Tip Growth of Quasi-Metallic Bilayer Graphene Nanoribbons with Armchair Chirality

S Lou and B Lyu and JJ Chen and XL Zhou and WW Jiang and L Qiu and PY Shen and SQ Ma and ZC Zhang and YF Xie and ZH Wu and Y Chen and KQ Xu and Q Liang and K Watanabe and T Taniguchi and LD Xian and GY Zhang and WE Ouyang and F Ding and ZW Shi, NANO LETTERS, 24, 156-164 (2023).

DOI: 10.1021/acs.nanolett.3c03534

Graphene nanoribbons (GNRs), quasi one-dimensional (1D) narrow strips of graphene, have shown promise for high-performance nanoelectronics due to their exceptionally high carrier mobility and structurally tunable bandgaps. However, producing chirality-uniform GNRs on insulating substrates remains a big challenge. Here, we report the successful growth of bilayer GNRs with predominantly armchair chirality and ultranarrow widths (<5 nm) on insulating hexagonal boron nitride (h-BN) substrates using chemical vapor deposition (CVD). The growth of GNRs is catalyzed by transition metal nanoparticles, including Fe, Co, and Ni, through a unique tip-growth mechanism. Notably, GNRs catalyzed by Ni exhibit a high purity (97.3%) of armchair chirality. Electron transport measurements indicate that the ultrathin bilayer armchair GNRs exhibit quasi-metallic behavior. This quasi-metallicity is further supported by density functional theory (DFT) calculations, which reveal a significantly reduced bandgap in bilayer armchair GNRs. The chirality- specific GNRs reported here offer promising advancements for the application of graphene in nanoelectronics.

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