Control of Shape and Material Composition of Solid-State Nanopores

Solid-state nanopores fabricated by a high-intensity electron beam in ceramic membranes can be fine-tuned on three-dimensional geometry and composition by choice of materials and beam sculpting conditions. For similar beam conditions, 8 nm diameter nanopores fabricated in membranes containing SiO2 show large depletion areas (70 nm in radius) with small sidewall angles (55 degrees), whereas those made in SiN membranes show small depletion areas (40 nm) with larger sidewall angles (75). Three-dimensional electron tomograms of nanopores fabricated in a SiO2/SiN/SiO2 membrane show a biconical shape with symmetric top and bottom and indicate a mixing of SiN and SiO2 layers up to 30 nm from the edge of nanopore, with Si-rich particles throughout the membrane. Electron-energy-loss spectroscopy (EELS) reveals that the oxygen/nitrogen ratio near the pore depends on the beam sculpting conditions.