Piezoelectricity of single-atomic-layer MoS2 for energy conversion and piezotronics

• Published in: Nature (London) 2014-10, Vol.514 (7523), p.470-474
• Main Authors: Wu, Wenzhuo, Wang, Lei, Li, Yilei, Zhang, Fan, Lin, Long, Niu, Simiao, Chenet, Daniel, Zhang, Xian, Hao, Yufeng, Heinz, Tony F., Hone, James, Wang, Zhong Lin
• Format: Article
• Language: English
• Subjects: 639/925/918/1052; 639/925/927/1007; Humanities and Social Sciences; letter; multidisciplinary; Science
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature13792

The two-dimensional semiconducting material molybdenum disulphide shows strong piezoelectricity in its single-layered form, suggesting possible applications in nanoscale electromechanical devices for sensing and energy harvesting. Piezoelectricity in monolayer MoS 2 Two-dimensional semiconducting materials are the focus of much research effort thanks to their unusual and potentially useful physical properties. Wenzhou Wu and colleagues now confirm theoretical expectations that one such material — molybdenum disulphide — exhibits strong piezoelectricity in its single-layered form. Such a coupling of mechanical and electrical properties suggests possible applications in nanoscale electromechanical devices for sensing and energy harvesting. The piezoelectric characteristics of nanowires, thin films and bulk crystals have been closely studied for potential applications in sensors, transducers, energy conversion and electronics 1 , 2 , 3 . With their high crystallinity and ability to withstand enormous strain 4 , 5 , 6 , two-dimensional materials are of great interest as high-performance piezoelectric materials. Monolayer MoS 2 is predicted to be strongly piezoelectric, an effect that disappears in the bulk owing to the opposite orientations of adjacent atomic layers 7 , 8 . Here we report the first experimental study of the piezoelectric properties of two-dimensional MoS 2 and show that cyclic stretching and releasing of thin MoS 2 flakes with an odd number of atomic layers produces oscillating piezoelectric voltage and current outputs, whereas no output is observed for flakes with an even number of layers. A single monolayer flake strained by 0.53% generates a peak output of 15 mV and 20 pA, corresponding to a power density of 2 mW m −2 and a 5.08% mechanical-to-electrical energy conversion efficiency. In agreement with theoretical predictions, the output increases with decreasing thickness and reverses sign when the strain direction is rotated by 90°. Transport measurements show a strong piezotronic effect in single-layer MoS 2 , but not in bilayer and bulk MoS 2 . The coupling between piezoelectricity and semiconducting properties in two-dimensional nanomaterials may enable the development of applications in powering nanodevices, adaptive bioprobes and tunable/stretchable electronics/optoelectronics.