A Kinetic Pathway toward Narrowest Zigzag Graphene Nanoribbons Grown on Cu(111)*

Narrowest zigzag graphene nanoribbons (nZGNRs) have advantages over extended graphene in both electronic and magnetic properties. However, the fabrication of nZGNRs via bottom-up approach remains a standing challenge. Here, based on first-principles calculations we propose to grow nZGNRs via self-assembly of 1,4-Dibromo-2,5-Bis(bromomethyl)benzene precursors on Cu(111). We first show that the precursor can be easily adsorbed on Cu(111), accompanied by simultaneous debromination in the bromomethyl groups with energy barriers of ~0.1 eV. The remaining Br atoms are more easily detached than the H atoms of the precursors, with energy barriers of 0.5~0.7 eV, leading to C₈H₆ radicals that are suitable for formation of nZGNRs. Two such radicals can couple to form a nZGNR-like radical dimer with the unsaturated C atoms located on the positions similar to the C₈H₆ radicals at ~573 K, enabling the coalescence of the subsequent C₈H₆ radicals. Furthermore, we show that the nZGNR-like radical dimer is energetically more favorable than most by-product dimers, ensuring a relatively high reaction yield. These findings provide a new route toward fabrication of nZGNRs for various realistic applications in electronics and spintronics.