Thermal Annealing of Fluorocarbon Films Grown by Hot Filament Chemical Vapor Deposition

Growth of a Surface-Tethered, All-Carbon Backboned Fluoropolymer by Photoactivated Molecular Layer Deposition

The synthesis of an all-carbon backboned fluoropolymer using photoactivated molecular layer deposition (pMLD) is developed. pMLD is a vapor-phase, layer-by-layer, organic thin film synthesis method utilizing UV light, allowing for the creation of materials previously unavailable via thermal MLD. The carbon backbone is achieved by reacting an iodine-containing fluorocarbon monomer (1,4-diiodooctafluorobutane) and a diene monomer (1,5-hexadiene) under UV irradiation in a step-growth polymerization sequence. The polymerization occurs with a growth rate of 1.3 Å/cycle, forming a copolymer containing hydrocarbon and fluorocarbon segments. X-ray photoelectron spectroscopy (XPS) was used to confirm the formation of new carbon-carbon bonds and quantify the final film composition. In situ XPS thermal annealing experiments confirm the film stability up to 400 °C. The ability to pattern the fluoropolymer on a surface is demonstrated using a photomask, suggesting that these films could be incorporated into photolithographic processes. Together, these results demonstrate that pMLD can be used to synthesize carbon backboned films with photopatterning ability, expanding the available chemistries and potential applications of MLD polymers.

25th anniversary article: CVD polymers: a new paradigm for surface modification and device fabrication

Well-adhered, conformal, thin (<100 nm) coatings can easily be obtained by chemical vapor deposition (CVD) for a variety of technological applications. Room temperature modification with functional polymers can be achieved on virtually any substrate: organic, inorganic, rigid, flexible, planar, three-dimensional, dense, or porous. In CVD polymerization, the monomer(s) are delivered to the surface through the vapor phase and then undergo simultaneous polymerization and thin film formation. By eliminating the need to dissolve macromolecules, CVD enables insoluble polymers to be coated and prevents solvent damage to the substrate. CVD film growth proceeds from the substrate up, allowing for interfacial engineering, real-time monitoring, and thickness control. Initiated-CVD shows successful results in terms of rationally designed micro- and nanoengineered materials to control molecular interactions at material surfaces. The success of oxidative-CVD is mainly demonstrated for the deposition of organic conducting and semiconducting polymers.

Carbon nanotube-directed polytetrafluoroethylene crystal growth via initiated chemical vapor deposition

Initiated chemical vapor deposition (iCVD) has been shown to be suitable for blanketing surfaces with thin polymer coatings of ≈1-2 nm and greater. In this work, iCVD coatings of polytetrafluoroethylene (PTFE) deposited on carbon nanotube (CNT)-based surfaces show CNT-templated PTFE single crystal growth. While the coating forms disoriented agglomerates when deposited on an amorphous carbon background, "shish-kebab" structures are observed when grown on single-walled carbon nanotubes (SWCNT) as well as CNT buckypaper. It is shown that the shish-kebab structure is composed of PTFE lamellae arranged with the chain backbones running parallel to the SWCNT axis. This result allows one to control not only the surface chemistry using PTFE but also the coating surface topology.