful use of an initiator species in hot-filament chemical vapor deposition (HFCVD) of poly(tetrafluoroethylene) thin films from the precursor hexafluoropropylene oxide (HFPO). The introduction of perfluorooctane sulfonyl fluoride (PFOSF) in small concentrations allows the enhancement of deposition rates and increased control over film composition. Endcapping by CF 3 groups is possible, which may provide benefits such as enhanced thermal stability and higher hydrophobicity for HFCVD films. Conversion of the PFOSF is high, and HFPO utilization efficiency can be increased significantly. The generation of an initiator radical via the pyrolysis of PFOSF may contribute to enhanced nucleation rates during film growth. Initiation and/or nucleation is rate-limiting at low filament temperatures, and mass transport limitations dominate at higher filament temperatures.