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We present a versatile method to fabricate conical nanopores of different materials and shapes on silicon/silicon nitride chips for various nanoscale applications. We drilled silicon nitride membranes coated with photoresist with Focused Ion Beam (FIB) calibrated to the desired shape, followed by atomic layer deposition of a dielectric oxide and subsequent photoresist removal and annealing. We obtained conical nanopores made of SiO2 and Al2O3 on a silicon nitride membrane. We characterized the samples electrically, with Scanning Electron Microscopy (SEM), cross sections and Energy-Dispersive X-ray spectroscopy (EDX). We studied concave, straight, and convex nanopore shapes and measured their ionic current rectification effects, which vary with the nanopore geometry. We supported our experimental findings with numerical simulations based on the Poisson-Nernst-Planck model. With the addition of a metallic layer, we conducted enhanced Raman spectroscopy experiments to confirm the capacity of our structures to perform as tailored plasmonic antennas. Our results confirm the robustness and tunability of this fabrication method to produce conical nanopores of dielectric oxides for a wide range of applications and the potential of controlling the nanopore geometry.
Lanzavecchia et al. (Mon,) studied this question.