Reversible Graphene decoupling by NaCl photo-dissociation

TL;DR

This study demonstrates a reversible method to intercalate sodium under graphene on Ir(111) via photo-dissociation of NaCl, leading to electronic decoupling and doping, with potential applications in graphene-based electronics.

Contribution

It introduces a novel reversible intercalation technique using photo-dissociation of NaCl to control graphene's electronic properties.

Findings

NaCl dissociates under X-ray exposure, releasing Na to intercalate under graphene.

Intercalation causes decoupling of graphene from Ir(111), evidenced by moiré pattern disappearance.

Na intercalation results in n-doped graphene due to charge transfer.

Abstract

We describe the reversible intercalation of Na under graphene on Ir(111) by photo-dissociation of a previously adsorbed NaCl overlayer. After room temperature evaporation, NaCl adsorbs on top of graphene forming a bilayer. With a combination of electron diffraction and photoemission techniques we demonstrate that the NaCl overlayer dissociates upon a short exposure to an X-ray beam. As a result, chlorine desorbs while sodium intercalates under the graphene, inducing an electronic decoupling from the underlying metal. Low energy electron diffraction shows the disappearance of the moir\'e pattern when Na intercalates between graphene and iridium. Analysis of the Na 2p core-level by X-ray photoelectron spectroscopy shows a chemical change from NaCl to metallic buried Na at the graphene/Ir interface. The intercalation-decoupling process leads to a n-doped graphene due to the charge transfer from the Na, as revealed by constant energy angle resolved X-ray photoemission maps. Moreover, the process is reversible by a mild annealing of the samples without damaging the graphene.