Ultra-narrow metallic armchair graphene nanoribbons

• Published in: Nature communications Vol. 6; no. 1; p. 10177
• Main Authors: Kimouche, Amina, Ervasti, Mikko M, Drost, Robert, Halonen, Simo, Harju, Ari, Joensuu, Pekka M, Sainio, Jani, Liljeroth, Peter
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 14.12.2015
• Subjects: Applied physics; Density functional theory; Electronic structure; Energy gap; Graphene; Low temperature; Microscopy; Nanoelectronics; Nanoribbons; Nanotechnology devices; Polymerization; Scanning tunneling microscopy
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms10177

Graphene nanoribbons (GNRs)-narrow stripes of graphene-have emerged as promising building blocks for nanoelectronic devices. Recent advances in bottom-up synthesis have allowed production of atomically well-defined armchair GNRs with different widths and doping. While all experimentally studied GNRs have exhibited wide bandgaps, theory predicts that every third armchair GNR (widths of N=3m+2, where m is an integer) should be nearly metallic with a very small bandgap. Here, we synthesize the narrowest possible GNR belonging to this family (five carbon atoms wide, N=5). We study the evolution of the electronic bandgap and orbital structure of GNR segments as a function of their length using low-temperature scanning tunnelling microscopy and density-functional theory calculations. Already GNRs with lengths of 5 nm reach almost metallic behaviour with ∼100 meV bandgap. Finally, we show that defects (kinks) in the GNRs do not strongly modify their electronic structure.