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Title: Electronic structure, surface doping, and optical response in epitaxial WSe2 thin films

Abstract

© 2016 American Chemical Society. High quality WSe 2 films have been grown on bilayer graphene (BLG) with layer-by-layer control of thickness using molecular beam epitaxy. The combination of angle-resolved photoemission, scanning tunneling microscopy/spectroscopy, and optical absorption measurements reveal the atomic and electronic structures evolution and optical response of WSe 2 /BLG. We observe that a bilayer of WSe 2 is a direct bandgap semiconductor, when integrated in a BLG-based heterostructure, thus shifting the direct-indirect band gap crossover to trilayer WSe 2 . In the monolayer limit, WSe 2 shows a spin-splitting of 475 meV in the valence band at the K point, the largest value observed among all the MX 2 (M = Mo, W; X = S, Se) materials. The exciton binding energy of monolayer-WSe 2 /BLG is found to be 0.21 eV, a value that is orders of magnitude larger than that of conventional three-dimensional semiconductors, yet small as compared to other two-dimensional transition metal dichalcogennides (TMDCs) semiconductors. Finally, our finding regarding the overall modification of the electronic structure by an alkali metal surface electron doping opens a route to further control the electronic properties of TMDCs.

Authors:
 [1];  [2];  [3];  [4];  [3];  [5];  [6];  [3];  [7];  [8];  [9];  [10];  [11];  [12];  [12];  [8];  [13];  [8]
  1. Nanjing Univ., Nanjing (China); SLAC National Accelerator Lab., Menlo Park, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Univ. of California, Berkeley, CA (United States); CIC nanoGUNE, Donostia-San Sebastian (Spain); Ikerbasque, Basque Foundation for Science, Bilbao (Spain)
  3. Univ. of California, Berkeley, CA (United States)
  4. Univ. of California, Berkeley, CA (United States); Rensselaer Polytechnic Inst., Troy, NY (United States)
  5. Univ. of California, Berkeley, CA (United States); Univ. Autonoma de Madrid, Madrid (Spain)
  6. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Pohang Univ. of Science and Technology, Pohang (Korea)
  7. Stanford Univ., Stanford, CA (United States); Chinese Academy of Sciences, Shanghai (China)
  8. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  9. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Stanford Univ., Stanford, CA (United States); Univ. of Oxford, Oxford (United Kingdom)
  10. Pohang Univ. of Science and Technology, Pohang (Korea); Pusan National Univ., Busan (Korea)
  11. Univ. of Oxford, Oxford (United Kingdom)
  12. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  13. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1257732
Alternate Identifier(s):
OSTI ID: 1393040
Report Number(s):
SLAC-PUB-16566
Journal ID: ISSN 1530-6984
Grant/Contract Number:  
AC02-76SF00515; AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 16; Journal Issue: 4; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ARPES; exciton binding energy; MBE; STM/STS; Transition metal dichalcogenides; WSe2

Citation Formats

Zhang, Yi, Ugeda, Miguel M., Jin, Chenhao, Shi, Su -Fei, Bradley, Aaron J., Martin-Recio, Ana, Ryu, Hyejin, Kim, Jonghwan, Tang, Shujie, Kim, Yeongkwan, Zhou, Bo, Hwang, Choongyu, Chen, Yulin, Wang, Feng, Crommie, Michael F., Hussain, Zahid, Shen, Zhi -Xun, and Mo, Sung -Kwan. Electronic structure, surface doping, and optical response in epitaxial WSe2 thin films. United States: N. p., 2016. Web. doi:10.1021/acs.nanolett.6b00059.
Zhang, Yi, Ugeda, Miguel M., Jin, Chenhao, Shi, Su -Fei, Bradley, Aaron J., Martin-Recio, Ana, Ryu, Hyejin, Kim, Jonghwan, Tang, Shujie, Kim, Yeongkwan, Zhou, Bo, Hwang, Choongyu, Chen, Yulin, Wang, Feng, Crommie, Michael F., Hussain, Zahid, Shen, Zhi -Xun, & Mo, Sung -Kwan. Electronic structure, surface doping, and optical response in epitaxial WSe2 thin films. United States. https://doi.org/10.1021/acs.nanolett.6b00059
Zhang, Yi, Ugeda, Miguel M., Jin, Chenhao, Shi, Su -Fei, Bradley, Aaron J., Martin-Recio, Ana, Ryu, Hyejin, Kim, Jonghwan, Tang, Shujie, Kim, Yeongkwan, Zhou, Bo, Hwang, Choongyu, Chen, Yulin, Wang, Feng, Crommie, Michael F., Hussain, Zahid, Shen, Zhi -Xun, and Mo, Sung -Kwan. 2016. "Electronic structure, surface doping, and optical response in epitaxial WSe2 thin films". United States. https://doi.org/10.1021/acs.nanolett.6b00059. https://www.osti.gov/servlets/purl/1257732.
@article{osti_1257732,
title = {Electronic structure, surface doping, and optical response in epitaxial WSe2 thin films},
author = {Zhang, Yi and Ugeda, Miguel M. and Jin, Chenhao and Shi, Su -Fei and Bradley, Aaron J. and Martin-Recio, Ana and Ryu, Hyejin and Kim, Jonghwan and Tang, Shujie and Kim, Yeongkwan and Zhou, Bo and Hwang, Choongyu and Chen, Yulin and Wang, Feng and Crommie, Michael F. and Hussain, Zahid and Shen, Zhi -Xun and Mo, Sung -Kwan},
abstractNote = {© 2016 American Chemical Society. High quality WSe 2 films have been grown on bilayer graphene (BLG) with layer-by-layer control of thickness using molecular beam epitaxy. The combination of angle-resolved photoemission, scanning tunneling microscopy/spectroscopy, and optical absorption measurements reveal the atomic and electronic structures evolution and optical response of WSe 2 /BLG. We observe that a bilayer of WSe 2 is a direct bandgap semiconductor, when integrated in a BLG-based heterostructure, thus shifting the direct-indirect band gap crossover to trilayer WSe 2 . In the monolayer limit, WSe 2 shows a spin-splitting of 475 meV in the valence band at the K point, the largest value observed among all the MX 2 (M = Mo, W; X = S, Se) materials. The exciton binding energy of monolayer-WSe 2 /BLG is found to be 0.21 eV, a value that is orders of magnitude larger than that of conventional three-dimensional semiconductors, yet small as compared to other two-dimensional transition metal dichalcogennides (TMDCs) semiconductors. Finally, our finding regarding the overall modification of the electronic structure by an alkali metal surface electron doping opens a route to further control the electronic properties of TMDCs.},
doi = {10.1021/acs.nanolett.6b00059},
url = {https://www.osti.gov/biblio/1257732}, journal = {Nano Letters},
issn = {1530-6984},
number = 4,
volume = 16,
place = {United States},
year = {Mon Mar 14 00:00:00 EDT 2016},
month = {Mon Mar 14 00:00:00 EDT 2016}
}

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Ultra‐Long Lifetimes of Single Quantum Emitters in Monolayer WSe 2 /hBN Heterostructures
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