@article{1d45a171ee3f41aeb169a3365dc67456,
title = "Ferroelectricity in untwisted heterobilayers of transition metal dichalcogenides",
abstract = "Two-dimensional materials with out-of-plane (OOP) ferroelectric and piezoelectric properties are highly desirable for the realization of ultrathin ferro- and piezoelectronic devices. We demonstrate unexpected OOP ferroelectricity and piezoelectricity in untwisted, commensurate, and epitaxial MoS2/WS2 heterobilayers synthesized by scalable one-step chemical vapor deposition. We show d33 piezoelectric constants of 1.95 to 2.09 picometers per volt that are larger than the natural OOP piezoelectric constant of monolayer In2Se3 by a factor of ~6. We demonstrate the modulation of tunneling current by about three orders of magnitude in ferroelectric tunnel junction devices by changing the polarization state of MoS2/WS2 heterobilayers. Our results are consistent with density functional theory, which shows that both symmetry breaking and interlayer sliding give rise to the unexpected properties without the need for invoking twist angles or moir{\'e} domains.",
author = "Lukas Rog{\'e}e and Lvjin Wang and Yi Zhang and Songhua Cai and Peng Wang and Manish Chhowalla and Wei Ji and Lau, {Shu Ping}",
note = "Funding Information: Supported by Hong Kong Polytechnic University (grant 1-ZVGH), the Research Grants Council of Hong Kong (15306321, C5029-18E, AoE/P-701/20), the National Key R&D Program of China (grant 2018YFE0202700), the National Natural Science Foundation of China (grants 11622437, 11804247, 61674171, and 11974422), the Fundamental Research Funds for the Central Universities of China and the Research Funds of Renmin University of China (grant 22XNKJ30), and the Strategic Priority Research Program of Chinese Academy of Sciences (grant XDB30000000). This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement GA 101019828-2D-LOTTO]), Leverhulme Trust (RPG-2019-227), EPSRC (EP/T026200/1, EP/T001038/1), and Royal Society Wolfson Merit Award (WRM\FT\180009). Publisher Copyright: {\textcopyright} 2022 American Association for the Advancement of Science. All rights reserved.",
year = "2022",
month = may,
day = "26",
doi = "10.1126/science.abm5734",
language = "English",
volume = "376",
journal = "Science",
issn = "0036-8075",
publisher = "American Association for the Advancement of Science",
number = "6596",
}