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Nano Research

Article Title

Chevron-type graphene nanoribbons with a reduced energy band gap: Solution synthesis, scanning tunneling microscopy and electrical characterization

Authors

Ximeng Liu, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana–Champaign, Urbana, IL 61801, USA Department of Electrical and Computer Engineering, University of Illinois at Urbana–Champaign, Urbana, IL 61801, USA
Gang Li, Department of Chemistry, University of Nebraska–Lincoln, Lincoln, NE 68588, USA
Alexey Lipatov, Department of Chemistry, University of Nebraska–Lincoln, Lincoln, NE 68588, USA
Tao Sun, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana–Champaign, Urbana, IL 61801, USA Department of Mechanical Science and Engineering, University of Illinois at Urbana–Champaign, Urbana, IL 61801, USA
Mohammad Mehdi Pour, Department of Chemistry, University of Nebraska–Lincoln, Lincoln, NE 68588, USA
Narayana R. Aluru, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana–Champaign, Urbana, IL 61801, USA Department of Mechanical Science and Engineering, University of Illinois at Urbana–Champaign, Urbana, IL 61801, USA
Joseph W. Lyding, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana–Champaign, Urbana, IL 61801, USA Department of Electrical and Computer Engineering, University of Illinois at Urbana–Champaign, Urbana, IL 61801, USA
Alexander Sinitskii, Department of Chemistry, University of Nebraska–Lincoln, Lincoln, NE 68588, USA Nebraska Center for Materials and Nanoscience, University of Nebraska–Lincoln, Lincoln, NE 68588, USA

Keywords

graphene nanoribbons, bottom-up synthesis, electronic structure, dry contact transfer, scanning tunneling microscopy, scanning tunneling spectroscopy

Abstract

Graphene nanoribbons (GNRs) attract a growing interest due to their tunable physical properties and promise for device applications. A variety of atomically precise GNRs have recently been synthesized by on-surface and solution approaches. While on-surface GNRs can be conveniently visualized by scanning tunneling microscopy (STM), and their electronic structure can be probed by scanning tunneling spectroscopy (STS), such characterization remains a great challenge for the solution-synthesized GNRs. Here, we report solution synthesis and detailed STM/STS characterization of atomically precise GNRs with a meandering shape that are structurally related to chevron GNRs but have a reduced energy band gap. The ribbons were synthesized by Ni0-mediated Yamamoto polymerization of specially designed molecular precursors using triflates as the leaving groups and oxidative cyclodehydrogenation of the resulting polymers using Scholl reaction. The ribbons were deposited onto III-V semiconducting InAs(110) substrates by a dry contact transfer technique. High-resolution STM/STS characterization not only confirmed the GNR geometry, but also revealed details of electronic structure including energy states, electronic band gap, as well as the spatial distribution of the local density of states. The experimental STS band gap of GNRs is about 2 eV, which is very close to 2.35 eV predicted by the density functional theory simulations with GW correction, indicating a weak screening effect of InAs(110) substrate. Furthermore, several aspects of GNR-InAs(110) substrate interactions were also probed and analyzed, including GNR tunable transparency, alignment to the substrate, and manipulations of GNR position by the STM tip. The weak interaction between the GNRs and the InAs(110) surface makes InAs(110) an ideal substrate for investigating the intrinsic properties of GNRs. Because of the reduced energy band gap of these ribbons, the GNR thin films exhibit appreciably high electrical conductivity and on/off ratios of about 10 in field-effect transistor measurements, suggesting their promise for device applications.

Graphical Abstract

Publisher

Tsinghua University Press

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