Temperature-mediated growth of helical polymer and chevron-type graphene nanoribbon from internally fluorinated precursor on Au(111)

Abstract

Graphene nanoribbons (GNRs) of precise size and shape, critical for controlling electronic properties and future device applications, can be realized via precision synthesis on surfaces using rationally designed molecular precursors. Fluorine-bearing precursors have the potential to form GNRs on a nonmetallic substrate favorable for device fabrication. Here we investigate the temperature-mediated growth of a new fluorine-bearing precursor 6,11-diiodo-1,4-bis(2-fluorophenyl)-2,3-diphenyltriphenylene (C₄₂H­₂₄F₂I₂) into helical polymer intermediates and chevron-type GNRs on Au(111) by combining scanning tunneling microscopy, X-ray photoelectron spectroscopy, and ab initio density functional theory simulations. The fluorinated precursors do not adsorb on the Au(111) surface at lower temperatures, necessitating an optimum substrate temperature to achieve maximum possible polymer and GNR lengths. We compare the adsorption behavior with that of the pristine chevron precursors and discuss the effects of C-H and C-F bonds. The results will help elucidate the growth mechanism of GNRs with fluorine-bearing precursors and establish a foundation for future synthesis of GNRs on nonmetallic substrates.