Fig. 2: Design and fabrication of self-assembled silicon nanobeam bowtie cavities.
From: Self-assembled photonic cavities with atomic-scale confinement
a, Geometry of the nanobeam bowtie cavity. b, Normalized electric field of the cavity mode, ∣E∣, with a logarithmic colour map. c, Normalized electric field, ∣E∣, of the central bowtie unit cell of the nanobeam cavity, with a linear colour map. d, Electron-beam-lithography mask schematic of the central region of the nanobeam cavity, with black (grey) illustrating exposed (unexposed) areas. The offset, δ, is defined as δ = (gP − gT)/2. e, Tilted (20°) SEM image of the central part of the cavity before the release etch triggers the self-assembly of the two parts initially separated by gf = 50 nm, except at the bowtie where the distance is gb = 52 nm. f, Tilted (20°) SEM of the central part of a nanobeam cavity after self-assembly, with the approximately 2 nm gap indicated in the zoom-in. g, Top-view SEM image of the full device, including the spring suspension. h,i, Top-view high-resolution STEM images of the central unit cell and their bowtie tips for cavities fabricated using δ = 10 nm (h) and δ = 11 nm (i). The scale bars are calibrated using the 0.19 nm interplanar distance of the visible (022) crystalline silicon planes. Scale bars, 200 nm (e,f, top); 20 nm (e,f, bottom); 2 µm (g, top); 1 µm (g, bottom); 100 nm (h,i, left); 2 nm (h,i, right).
