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Quantum-Confined Electronic States Arising from the Moiré Pattern of MoS<sub>2</sub>–WSe<sub>2</sub> Heterobilayers
A two-dimensional
(2D) heterobilayer system consisting of MoS<sub>2</sub> on WSe<sub>2</sub>, deposited on epitaxial graphene, is studied
by scanning tunneling microscopy and spectroscopy at temperatures
of 5 and 80 K. A moiré pattern is observed, arising from lattice
mismatch of 3.7% between the MoS<sub>2</sub> and WSe<sub>2</sub>.
Significant energy shifts are observed in tunneling spectra observed
at the maxima of the moiré corrugation, as compared with spectra
obtained at corrugation minima, consistent with prior work. Furthermore,
at the minima of the moiré corrugation, sharp peaks in the
spectra at energies near the band edges are observed for spectra acquired
at 5 K. The peaks correspond to discrete states that are confined
within the moiré unit cells. Conductance mapping is employed
to reveal the detailed structure of the wave functions of the states.
For measurements at 80 K, the sharp peaks in the spectra are absent,
and conductance maps of the band edges reveal little structure