Correlation between aperture diameter and deposited iron catalyst. (a) SIM image of the stencil mask fabricated with 1,152 nanoapertures. (b) Tapping-mode AFM image of the iron catalyst deposited onto the substrate through the stencil mask. (c, d) Enlarged SIM and AFM images of the apertures and patterned iron catalyst shown in (a) and (b), respectively. Diameter of the apertures was 60 to 240 nm, and horizontal spacing between apertures was 260 nm. (e, f) Cross-sectional height profiles for iron catalyst deposited along lines indicated by A-A' and B-B' in (d). Height of the deposited catalyst increases with increasing diameter of aperture, and thickness of the iron catalyst deposited through 177-nm aperture is 1.6 to 1.7 nm.