Nano Letters

Control of shape and material composition of solid-state nanopores

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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 SiO 2 show large depletion areas (70 nm in radius) with small sidewall angles (55°), 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 SiO 2/SiN/SiO 2 membrane show a biconical shape with symmetric top and bottom and indicate a mixing of SiN and SiO 2 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. © 2009 American Chemical Society.