Evolution of Electronic Localization in Bottom-up Graphene Nanoribbon Heterojunctions

Graphene nanoribbons (GNRs) are narrow semiconducting strips of graphene that are predicted to exhibit novel electronic and magnetic properties. Recent advances in bottom-up synthesis techniques have enabled atomically-precise control over GNR structure and dopant integration, thus allowing fabrication of a variety of different GNR heterojunctions. The ability to reliably fabricate and characterize GNR heterojunctions is a critical first step in the development of sophisticated future device architectures that incorporate bottom-up GNRs. Using scanning tunneling microscopy (STM) and spectroscopy (STS), we have investigated how GNR heterojunction band edge alignment evolves as a function of heterojunction length. We find that a minimum heterojunction length is required to observe electron localization to one side of the of GNR heterojunction interface, and that increased electronic localization is observed as the heterojunction length increases.