  Polymorphic structures of transition-metal dichalcogenides (TMDs) host exotic
electronic states, like charge density wave and superconductivity. However, the
number of these structures is limited by crystal symmetries, which poses a
challenge to achieve tailored lattices and properties both theoretically and
experimentally. Here, we report a coloring-triangle (CT) latticed MoTe2
monolayer, termed CT-MoTe2, constructed by controllably introducing uniform and
ordered mirror-twin-boundaries into a pristine monolayer in molecular beam
epitaxy. Low-temperature scanning tunneling microscopy and spectroscopy
(STM/STS) together with theoretical calculations reveal that the monolayer has
an electronic Janus lattice, i.e., an energy-dependent atomic-lattice and a
pseudo-Te sublattice, and shares the identical geometry with the Mo5Te8 layer.
Dirac-like and flat electronic bands inherently existing in the CT lattice are
identified by two broad and two prominent peaks in STS spectra, respectively,
and verified with density-functional-theory calculations. Two types of
intrinsic domain boundaries were observed, in one of which the
electronic-Janus-lattice feature maintains, implying potential applications as
an energy-tunable electron-tunneling barrier in future functional devices.
