Size control of nanopores formed on SiO2 glass by swift-heavy-ion irradiation and its application to highly sensitive biomolecular detection
Surface SEM images of thermally grown SiO2 glass on Si substrates perforated by irradiation of 137 MeV Au ions with a fluence of ∼5 × 109 cm−2, and subsequent etching using HF vapor resulting from a 20% HF solution. The vertical and horizontal axes represent the temperatures of the substrate and HF solution during the etching, respectively.
Surface SEM images of the perforated sensing plates. The images obtained for plates A–F are shown in (a)–(f), respectively.
Reflection spectra of the perforated plates. The spectra obtained for plates A–D before (open circles), and after (solid circles) the adsorption of streptavidin are shown in (a)–(d), respectively. The solid curve in each figure shows the fitting result to estimate the thickness, t, of the mixture layer composed of the cylindrical nanopores and remaining SiO2 glass.
Schematic drawing of the structure showing assumptions used to estimate the thickness, t, of the mixture layer of the cylindrical nanopores and remaining SiO2 glass.
Dip-angle shift, Δθ d, as a function of the normalized surface area R s. Note that the characters in the figure represent plates A–F shown in Table I.
Schematic drawing of the structure showing assumptions used to calculate the reflection spectra after the streptavidin adsorption.
Correlation between the dip-angle shifts, Δθ d, experimentally and theoretically obtained.
Temperatures of plates that underwent etching to obtain nanopores. Diameter, d n, (average ± one standard deviation) and number density, φ n, of nanopores obtained for each sensing plate are also listed. Furthermore, volume fraction, f b, of nanopores in the mixture layer composed of the nanopores and remaining SiO2 glass, average refractive index, n gb, of the layer, and the layer thickness, t, are also listed for each plate.
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