Ultra-narrow-gate single-electron transistors based on crossed graphene nanoribbons

Abstract Graphene nanoribbons (GNRs) are promising candidates for next-generation nanoelectronics owing to their width-dependent bandgaps and high carrier mobility. However, integrating ultra-narrow GNRs into well-defined device architectures with local electrostatic control remains challenging. Here, we demonstrate a dual-gate single-electron transistor (SET) device consisting of two spatially isolated, in-situ encapsulated GNRs grown within hexagonal boron nitride (hBN) flakes, where one GNR serves as the transport channel and the other as an ultra-narrow local top gate, enabling nanoscale electrostatic modulation. Room-temperature transport measurements show that the GNR channel operates as a field-effect transistor with an on/off ratio of ${\sim} 2 \times 10^{3}$ ∼ 2 × 10 3 and a subthreshold swing of 150 mV⋅dec −1 under back-gate control, while the GNR top gate provides comparable electrostatic control despite its much shorter gate length, validating its role as an efficient local gate. At 15 K, the device exhibits clear single-electron transport characteristics, including periodic Coulomb blockade (CB) oscillations and gate-tunable Coulomb diamonds. Upon tuning the gate voltages, the transport behavior evolves continuously from Coulomb blockade to Fabry–Pérot interference, revealing a crossover from localized charge transport to coherent interference governed by the locally modulated potential landscape. Our results establish in-situ encapsulated GNRs as a promising platform for carbon-based nanoelectronics and for exploring one-dimensional quantum transport in locally gated nanostructures.