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.