Large enhancement of thermoelectric performance in MoS2/ h-BN heterostructure due to vacancy-induced band hybridization

Jing Wu; Yanpeng Liu; Yi Liu; Yongqing Cai; Yunshan Zhao; Hong Kuan Ng; Kenji Watanabe; Takashi Taniguchi; Gang Zhang; Cheng-Wei Qiu; Dongzhi Chi; A H Castro Neto; John T L Thong; Kian Ping Loh; Kedar Hippalgaonkar

doi:10.1073/pnas.2007495117

Large enhancement of thermoelectric performance in MoS₂/ h-BN heterostructure due to vacancy-induced band hybridization

Proc Natl Acad Sci U S A. 2020 Jun 23;117(25):13929-13936. doi: 10.1073/pnas.2007495117. Epub 2020 Jun 10.

Authors

Jing Wu^{1

2}, Yanpeng Liu^{2

3

4}, Yi Liu^{2

5}, Yongqing Cai⁶, Yunshan Zhao^{2

5

7}, Hong Kuan Ng^{1

8}, Kenji Watanabe⁹, Takashi Taniguchi⁹, Gang Zhang¹⁰, Cheng-Wei Qiu^{2

5

11}, Dongzhi Chi¹, A H Castro Neto^{2

8}, John T L Thong^{12

5}, Kian Ping Loh^{12

3

10}, Kedar Hippalgaonkar^{13

2

14}

Affiliations

¹ Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 138634, Singapore.
² Centre for Advanced 2D Materials, National University of Singapore, 117546, Singapore.
³ Department of Chemistry, National University of Singapore, 117542, Singapore.
⁴ Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China.
⁵ Department of Electrical and Computer Engineering, National University of Singapore, 117583, Singapore.
⁶ Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macau, China.
⁷ School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China.
⁸ Department of Physics, National University of Singapore, 117542, Singapore.
⁹ Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
¹⁰ Institute of High Performance Computing, Agency for Science, Technology and Research, 138632, Singapore.
¹¹ Shenzhen University-National University of Singapore Collaborative Innovation Center for Optoelectronic Science and Technology, Shenzhen University, Shenzhen, 518060, China.
¹² Centre for Advanced 2D Materials, National University of Singapore, 117546, Singapore; john_thong@nus.edu.sg chmlohkp@nus.edu.sg kedar@ntu.edu.sg.
¹³ Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 138634, Singapore; john_thong@nus.edu.sg chmlohkp@nus.edu.sg kedar@ntu.edu.sg.
¹⁴ Department of Materials Science and Engineering, Nanyang Technological University, 639798, Singapore.

Abstract

Local impurity states arising from atomic vacancies in two-dimensional (2D) nanosheets are predicted to have a profound effect on charge transport due to resonant scattering and can be used to manipulate thermoelectric properties. However, the effects of these impurities are often masked by external fluctuations and turbostratic interfaces; therefore, it is challenging to probe the correlation between vacancy impurities and thermoelectric parameters experimentally. In this work, we demonstrate that n-type molybdenum disulfide (MoS₂) supported on hexagonal boron nitride (h-BN) substrate reveals a large anomalous positive Seebeck coefficient with strong band hybridization. The presence of vacancies on MoS₂ with a large conduction subband splitting of 50.0 ± 5.0 meV may contribute to Kondo insulator-like properties. Furthermore, by tuning the chemical potential, the thermoelectric power factor can be enhanced by up to two orders of magnitude to 50 mW m^-1 K^-2 Our work shows that defect engineering in 2D materials provides an effective strategy for controlling band structure and tuning thermoelectric transport.

Keywords: 2D materials; Kondo; Seebeck; phonon drag; thermoelectric.