Extended Data Fig. 1: Fabrication process flow.
From: Beyond steric selectivity of ions using ångström-scale capillaries
The sequence of fabrication steps is indicated by the arrows. (a) Freestanding silicon nitride (SiNx) membrane (100 × 100 µm2) was prepared by wet etching. (b) Rectangular aperture (typically, 3 × 26 µm2) was made in the membrane using photolithography and dry etching. (c) Bottom 2D crystal was placed on top of the aperture. (d) Strips of bilayer graphene were transferred onto the bottom crystal. Then the two-layer assembly was dry etched from the back with the SiNx aperture serving as a protective mask. (e) Another 2D crystal (top layer) was placed on top to cover the entire etched microhole. (f) A gold stripe was deposited on top of the trilayer assembly. (g) This stripe was used as a mask for subsequent dry etching. The inset shows schematically a cross-section of the resulting Å-channels.
