Reliable Piezoelectricity in Bilayer WSe2 for Piezoelectric Nanogenerators. Issue 29 (6th June 2017)

• Record Type: Journal Article
• Authors: Lee, Ju‐Hyuck; Park, Jae Young; Cho, Eun Bi; Kim, Tae Yun; Han, Sang A.; Kim, Tae‐Ho; Liu, Yanan; Kim, Sung Kyun; Roh, Chang Jae; Yoon, Hong‐Joon; Ryu, Hanjun; Seung, Wanchul; Lee, Jong Seok; Lee, Jaichan; Kim, Sang‐Woo
• Is Part Of: Advanced materials. Volume 29:Issue 29(2017)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-06-06
• Subjects: 2D materials -- atomic stacking -- nanogenerators -- piezoelectricity -- tungsten diselenide; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.201606667
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract : Recently, piezoelectricity has been observed in 2D atomically thin materials, such as hexagonal‐boron nitride, graphene, and transition metal dichalcogenides (TMDs). Specifically, exfoliated monolayer MoS2 exhibits a high piezoelectricity that is comparable to that of traditional piezoelectric materials. However, monolayer TMD materials are not regarded as suitable for actual piezoelectric devices due to their insufficient mechanical durability for sustained operation while Bernal‐stacked bilayer TMD materials lose noncentrosymmetry and consequently piezoelectricity. Here, it is shown that WSe2 bilayers fabricated via turbostratic stacking have reliable piezoelectric properties that cannot be obtained from a mechanically exfoliated WSe2 bilayer with Bernal stacking. Turbostratic stacking refers to the transfer of each chemical vapor deposition (CVD)‐grown WSe2 monolayer to allow for an increase in degrees of freedom in the bilayer symmetry, leading to noncentrosymmetry in the bilayers. In contrast, CVD‐grown WSe2 bilayers exhibit very weak piezoelectricity because of the energetics and crystallographic orientation. The flexible piezoelectric WSe2 bilayers exhibit a prominent mechanical durability of up to 0.95% of strain as well as reliable energy harvesting performance, which is adequate to drive a small liquid crystal display without external energy sources, in contrast to monolayer WSe2 for which the device performance becomes degraded above a strain of 0.63%. Abstract : WSe2 bilayers with turbostratic stacking have reliable piezoelectric properties that cannot be obtained from a WSe2 monolayer. The flexible piezoelectric WSe2 bilayers exhibit a prominent mechanical durability of up to 0.95% of strain as well as reliable energy harvesting performance, which is adequate to drive a small liquid crystal display without external energy sources.