Electronic and Vibrational Properties of On-Surface Synthesized Gulf-Edged Chiral Graphene Nanoribbons

Abstract

On-surface synthesis enables the fabrication of graphene nanoribbons (GNRs) with atomic precision, allowing their electronic, optical, and magnetic properties to be tuned by engineering edge structure and width. Progress on the synthesis of chiral GNRs has nevertheless remained limited, largely because existing precursor designs rely on laterally fused acene units and cannot access edge topologies beyond armchair and zigzag. Here, we introduce a new on-surface synthesis motif that yields a gulf-edged chiral GNR. The growth steps are monitored by scanning probe microscopy, and the atomic structure is confirmed by non-contact atomic force microscopy. Scanning tunneling spectroscopy combined with theoretical simulations identifies the gulf-edged chiral GNR as a closed-shell semiconductor with a bandgap of 1.8 eV. Raman spectroscopy reveals vibrational properties, including a distinctive mode that may serve as a fingerprint for chiral GNRs. The Raman analysis further uncovers ambient instability despite the large bandgap and non-spin-polarized edges, consistent with prior reports linking GNR stability to zigzag edge features. This work establishes a rationally designed synthesis motif for chiral GNRs and provides a combined structural, electronic, and vibrational characterization, offering guidelines for future synthesis strategies.