Monolayer WS₂ Nanopores for DNA Translocation with Light-Adjustable Sizes

Two-dimensional materials are promising for a range of applications, as well as testbeds for probing the physics of low-dimensional systems. Tungsten disulfide (WS₂) monolayers exhibit a direct band gap and strong photoluminescence (PL) in the visible range, opening possibilities for advanced optoelectronic applications. Here, we report the realization of two-dimensional nanometer-size pores in suspended monolayer WS₂ membranes, allowing for electrical and optical response in ionic current measurements. A focused electron beam was used to fabricate nanopores in WS₂ membranes suspended on silicon-based chips and characterized using PL spectroscopy and aberration-corrected high-resolution scanning transmission electron microscopy. It was observed that the PL intensity of suspended WS₂ monolayers is ∼10-15 times stronger when compared to that of substrate-supported monolayers, and low-dose scanning transmission electron microscope viewing and drilling preserves the PL signal of WS₂ around the pore. We establish that such nanopores allow ionic conductance and DNA translocations. We also demonstrate that under low-power laser illumination in solution, WS₂ nanopores grow slowly in size at an effective rate of ∼0.2-0.4 nm/s, thus allowing for atomically controlled nanopore size using short light pulses.