Graphene nanoribbons (GNRs) with widths of a few nanometers are promising candidates for future nanoelectronic applications due to their structurally tunable bandgaps, ultrahigh carrier mobilities, and exceptional stability. However, the direct growth of micrometer-long GNRs on insulating substrates, which is essential for the fabrication of nanoelectronic devices, remains an immense challenge. Here, a scalable single-step synthesis of micrometer-long GNRs on insulating atomically flat hexagonal boron nitride (h-BN) surfaces via nanoparticle-catalyzed chemical vapor deposition is reported.

Ultranarrow (average width of 2 nm) GNRs with lengths of up to 10 μm are synthesized. Molecular dynamics simulations support the experimental results and reveal a van der Waals sliding of the GNRs on the h-BN substrate throughout the growth stage. This study opens a route to explore the performance of high-quality GNR devices and the fundamental physics of 1D moiré superlattices.