Research Progress in On-Surface Synthesis of Graphene Nanoribbons: Tuning Electrical Properties via Intercalation Strategy

Graphene nanoribbons (GNRs) are quasi-one-dimensional derivatives of graphene that exhibit width- and edge-dependent bandgaps arising from quantum confinement, making them highly attractive building blocks for next-generation nanoelectronic and optoelectronic devices. The advent of on-surface bottom-up synthesis has enabled the fabrication of atomically precise GNRs with well-defined widths, edge topologies, and heterostructures, providing unprecedented control over their electronic properties. However, these syntheses are typically carried out on metallic substrates, such as Au(111), Ag(111), and Cu(111), whose strong electronic coupling, screening effects, and substrate-induced charge transfer obscure the intrinsic electronic structure of the nanoribbons and limit their direct application. To address this challenge, intercalation of atomically thin dielectric or semiconducting layers beneath pre-synthesized GNRs has emerged as a powerful strategy to electronically decouple the nanoribbons from the underlying metal while preserving their structural integrity. This approach not only enables direct access to the near-intrinsic electronic properties of GNRs, but also offers a versatile means of engineering interfacial charge transfer, band alignment, and local electrostatic environments. In this review, we summarize recent advances in the intercalation of diverse adlayers underneath GNRs, with particular emphasis on in-situ structural characterization, intercalation mechanisms, and the resulting modulation of electronic properties. We conclude by discussing current challenges and future opportunities for exploiting intercalation as a general platform for tailoring GNR-based van der Waals heterostructures and device architectures.