RESUMEN
Graphene nanoribbons (GNRs) have attracted strong interest from researchers worldwide, as they constitute an emerging class of quantum-designed materials. The major challenges toward their exploitation in electronic applications include reliable contacting, complicated by their small size (<50 nm), and the preservation of their physical properties upon device integration. In this combined experimental and theoretical study, we report on the quantum dot behavior of atomically precise GNRs integrated in a device geometry. The devices consist of a film of aligned five-atom-wide GNRs (5-AGNRs) transferred onto graphene electrodes with a sub 5 nm nanogap. We demonstrate that these narrow-bandgap 5-AGNRs exhibit metal-like behavior at room temperature and single-electron transistor behavior for temperatures below 150 K. By performing spectroscopy of the molecular levels at 13 K, we obtain addition energies in the range of 200-300 meV. DFT calculations predict comparable addition energies and reveal the presence of two electronic states within the bandgap of infinite ribbons when the finite length of the 5-AGNR is accounted for. By demonstrating the preservation of the 5-AGNRs' molecular levels upon device integration, as demonstrated by transport spectroscopy, our study provides a critical step forward in the realization of more exotic GNR-based nanoelectronic devices.
RESUMEN
In graphene nanoribbons (GNRs), the lateral confinement of charge carriers opens a band gap, the key feature that enables novel graphene-based electronics. Despite great progress, reliable and reproducible fabrication of single-ribbon field-effect transistors (FETs) is still a challenge, impeding the understanding of the charge transport. Here, we present reproducible fabrication of armchair GNR-FETs based on networks of nanoribbons and analyze the charge transport mechanism using nine-atom wide and, in particular, five-atom-wide GNRs with large conductivity. We show formation of reliable Ohmic contacts and a yield of functional FETs close to unity by lamination of GNRs to electrodes. Modeling the charge transport in the networks reveals that transport is governed by inter-ribbon hopping mediated by nuclear tunneling, with a hopping length comparable to the physical GNR length. Overcoming the challenge of low-yield single-ribbon transistors by the networks and identifying the corresponding charge transport mechanism is a key step forward for functionalization of GNRs.
RESUMEN
Bottom-up synthesis of low-bandgap graphene nanoribbons with various widths is of great importance for their applications in electronic and optoelectronic devices. Here we demonstrate a synthesis of N = 5 armchair graphene nanoribbons (5-AGNRs) and their lateral fusion into wider AGNRs, by a chemical vapor deposition method. The efficient formation of 10- and 15-AGNRs is revealed by a combination of different spectroscopic methods, including Raman and UV-vis-near-infrared spectroscopy as well as by scanning tunneling microscopy. The degree of fusion and thus the optical and electronic properties of the resulting GNRs can be controlled by the annealing temperature, providing GNR films with optical absorptions up to â¼2250 nm.
