A Simple Overexposed PMMA Strategy for High-Drain-Current Suspended 2D MoS2 Devices

초록

We present an overexposed PMMA (poly(methyl methacrylate)) technique to realize suspended 2D van der Waals (vdW) MoS2 devices exhibiting higher drain current levels than their on-substrate counterparts. We detail the dose testing and corresponding fabrication process for these suspended devices. Notably, regardless of solvent type or initial spin-coated PMMA thickness, the thickness of overexposed PMMA structures is reduced to approximately 60% of the original value. By applying Al2O3 passivation via atomic layer deposition (ALD), the drain current of the suspended devices increases by 3 orders of magnitude, whereas the on-substrate devices show only a one-order-of-magnitude enhancement. Numerical simulations suggest that fixed charges in the Al2O3 film, which contacts both the top and bottom surfaces of the MoS2 channel, are primarily responsible for the increased drain current in the suspended configuration. We believe these findings offer a practical strategy for fabricating and characterizing 2D vdW materials in a suspended geometry.

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