Characterization of carbon CVD coatings near atmospheric deposition pressure

Pyrolytic carbon coatings show excellent hermetic properties and can be applied to optical fibers during the draw process by thermally activated chemical vapor deposition (CVD). This study investigates the relationship between carbon growth rates, microstructure, and deposition conditions at 600 torr chamber pressure. The films are grown from methane, propane and butane precursors on stationary 3 mm quartz rods. Hydrocarbon precursor gas concentrations are varied between 10% and 100% in N2, and surface temperatures are varied between 800 and 1500°C. X-Ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), and Secondary Ion Mass Spectroscopy (SIMS) are used to determine the film composition, and to inspect for a SiC transition layer between the carbon and the glass. The carbon films are analyzed for thickness, carbon phase, and surface roughness using ESEM and Raman Spectroscopy.