Atomic-scale symmetry breaking for out-of-plane piezoelectricity in two-dimensional transition metal dichalcogenides

• Published in: Nano energy 2019-04, Vol.58, p.57-62
• Main Authors: Kang, Seunghun, Kim, Sera, Jeon, Sera, Jang, Woo-Sung, Seol, Daehee, Kim, Young-Min, Lee, Jaekwang, Yang, Heejun, Kim, Yunseok
• Format: Article
• Language: English
• Subjects: Flexoelectricity; Out-of-plane piezoelectricity; Piezoresponse force microscopy; Te vacancy; Transition metal dichalcogenides
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2019.01.025

It is known that only in-plane piezoelectricity exists in pristine two dimensional (2D) transition metal dichalcogenides (TMDs). In this study, we demonstrate the creation of strong out-of-plane piezoelectricity in semiconducting 2H-MoTe2 flakes by an artificial atomic-scale symmetry breaking. The atomic-scale symmetry breaking associated with flexoelectricity was realized through Te vacancy formation by a simple thermal annealing of the 2D TMDs. The strong out-of-plane piezoelectricity was experimentally measured and confirmed by theoretical calculations. This strategy of atomic-scale symmetry modulation for out-of-plane piezoelectricity can be easily applied to a broader class of 2D TMD materials that have not been used for applications with out-of-plane piezoelectricity. Accordingly, it can stimulate the expansion of practical energy device applications with 2D TMD materials. [Display omitted] •Achievement of strong out-of-plane piezoelectricity.•Atomic-scale symmetry breaking via Te vacancy formation.•Simple strategy for inducing out-of-plane piezoelectricity by thermal annealing.