The ability to sieve ions through nanopores with high throughput has significant importance
in seawater desalination and other separation applications. In this study, a plasma etching
process has been demonstrated to be an efficient way to produce high-density nanopores
on graphene membranes with tunable size in the sub-nanometer range. Besides the pore
size, the nanopore density is also controllable through adjusting the exposure time of the
sample to argon or oxygen plasma. The plasma-treated graphene membranes can …

1. Experimental Methods a. Si3N4 Substrate Fabrication Protocol The process of fabrication
silicon nitride (Si3N4) substrate is shown in Figure S1 (a). In the first step, a freestanding
with100 nm thick Si3N4 membrane was deposited on both sides of the< 100> silicon
substrate by low-pressure chemical vapor deposition (LPCVD). Then, optical lithography
and reactive ion etching (RIE) methods were used to etch a 720 μm× 720 μm square
window at the center of the Si3N4 membrane on one side of the silicon wafer. In the third …