Substrate, environment, and lattice imperfections have a strong impact on the local electronic structure and the optical properties of atomically thin transition metal dichalcogenides. We find by a comparative study of MoS2 on SiO2 and hexagonal boron nitride (hBN) using scanning tunneling spectroscopy (STS) measurements that the apparent bandgap of MoS2 on SiO2 is significantly reduced compared to MoS2 on hBN. The bandgap energies as well as the exciton binding energies determined from all-optical measurements are very similar for MoS2 on SiO2 and hBN. This discrepancy is found to be caused by a substantial amount of band tail states near the conduction band edge of MoS2 supported by SiO2. The presence of those states impacts the local density of states in STS measurements and can be linked to a broad red-shifted photoluminescence peak and a higher charge carrier density that are all strongly diminished or even absent using high quality hBN substrates. By taking into account the substrate effects, we obtain a quasiparticle gap that is in excellent agreement with optical absorbance spectra and we deduce an exciton binding energy of about on and on hBN.
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23 December 2019
Research Article|
December 30 2019
Impact of substrate induced band tail states on the electronic and optical properties of MoS2
J. Klein;
J. Klein
a)
1
Walter Schottky Institut and Physik Department, Technische Universität München
, 85748 Garching, Germany
2
Nanosystems Initiative Munich (NIM)
, 80799 Munich, Germany
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A. Kerelsky;
A. Kerelsky
3
Department of Physics, Columbia University
, New York, New York 10027, USA
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M. Lorke;
M. Lorke
4
Institut für Theoretische Physik, Universität Bremen
, 28334 Bremen, Germany
5
Bremen Center for Computational Materials Science, University of Bremen
, 28359 Bremen, Germany
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M. Florian;
M. Florian
4
Institut für Theoretische Physik, Universität Bremen
, 28334 Bremen, Germany
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F. Sigger;
F. Sigger
1
Walter Schottky Institut and Physik Department, Technische Universität München
, 85748 Garching, Germany
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J. Kiemle;
J. Kiemle
1
Walter Schottky Institut and Physik Department, Technische Universität München
, 85748 Garching, Germany
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M. C. Reuter;
M. C. Reuter
6
IBM T. J. Watson Research Center
, Yorktown Heights, New York 10598, USA
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T. Taniguchi;
T. Taniguchi
7
National Institute for Materials Science
, Tsukuba, Ibaraki 305-0044, Japan
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K. Watanabe
;
K. Watanabe
7
National Institute for Materials Science
, Tsukuba, Ibaraki 305-0044, Japan
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J. J. Finley
;
J. J. Finley
1
Walter Schottky Institut and Physik Department, Technische Universität München
, 85748 Garching, Germany
2
Nanosystems Initiative Munich (NIM)
, 80799 Munich, Germany
8
Munich Center for Quantum Science and Technology (MCQST)
, 80799 Munich, Germany
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A. N. Pasupathy;
A. N. Pasupathy
3
Department of Physics, Columbia University
, New York, New York 10027, USA
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A. W. Holleitner;
A. W. Holleitner
1
Walter Schottky Institut and Physik Department, Technische Universität München
, 85748 Garching, Germany
2
Nanosystems Initiative Munich (NIM)
, 80799 Munich, Germany
8
Munich Center for Quantum Science and Technology (MCQST)
, 80799 Munich, Germany
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F. M. Ross
;
F. M. Ross
b)
6
IBM T. J. Watson Research Center
, Yorktown Heights, New York 10598, USA
9
Department of Materials Science and Engineering, Massachusetts Institute of Technology
, Cambridge, Massachusetts 02139, USA
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U. Wurstbauer
U. Wurstbauer
c)
1
Walter Schottky Institut and Physik Department, Technische Universität München
, 85748 Garching, Germany
2
Nanosystems Initiative Munich (NIM)
, 80799 Munich, Germany
10
Institute of Physics, University of Münster
, 48149 Münster, Germany
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a)
Electronic mail: [email protected]
b)
Electronic mail: [email protected]
c)
Electronic mail: [email protected]
Appl. Phys. Lett. 115, 261603 (2019)
Article history
Received:
October 14 2019
Accepted:
December 05 2019
Citation
J. Klein, A. Kerelsky, M. Lorke, M. Florian, F. Sigger, J. Kiemle, M. C. Reuter, T. Taniguchi, K. Watanabe, J. J. Finley, A. N. Pasupathy, A. W. Holleitner, F. M. Ross, U. Wurstbauer; Impact of substrate induced band tail states on the electronic and optical properties of MoS2. Appl. Phys. Lett. 23 December 2019; 115 (26): 261603. https://doi.org/10.1063/1.5131270
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