Nanofabrication and properties of the highly oriented carbon nanocones

Abstract

A process to fabricate Co-assisted carbon nanocones (CNCs) was successfully developed by using microwave plasma chemical vapor deposition (MP-CVD). The nanostructures could be manipulated by adjusting the ratios of the source gases (CH4/H-2=5/80-15/80 sccm/sccm) and the substrate bias (0 similar to-300 V). The properties of deposited nanostructures were characterized by field emission scanning electron microscopy (FESEM), Raman Spectroscopy, auger electron spectroscopy (AES) spectra. The results show that the nanostructures with cone shape are resulted from competition between the ion bombardment rate and the growing speed of the nanostructures in the plasma, where ion bombardment is drove by the presence of negative substrate bias. In other words, a higher substrate negative bias (>-150 V) and a lower concentration of carbon species in the plasma are favorable conditions to grow highly oriented CNCs due to a greater ion bombardment energy and lower lateral growth rate of the nanostructures, respectively. The results indicate that CNCs synthesized under the applied bias of -300 V show an excellent performance in field emission current density (up to similar to 173 mA/cm(2) at 10 V/mu m). (c) 2004 Elsevier B.V. All rights reserved.