Microstructure of Carbon Film Deposited Using Hot-Filament Chemical Vapor Deposition

Abstract

The microstructure of carbon film, deposited using hot-filament chemical vapor deposition, was investigated in relation to deposition pressure and methane concentration as deposition variables. Methane concentration in hydrogen gas was varied from 0.5 to 5% in volume. Deposition pressures were 5, 15, 45 and 75 Torr. Filament temperature and deposition temperature were fixed at 2100 degrees C and 950 degrees C, respectively. With increasing methane concentration, the surface morphology changed its microstructure from microcrystalline diamond, to nanocrystalline diamond, to graphite. Raman spectroscopic analysis and X-ray diffraction analysis confirmed the bonding structures corresponding to each microstructure. At 5 Torr, the surface showed a fine grained morphology, different from the microstructures in the other pressure cases; however, the bonding nature also changed from diamond to graphite with increasing methane concentration.