On-Surface Synthesis of Variable Bandgap Nanoporous Graphene

Dingguan Wang National University of Singapore


Tuning the bandgap of nanoporous graphene is desirable for applications such as the charge transport layer in organic-hybrid devices. The holy grail in the field is the ability to synthesize 2D nanoporous graphene with variable pore sizes, and hence tuneable band gaps. Herein, we demonstrate the on-surface synthesis of nanoporous graphene with variable bandgaps. Two types of nanoporous graphene were synthesized via hierarchical C-C coupling, and verified by low-temperature scanning tunneling microscopy and non-contact atomic force microscopy with CO-terminated tip. Nanoporous graphene-1 is non-planar, and nanoporous graphene-2 is a single-atom thick planar sheet. Scanning tunneling spectroscopy measurements reveal that nanoporous graphene-2 has a bandgap of 3.8 eV, while nanoporous graphene-1 has a larger bandgap of 5.0 eV. Corroborated by first-principles calculations, we propose that the large bandgap opening is governed by the confinement of π-electrons induced by pore generation or the non-planar structure, and can be explained by Clar sextet theory. Our finding shows that by introducing nanopores, semimetallic graphene is converted into semiconducting nanoporous graphene-2 or insulating wide-bandgap nanoporous graphene-1.


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Supplementary material

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