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

TL;DR

This study demonstrates that amino groups attached to graphene nanoribbons can effectively gate them, causing valence band depopulation and Fermi level shifts, confirmed by experimental and theoretical analysis.

Contribution

It introduces a new chemical doping method using amino groups to tune the electronic properties of graphene nanoribbons.

Findings

NH₂ groups cause significant band up-shift in chGNRs

Fermi level crosses the valence band onset due to doping

Density functional theory confirms hole-doping mechanism

Abstract

The electronic properties of graphene nanoribbons (GNRs) can be precisely tuned by chemical doping. Here we demonstrate that amino (NH$_2$) 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$_2$-doped chGNRs are grown by on-surface synthesis on Au(111) using functionalized bianthracene precursors. Scanning tunneling spectroscopy resolves that the NH$_2$ groups significantly up-shift 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$_2$ groups.