Transmission electron microscopy study of carbon nanostructures grown by MPACVD in CH4/CO2 gas mixture

In this paper we present some results obtained from transmission electron microscopy, selected area electron diffraction patterns and the electron energy loss spectroscopy of carbon nanostructures (CNSs) obtained by microwave plasma assisted chemical vapour deposition (MPACVD) in the CH4/CO2 gas mixture. The experiments are carried out at a substrate temperature around 900 deg C. The Fe catalyst is silicon supported and dispersed into an amorphous silicon oxide (SiO). It is found that the formation of various CNSs occurs when varying the discharge parameters such as multiwalls carbon nanotubes (MWCNTs), carbon nanowalls, and carbon nanotips. Different behaviour of carbon nanotips is obtained. Their morphology and electronic structure are studied, and a growth mechanism depending on atomic oxygen etching of CNSs is discussed.