Nitrogen admixture effects on growth characteristics and properties of carbon nanowalls

Abstract

The plasma functionalization of carbon nanowalls (CNWs) is of great interest due to their potential applications in electron field emission and energy storage devices. In this study, the effects of nitrogen on the growth and properties of CNWs are thoroughly investigated by varying a wide range of the N2 concentrations in the CH4/H2/N2 discharge plasma. Nitrogen-doped carbon nanowalls (NCNWs) were synthesized in a single-step growth using the hydrogen radical injection plasma-enhanced chemical vapor deposition technique. The formation of dense NCNWs was found to be enhanced by nitrogen and was three times higher in the sample with a 150 sccm N2 flow rate than in the sample without N2 addition (N-0). As the N2 concentration increased from 0 to 200 sccm, the morphology of CNWs changed from relatively straight to curly-like nanowall structures. A high-resolution optical emission spectroscopic observation shows that as N2 flow increased, CN radicals became the dominant species, suppressing the formation of C2 and CH. Photoelectron spectroscopy analysis revealed the nitrogen doping effect on graphene layers at high N2 concentrations. According to Raman and Transmission Electron Microscopy analyses, the NCNWs had more branched and thicker nanowalls with higher defect concentrations than the N-0 sample. The wettability of NCNWs was improved, particularly for the sample with a N2 flow rate of 150 sccm.