Fig. 1: The electric field leakage effect in Al₂O₃-coated polymer nanopores.

a Set-up to measure resistive pulses from the translocation of individual DNA molecules through single bullet-shaped polymer nanopore coated with a thin Al₂O₃ layer. b Electrostatic modeling of an Al₂O₃-coated bullet-like nanopore (tip diameter: 8 nm, half cone angle: 8°) simulated with an applied voltage of 500 mV. Electric field direction and intensity were evaluated numerically on the tip side of the Al₂O₃-coated polymer nanopore. The electric field is significantly enhanced and develops a normal field leakage near the sharp pore edge. Scale bar = 3 nm. c Validation of Eq. (1) through the use of finite-element-method simulations for normal field leakage in the dielectric film. Different permittivities (black squares, ε_film: 5~17) and film thicknesses (red circles, l : 1~27 nm) were sampled. Inset shows the schematics of a high-permittivity dielectric film on an insulating polymer nanopore orifice and the Gauss volume used to estimate the leakage field around the pore. d Left: Surface plots of the strength of normal leakage field (E_leak) showing the normal leakage field at the pore edge is a strong function of Al₂O₃ film thickness (nanopore diameter, 8 nm). Right: Axial dependence of the normal leakage field as a function of distance from the pore mouth r for three Al₂O₃ film thicknesses.