  The ability to extract materials just a few atoms thick has led to discovery
of graphene, monolayer transition metal dichalcogenides (TMDs), and other
important two-dimensional materials. The next step in promoting understanding
and utility of the flatland physics beyond the state-of-the-art is to study
one-dimensional edges of such two-dimensional materials as well as to control
the edge-plane ratio. Edges typically exhibit properties that are unique and
distinctly different from those of planes and bulk. Thus, controlling them
allows to design principally new materials with synthetic edge-plane-bulk
characteristics, that is, TMD metamaterials. However, the enabling technology
to study such metamaterials experimentally in a precise and systematic way has
not yet been developed. Here we report a facile and controllable anisotropic
wet etching method that allows scalable fabrication of TMD metamaterials with
atomic precision. We show that TMDs can be etched along certain
crystallographic axes, such that the obtained edges are atomically sharp and
exclusively zigzag-terminated. This results in hexagonal nanostructures of
predefined order and complexity, including few nanometer thin nanoribbons and
nanojunctions. The method thus enables future studies of a broad range of TMD
metamaterials with tailored functionality through atomically precise control of
the structure.
