Impurity-Induced Emission in Re-Doped WS2 Monolayers

Leyi Loh; Yifeng Chen; Junyong Wang; Xinmao Yin; Chi Sin Tang; Qi Zhang; Kenji Watanabe; Takashi Taniguchi; Andrew Ts Wee; Michel Bosman; Su Ying Quek; Goki Eda

doi:10.1021/acs.nanolett.1c01439

Impurity-Induced Emission in Re-Doped WS₂ Monolayers

Nano Lett. 2021 Jun 23;21(12):5293-5300. doi: 10.1021/acs.nanolett.1c01439. Epub 2021 Jun 11.

Authors

Leyi Loh^{1

2}, Yifeng Chen^{1

3}, Junyong Wang¹, Xinmao Yin^{1

4

5}, Chi Sin Tang^{1

5

6}, Qi Zhang¹, Kenji Watanabe⁷, Takashi Taniguchi⁸, Andrew Ts Wee^{1

3}, Michel Bosman², Su Ying Quek^{1

2

3}, Goki Eda^{1

3

9}

Affiliations

¹ Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore.
² Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575 Singapore.
³ Centre for Advanced 2D Materials, National University of Singapore, 2 Science Drive 2, 117542, Singapore.
⁴ Shanghai Key Laboratory of High Temperature Superconductors, Physics Department, Shanghai University, Shanghai 200444, China.
⁵ Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, 117603 Singapore.
⁶ Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, 138634 Singapore.
⁷ Research Centre for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
⁸ International Centre for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
⁹ Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543 Singapore.

PMID: 34115939
DOI: 10.1021/acs.nanolett.1c01439

Abstract

Impurity doping is a viable route toward achieving desired subgap optical response in semiconductors. In strongly excitonic two-dimensional (2D) semiconductors such as transition metal dichalcogenides (TMDs), impurities are expected to result in bound-exciton emission. However, doped TMDs often exhibit a broad Stokes-shifted emission without characteristic features, hampering strategic materials engineering. Here we report observation of a well-defined impurity-induced emission in monolayer WS₂ substitutionally doped with rhenium (Re), which is an electron donor. The emission exhibits characteristics of localized states and dominates the spectrum up to 200 K. Gate dependence reveals that neutral impurity centers are responsible for the observed emission. Using GW-Bethe-Salpeter equation (GW-BSE) calculations, we attribute the emission to transitions between spin-split upper Re band and valence band edge.

Keywords: bound excitons; defect emission; substitutional doping; transition metal dichalcogenides; two-dimensional (2D) semiconductors.