Fig. 1: Etching hexagonal nanostructures in TMD materials.
From: Transition metal dichalcogenide metamaterials with atomic precision
a Schematic of the fabrication method: (i) transfer of a mechanically exfoliated TMD flake on a SiO2/Si substrate, (ii) nanopatterning of the transferred flake using standard top-down lithography, and (iii) anisotropic wet etching of the pre-patterned flake by water solution of hydrogen peroxide and ammonia. b Time-resolved anisotropic wet etching for a single hole in a WS2 multilayer flake. Leftmost and rightmost panels show SEM images of the hole after 0 min and 16 min of etching, respectively. c 70° tilted SEM image of anisotropically etched WS2 flake, revealing hexagonal holes and their orientation. d TEM image of an etched WS2 hexagonal array. The inset shows a selected area electron diffraction pattern from the imaged area, revealing a single crystalline WS2 diffraction pattern along a [0001] zone axis with an orientation that confirms the etched surfaces are aligned with the zigzag-terminated direction. The red and green circles identify the 1100 and 1120 families of diffraction spots, respectively. e HRTEM image of an etched surface, revealing its nearly atomically sharp zigzag nature. The inset shows a scanning TEM (STEM) EELS spectrum acquired with the electron probe positioned directly at the etched zigzag surface, revealing the presence of strong A-, B-, and C-exciton signals.
