Janus monolayers of transition metal dichalcogenides

Ang-Yu Lu, Hanyu Zhu, Jun Xiao, Chih-Piao Chuu, Yimo Han, Ming-Hui Chiu, Chia-Chin Cheng, Chih-Wen Yang, Kung-Hwa Wei, Yiming Yang, Yuan Wang, Dimosthenis Sokaras, Dennis Nordlund, Peidong Yang, David A. Muller, Mei-Yin Chou, Xiang Zhang, Lain-Jong Li

Research output: Contribution to journalArticlepeer-review

486 Scopus citations

Abstract

Structural symmetry-breaking plays a crucial role in determining the electronic band structures of two-dimensional materials. Tremendous efforts have been devoted to breaking the in-plane symmetry of graphene with electric fields on AB-stacked bilayers or stacked van der Waals heterostructures. In contrast, transition metal dichalcogenide monolayers are semiconductors with intrinsic in-plane asymmetry, leading to direct electronic bandgaps, distinctive optical properties and great potential in optoelectronics. Apart from their in-plane inversion asymmetry, an additional degree of freedom allowing spin manipulation can be induced by breaking the out-of-plane mirror symmetry with external electric fields or, as theoretically proposed, with an asymmetric out-of-plane structural configuration. Here, we report a synthetic strategy to grow Janus monolayers of transition metal dichalcogenides breaking the out-of-plane structural symmetry. In particular, based on a MoS2 monolayer, we fully replace the top-layer S with Se atoms. We confirm the Janus structure of MoSSe directly by means of scanning transmission electron microscopy and energy-dependent X-ray photoelectron spectroscopy, and prove the existence of vertical dipoles by second harmonic generation and piezoresponse force microscopy measurements.
Original languageEnglish (US)
Pages (from-to)744-749
Number of pages6
JournalNature Nanotechnology
Volume12
Issue number8
DOIs
StatePublished - May 15 2017

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