Fabrication of graphene nanoribbons/organic molecules interface

The formation and orientation of graphene nanoribbons (GNRs) during on-surface synthesis, as well as their interaction with organic molecules, remain areas of active investigation. Here, we study the growth of 15-carbon-wide armchair graphene nanoribbons (15-AGNRs) from dibromo-p-pentaphenyl (DBPPP) precursors on Au(111) and the subsequent adsorption of pentacene (5P) using low-temperature (~77K) scanning tunneling microscopy. By systematically tracking the transformation from precursor assemblies to polymer intermediates and final nanoribbons, we show that the herringbone reconstruction of the Au(111) substrate imprints a directional preference at the precursor stage, which is preserved through the polymer phase and ultimately manifested in the final ribbon orientations. We further demonstrate that pentacene adsorption on 15-AGNRs is governed primarily by the anisotropic geometry of the ribbons rather than the metallic substrate. These results provide a unified picture of orientation evolution during GNR growth and highlight the role of nanostructure geometry in directing molecular organization at hybrid organic-carbon interfaces.