A Predictive Model for Monolayer-Selective Metal-Mediated MoS2 Exfoliation Incorporating Electrostatics

The metal-mediated exfoliation (MME) method enables monolayer-selectiveexfoliation of van der Waals (vdW) crystals, improving the efficacy of largemonolayer production. Previous physical models explainingmonolayer-selective MME propose that the main contributors tomonolayer-selectivity are vdW crystal/metal surface binding energy and/orvdW crystal layer strain resulting from lattice mismatch. However, theperformance of some metals for MME is inconsistent with these models.Here, a new model is proposed using MoS2as a representative vdW crystal.The model explains how the MoS2/metal interface electrostatics, incombination with strain, determines monolayer-selectivity of MME bymodulating the MoS2interlayer energy. Monolayer MoS2/metal interfaces arecharacterized using in situ Raman spectroscopy and density functional theorycalculations to estimate the electrostatics and strain of MoS2in contact withdifferent metals. The model successfully demonstrates the dependence ofMME monolayer-selectivity on the MoS2/metal interface electrostatics andhighlights the significance of electrostatics in nanomaterial vdW interactions.