Quadrupole-mass-spectroscopy studies on hot filament chemical vapor deposition of carbon films with nano-sized constituents

We used a quadrupole mass spectrometer (QMS) to investigate the dissociation of source gases and the variation of the gas-pahse precursors during the HFCVD process. Since the HFCVD pressure was about 30 Torr, a capillary was installed to sample the gas from the HFCVD chamber while maintaining the QMS at high vacuum. An investigation of the systematic variations in mass spectra corresponding to the increase of methane concentration in the ammonia-free feed gases revealed substantial generation of species containing two carbon atoms. However, an increase of ammonia concentration in the feed gas with 20% of methane resulted in generation of nitrogen containing radicals such as CN and HCN together with the suppression of two-carbon radicals. An implication of observed mass-spectrum variation for the growth behavior of carbon nanotube (CNT) and/or carbon nanoparticle (CNP) films was discussed.