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2D Electrets of Ultrathin MoO 2 with Apparent Piezoelectricity
Author(s) -
Apte Amey,
Mozaffari Kosar,
Samghabadi Farnaz Safi,
Hachtel Jordan A.,
Chang Long,
Susarla Sandhya,
Idrobo Juan Carlos,
Moore David C.,
Glavin Nicholas R.,
Litvinov Dmitri,
Sharma Pradeep,
Puthirath Anand B.,
Ajayan Pulickel M.
Publication year - 2020
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.202000006
Subject(s) - piezoelectricity , electret , materials science , flexoelectricity , energy harvesting , nanotechnology , optoelectronics , graphene , composite material , energy (signal processing) , statistics , mathematics
Since graphene, a variety of 2D materials have been fabricated in a quest for a tantalizing combination of properties and desired physiochemical behavior. 2D materials that are piezoelectric, i.e., that allow for a facile conversion of electrical energy into mechanical and vice versa, offer applications for sensors, actuators, energy harvesting, stretchable and flexible electronics, and energy storage, among others. Unfortunately, materials must satisfy stringent symmetry requirements to be classified as piezoelectric. Here, 2D ultrathin single‐crystal molybdenum oxide (MoO 2 ) flakes that exhibit unexpected piezoelectric‐like response are fabricated, as MoO 2 is centrosymmetric and should not exhibit intrinsic piezoelectricity. However, it is demonstrated that the apparent piezoelectricity in 2D MoO 2 emerges from an electret‐like behavior induced by the trapping and stabilization of charges around defects in the material. Arguably, the material represents the first 2D electret material and suggests a route to artificially engineer piezoelectricity in 2D crystals. Specifically, it is found that the maximum out‐of‐plane piezoresponse is 0.56 pm V −1 , which is as strong as that observed in conventional 2D piezoelectric materials. The charges are found to be highly stable at room temperature with a trapping energy barrier of ≈2 eV.