Strain and Piezo-Doping Mismatch between Graphene Layers
Résumé
Modulation of electronic properties of bilayer materials through the strain and doping mismatch between layers opens new opportunities in 2D material straintronics. We present here a new approach allowing to generate asymmetric strain or doping between layers and a method to quantify it using a supported isotopically labeled bilayer graphene studied by in situ Raman spectroscopy. Strain differences up to ∼0.1% between the two graphene layers have been obtained by applying pressures of up to 10 GPa with nonpolar solid environments. However, when immersed in a liquid polar environment, namely, a mixture of ethanol and methanol, a piezo-doping mismatch between layers is observed. This asymmetrical doping increases with pressure, leading to charge concentration differences between layers of the order of 1013 cm–2. Our approach thus allows disentangling strain and doping effects in high-pressure experiments evidencing the asymmetries of these phenomena and comforting isotopic bilayer graphene as a benchmark system for the study of asymmetric effects in devices or composite surfaces.
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