Redox-Governed Charge Doping Dictated by Interfacial Diffusion in Two-Dimensional Materials

Abstract

Controlling extra charge carriers is pivotal in manipulating electronic, optical, and magnetic properties of various two-dimensional (2D) materials. Nonetheless, the ubiquitous hole doping of 2D materials in the air and acids has been controversial in its mechanistic details. Here we show their common origin is an electrochemical reaction driven by redox couples of oxygen and water molecules. Using real-time photoluminescence imaging of WS2 and Raman spectroscopy of graphene, we capture molecular diffusion through the 2D nanoscopic space between 2D materials and hydrophilic substrates, and show that the latter accommodate water molecules also serving as a hydrating solvent. We also demonstrate that HCl-induced doping is governed by dissolved O2 and pH in accordance with the Nernst equation. The nanoscopic electrochemistry anatomized in this work sets an ambient limit to material properties, which is universal to not only 2D but also other forms of materials.

19 pages, 4 figures

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Cited by in corpus (7)

• Strong Second Harmonic Generation from Bilayer Graphene with Symmetry Breaking by Redox-Governed Charge Doping
• In-Plane and Out-of-Plane Excitonic Coupling in 2D Molecular Crystals
• Tunability of electrical and thermoelectrical properties of monolayer MoS${}_2$ through oxygen passivation
• Optically Facet-Resolved Reaction Anisotropy in Two-Dimensional Transition Metal Dichalcogenides
• Optical Imaging of Chemically and Geometrically Controlled Interfacial Diffusion and Redox in 2D van der Waals Space
• Activated Migration of Localized Ligand-Field Excitons in Atomically Thin CrCl3
• Redox and Molecular Diffusion in 2D van der Waals Space