Gas chromatography study of reagent degradation during chemical vapor deposition of carbon nanotubes.

The high temperature decomposition of three types of hydrocarbons, such as ethanol, camphor and cyclohexanol has been studied in order to determine the role played by the molecular structure of the precursor during the formation of carbon nanotubes (CNTs) catalyzed by ferrocene. This investigation will help in identifying the properties of the carbon precursor crucial to obtain the highest CNT selectivity and quality. A gas chromatography mass spectrometry (GC/MS) technique was employed to monitor the evolution of the volatile thermal degradation products exhausted after a growth process of CNTs run at 900 degrees C in Ar atmosphere. The presence of ferrocene catalyst has shown negligible effect on the composition of the volatile products and the main decomposition molecule detected was benzene. Furthermore, the comparison of GC/MS results with scanning electron microscopy images and Raman spectra of the as-grown samples have suggested that the presence of benzene and its interaction with the iron clusters play a key role in the CNT formation, but only on the bare silicon wafer.