Precise Shrinkage of Silicon Nitride Nanopores Via Externally Sourced Hydrocarbons

Solid-state nanopores (SSNPs) are progressively gaining importance in biomolecular sensing and ionic circuit applications. Unlocking their full potential, however, requires the development of fabrication techniques that enable precise control over their sizes and shapes. Electron-beam (EB) shrinking provides precise, real-time feedback and is ideally suited to address these requirements. However, it necessitates an initial pore diameter smaller than the membrane thickness for effective shrinking without material addition. Typical focused ion beam (FIB)-drilled pores in silicon nitride membranes often fail to meet these requirements. Alternative efforts towards mitigating these bottlenecks through deploying hydrocarbon-mediated EB shrinkage face challenges due to uncontrolled carbon contamination or a lack thereof in cleaner transmission electron microscope (TEM) chambers. To address these challenges, here we report an alternative approach of high-precision hydrocarbon-mediated EB shrinking with hydrocarbons sourced externally through controlled surface reactions on exposure to ethanol. This provides several decisive advantages, including the reduction of pore diameters much larger than the membrane thickness and controlled shrinking in cleaner environments without contaminations. These measures accelerate nanopore fabrication, improve its predictability by eliminating the dependence on variable carbon contamination in vacuum chambers, and provide high-resolution live feedback during dimension tuning. As a result, our method supports the large-scale production of nanopores with analyte-specific, tuneable dimensions. This capability is particularly imperative for low-noise biomolecular sequencing applications that leverage electrically-modulated transport and sensing over nanoscales. These features could pave the way for the broader application of SSNPs, addressing long-standing challenges in their fabrication and functionalisation that remained unresolved thus far.