Mechanical manipulation of graphene nanoribbons on Au(111) using large amplitude scanning force microscopy experiments and calculations

We investigate the manipulation of weakly bound graphene nanoribbons (GNRs) on the Au(111) surface using large amplitude scanning force microscopy. The GNRs are fabricated via surface-assisted Ullmann coupling. Mobile GNRs are identified in scanning images by increased noise due to their weak binding. Their mobility is reduced when they are part of an extended GNR network. Even during passive imaging, interactions between the tip and the GNR can induce slight movements, allowing us to approximate the corrugation of the surface binding potential. We demonstrate tip-induced rotation and lateral displacement of GNRs perpendicular to their axis, during which the ribbon is partially lifted from the surface. Based on first-principles calculations, we construct a two-dimensional potential energy landscape and perform climbing image nudged elastic band calculations to approximate energy barriers for translation. Both approaches show that the barrier strongly depends on the GNR orientation. In addition, we find that beyond a critical length, GNRs become effectively immobilized due to increased energy barriers and reduced flexibility. The theoretical results align well with the observed outcomes of the manipulation experiments.