Monitoring chemical vapour deposition of pyrocarbon by electron spin resonance

Pyrolytic carbon films were deposited on boron nitride substrates during plug-flow of a methane/argon gas mixture through a hot-wall tubular reactor at 100 kPa and 1100°C. Of particular interest is the time resolved development of chemical reactions within the free reactor volume, which is projected to the formed structures along the reactor axis. Spatially resolved electron spin resonance (ESR) is used to characterize the deposited films. The width and asymmetry of the ESR line varies monotonously along the reactor axis by more than one order of magnitude within 25 mm.