The researchers explain that much more realistic profiles can be derived by measuring the electrical current throughout the etching process, in particular during the initial stages of perforation. The reconstruction is free of geometric assumptions. It reflects a highly soluble zone close to the ion track axis that extends up to 10 nm and a radiation-hardened zone, which can be up to 100 nm. The constriction is about 1 µm long and has a diameter below 100 nm, which was supported by high-resolution scanning electron microscopy data.

The revised geometry is relevant for nanodevices. The mobility of molecules depends critically on the constriction diameter and the tapering angle of the pore. Thanks to the reconstruction algorithm suggested by the team, these critical parameters can be accurately determined. Furthermore, immobilized charges at the pore wall define the interaction of the solute, its adsorption and the molecules dwell time in the pore.

The technique has far-reaching consequences for applications in nanofluidics, molecular sensors, current rectification and chemical valves.

Full details can be found in the journal Nanotechnology.