Band Depopulation of Graphene Nanoribbons Induced by Chemical Gating with Amino Groups.

Li, Jingcheng; Brandimarte, Pedro; Vilas-Varela, Manuel; Merino-Díez, Nestor; Moreno, Cesar; Mugarza, Aitor; Mollejo, Jaime Sáez; Sánchez-Portal, Daniel et al. · ACS Nano · 2020

basic_science · Level V

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Abstract

The electronic properties of graphene nanoribbons (GNRs) can be precisely tuned by chemical doping. Here we demonstrate that amino (NH<sub>2</sub>) functional groups attached at the edges of chiral GNRs (chGNRs) can efficiently gate the chGNRs and lead to the valence band (VB) depopulation on a metallic surface. The NH<sub>2</sub>-doped chGNRs are grown by on-surface synthesis on Au(111) using functionalized bianthracene precursors. Scanning tunneling spectroscopy resolves that the NH<sub>2</sub> groups significantly upshift the bands of chGNRs, causing the Fermi level crossing of the VB onset of chGNRs. Through density functional theory simulations we confirm that the hole-doping behavior is due to an upward shift of the bands induced by the edge NH<sub>2</sub> groups.