Irradiation-induced shrinkage and expansion mechanisms of SiO2 circle membrane nanopores

Electron beam-assisted healing of nanopores in magnesium alloys

Nanopore-based sensing has emerged as a promising candidate for affordable and powerful DNA sequencing technologies. Herein, we demonstrate that nanopores can be successfully fabricated in Mg alloys via focused electron beam (e-beam) technology. Employing in situ high-resolution transmission electron microscopy techniques, we obtained unambiguous evidence that layer-by-layer growth of atomic planes at the nanopore periphery occurs when the e-beam is spread out, leading to the shrinkage and eventual disappearance of nanopores. The proposed healing process was attributed to the e-beam-induced anisotropic diffusion of Mg atoms in the vicinity of nanopore edges. A plausible diffusion mechanism that describes the observed phenomena is discussed. Our results constitute the first experimental investigation of nanopores in Mg alloys. Direct evidence of the healing process has advanced our fundamental understanding of surface science, which is of great practical importance for many technological applications, including thin film deposition and surface nanopatterning.

Resizing metal-coated nanopores using a scanning electron microscope

Electron beam-induced shrinkage provides a convenient way of resizing solid-state nanopores in Si(3) N(4) membranes. Here, a scanning electron microscope (SEM) has been used to resize a range of different focussed ion beam-milled nanopores in Al-coated Si(3) N(4) membranes. Energy-dispersive X-ray spectra and SEM images acquired during resizing highlight that a time-variant carbon deposition process is the dominant mechanism of pore shrinkage, although granular structures on the membrane surface in the vicinity of the pores suggest that competing processes may occur. Shrinkage is observed on the Al side of the pore as well as on the Si(3) N(4) side, while the shrinkage rate is observed to be dependent on a variety of factors.

Controlled deformation of Si3N4 nanopores using focused electron beam in a transmission electron microscope

The controllable deformation of nanopores was realized by moving a convergent electron beam in a high-resolution transmission electron microscope. Nanostructures with the desired geometries were successfully fabricated from the original nanopores in 100 nm-thick and 260 nm-thick Si(3)N(4) membranes. The formation dynamics is a competition process between the knock-on effect of the high-energy electron beam and surface tension driven shrinkage. This approach can be used to finely tune critical dimensions and deform nanopores to particular desired geometries with single-nanometer precision, which offers substantial opportunities in flexibly fabricating nanostructures for various applications such as nanoelectronics and nanofluidics.