Characterizing Carbon Nanomaterial Thin Films through Atomic Force Microscopy

The unique thermal, electric, and photoelectric properties of carbon nanomaterial thin films, such as graphene nanoribbons (GNRs) and single-walled carbon nanotubes (SWCNTs), make them promising candidates for incorporation into devices for enhanced storage, conversion, and transport of energy-carrying species (e.g. electrons and excitons). An improved understanding of the arrangement of the individual nanoscale carbon atoms into hierarchical structures that determine the long-range morphology will be critical to understanding the fundamental transport processes in electronic devices made from these materials. We present results from atomic force microscopy (AFM) scans to characterize the morphology of GNR thin films synthesized via spray coating and vacuum filtration. Properties such as film roughness and the size of discrete aggregates combined with 4-point conductivity measurements provide important insight into the mechanism of charge carrier transport. We propose that the size and greater surface coverage of discrete aggregates makes GNR thin films different from SWCNT thin films in which straw-like bundles are formed. This implies a difference in charge carrier transport, since there is less empty space within the thin film. We discuss next steps in the project including exploration of conductive AFM scans and chemical doping.