Nano-structural Characterizations: Elongation of Graphene Layers within Solid Hydrocarbons

Nano-structural characterizations of solid hydrocarbons were explained during their formation by the laser ablation technique and during the heat treatment. For the hydrogenated amorphous carbon (HAC), these characterizations cover the hydrogen content, the sp3 and sp2 hybridization, the band gap energy, and the length of the graphene layers. In the atomic and electronic structure
of HAC, the hydrogen to carbon and sp3 to sp2 ratios were characterized through the C-H stretching vibration in the mid-IR band at around the 2924 cm-1. An increase in the optical band gap energy and in the length of the graphene layers in a nano-sized scale was observed with the laser power. After heat treatments of HAC, hydrogen content, sp3/sp2 ratio and the band gap decrease while the average length of the graphene layers increases. Higher laser power shows elongation of the graphene layers in the hydrogen-rich HAC while heat treatments show this in the hydrogen-poor HAC.