Synthesis of carbon nanotubes over Fe catalyst on aluminium and suggested growth mechanism

Abstract

Carbon nanotubes (CNTs) have been grown by the decomposition of C 2H 2 over a thin catalyst film in order to investigate the growth mechanism of CNTs by chemical vapour deposition (CVD). The catalyst was prepared from an iron nitrate precursor solution that was spin-coated on an aluminium substrate. The density (mg cm −2) and the length of the CNTs were greatly influenced by the precursor concentration, the time of deposition, the temperature and the ratio of C 2H 2:N 2. Scanning and transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction measurements have been carried out in order to investigate the behaviour of the catalyst before and during the growth process. The iron nitrate film formed an amorphous iron oxide layer that transformed to crystalline Fe 2O 3, which was reduced to Fe 3O 4 and FeO in contact with the C 2H 2: N 2 reaction atmosphere. The CNTs synthesis took place on small iron carbide (Fe 3C) particles that were formed from the FeO.