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Tunable Metallicity in Graphene Nanoribbons Enabled by Five-Membered Rings

ORAL

Abstract

The tunable electronic properties of graphene nanoribbons (GNRs) make them promising candidates for future nanoelectronic devices. Incorporating non-hexagonal rings (e.g., 5-membered rings) into GNRs provides one useful route for tuning their behavior, but the hydrogen termination of such “ring dopants” also plays a role.

Here we report the on-surface synthesis of GNRs featuring 5-membered rings arranged in a zigzag ladder configuration. Synthesis of the GNRs was performed using a molecule-based bottom-up approach that ensures atomically-precise structural control. Density functional theory (DFT) predictions suggest that this GNR could be either a metal (for "hydrogen poor" GNRs) or an insulator (for "hydrogen rich" GNRs) depending on the precise hydrogen termination of the 5-membered rings. Our initial scanning tunneling microscopy (STM) measurements indicate that the pristine GNR is insulating, suggesting that it is in the insulating “hydrogen rich” configuration.

We find that by applying controlled voltage pulses to the GNR with the STM tip we can selectively remove hydrogen atoms, placing the GNR into a conducting “hydrogen poor” state and effectively activating metallic bands. STM spectroscopy and DFT calculations of the electronic density of states show good agreement before and after hydrogen removal, confirming that this process induces metallicity.

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Presenters

  • Ziyi Wang

    University of California, Berkeley

Authors

  • Ziyi Wang

    University of California, Berkeley

  • Kaitlin Slicker

    University of California, Berkeley

  • Weichen Tang

    University of California, Berkeley, Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory

  • Boyu Qie

    University of California, Berkeley

  • Yudi Huang

    University of California, Berkeley

  • Xinheng Li

    University of California, Berkeley

  • Steven G Louie

    University of California, Berkeley, University of California, Berkeley and Lawrence Berkeley National Lab, University of California, Berkeley and Lawrence Berkeley National Laboratory, Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory, Department of Physics, University of California at Berkeley, Berkeley, CA, USA and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

  • Felix R Fischer

    University of California, Berkeley

  • Michael F Crommie

    University of California, Berkeley