Direct Fabrication of Sub-10 nm Nanopores in WO₃ Nanosheets Using Single Swift Heavy Ions

Extendingthe fabrication methodology of solid-state nanoporesin a wide range of materials is significant in the fields of singlemolecule detection, nanofluidic devices, and nanofiltration membranes.Here, we demonstrate a new method to directly fabricate size- anddensity-controllable sub-10 nm nanopores in WO3 nanosheetsusing single swift heavy ions (SHIs) without any chemical etchingprocess. By selecting ions of different electronic energy losses (S-e), nanopores with sizes from 1.8 to 7.4 nm can be createdin WO3 nanosheets. The creation efficiency of nanoporesachieves similar to 100% for S-e > 20 keV/nm, and thereexistsa critical thickness below which nanopores can be created. Combinedwith molecular dynamics simulations, we propose that the viscosityand surface tension of the transient molten phase caused by SHIs arethe key factors for the formation of nanopores. This method pavesa way to fabricate solid-state nanopores in materials with a low viscosityand surface tension.