Top-down reorganization of self-assembled monolayers on Au(111)

One of the most promising strategies for controlling the bandgap of graphene is bottom-up synthesis of graphene nanoribbons from aryl halide precursors. This synthetic approach forms nanoribbons with well-defined widths and atomically precise edges, which are necessary for ensuring bandgap uniformity. However, neither on-surface nor solution-based graphene nanoribbon synthesis techniques adequately address the problem of positional control, which is crucial to the fabrication of graphene nanoribbon transistors. To better understand this issue, we investigate the on-surface ordering of 10,10'-dibromo-9,9'-bianthracene (DBBA), the 7A-GNR monomer precursor. Scanning tunneling microscopy imaging shows that DBBA molecules spontaneously assemble on Au(111) into non-covalent two-dimensional islands. By varying sample temperature during and after deposition, we observe three different adsorbate arrangements. These two-dimensional packing structures demonstrate differing responses to localized excitations. The difference in packing structures and their respective responses to electro-mechanical disruption can give us insight into how to best optimize conditions for locally controlled and large-scale thermal GNR polymer growth.