Optimizing Mechanical Exfoliation of Tungsten Diselenide (WSe2) for Large-Area 2D Flakes

Abstract

Tungsten Diselenide (WSe₂), a transition metal dichalcogenide (TMD) 2D material, is a rising topic among scientists for its ability to exhibit piezoelectricity that can be incorporated into energy harvesting technology. To maximize the potential of WSe₂ for energy harvesting, the material must be a couple of atoms thick—ideally a monolayer. These flakes can be achieved using cost-effective mechanical exfoliation using a tape to peel off the atomic layers from the bulk WSe₂. However, no standardized mechanical exfoliation method reliably produces consistent, large-sized 2D flakes, limiting the scalability of energy-harvesting devices. In this work, WSe₂ 2D flakes were exfoliated using different tapes and peeling angles on SiO₂ substrates of varying cleanliness levels. The optical microscope analysis revealed that polyimide tape, when peeling at 90 degrees, produced the 2D flakes as big as 100 µm. Additionally, experiments with both pre-cleaned (by acetone and isopropyl alcohol) and uncleaned substrates showed that exfoliating on a clean substrate tends to produce flake sizes approximately twice as large as those obtained on an uncleaned substrate. This work highlights the effectiveness and low cost of this method and demonstrates its potential to produce scalable WSe₂ flakes for future industrial energy-harvesting applications.