Synthesis Methods for Graphene

Abstract

Graphene nanoribbons (GNRs) are the complement of nanotubes in graphene nanotechnology. These strips of graphene have a very high length-to-width ratio and usually exhibit semiconducting behavior, which could be an advantage to modern electronic industries. GNRs are categorized as an attractive class of quasi one-dimensional (1D) material that can be fabricated by finite extinction of graphene sheets provided with smooth edges. A significant amount of width-controlled GNR can be synthesized through graphite nanotomy (nanoscalecutting), where graphite nano-structured blocks are turned out by using a sharp diamond knife on graphite, which are then exfoliated to produce corresponding GNR. GNR can also be fabricated by unzipping or cutting open carbon nanotubes (CNTs). In this context, GNRs are produced by plasma etching of multiwalled CNT, which are partially embedded in a polymer film. The resultant nanoribbons have smooth edges and an ultrathin width distribution. In another method, a combination of KMnO and HSO are used to tear the CNT open along a single axis. In the context of this work, a remarkable amount of nonsemiconducting nanoribbons are synthesized. In some recent reports, GNRs are demonstrated to be synthesized onto SiC substrates using ion implantation followed by vacuum or laser annealing of graphene layers. Some other researchers utilized chemical vapor deposition (CVD) on a graphene substrate and nanowire, and GNRs were successfully demonstrated in high density without any trimming, with a top-down patterning process. In this chapter, various schemes of GNR fabrication are demonstrated, and their advantages and limitations are featured in detail.