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

We present an overexposed PMMA (poly(methyl methacrylate)) technique to realize suspended 2D van der Waals (vdW) MoS 2 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 Al 2 O 3 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 Al 2 O 3 film, which contacts both the top and bottom surfaces of the MoS 2 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.