Published in Nano Letters 18, 1849 (2018).
Quantum-Confined Electronic States arising from Moiré Pattern of MoS2-WSe2 Hetero-bilayers
Yi Pan,1,2 Stefan Fölsch,1 Yifan Nie,3 Dacen Waters,4 Yu-Chuan Lin,5 Bhakti Jariwala,5 Kehao Zhang,5 Kyeongjae Cho,3 Joshua A. Robinson,5 and Randall M. Feenstra4
1Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
2Center for Spintronics and Quantum Systems, State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China
3Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, TX 75080
4Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213
5Dept. Materials Science and Engineering, and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, PA, 16802 U.S.A
Abstract
A two-dimensional (2D) hetero-bilayer system consisting of MoS2 on WSe2, 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 MoS2 and WSe2. 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.
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