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Nano Lett. 2017 Sep 13;17(9):5508-5513. doi: 10.1021/acs.nanolett.7b02198. Epub 2017 Aug 30.

Out-of-Plane Piezoelectricity and Ferroelectricity in Layered α-In2Se3 Nanoflakes.

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Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, China.
Department of Physics, University of Texas at Austin , Austin, Texas 78712, United States.
Physical Sciences and Engineering Division, King Abdullah University of Science and Technology , Thuwal 23955-6900, Saudi Arabia.
Department of Physics, Durham University , Durham DH1 3LE, United Kingdom.


Piezoelectric and ferroelectric properties in the two-dimensional (2D) limit are highly desired for nanoelectronic, electromechanical, and optoelectronic applications. Here we report the first experimental evidence of out-of-plane piezoelectricity and ferroelectricity in van der Waals layered α-In2Se3 nanoflakes. The noncentrosymmetric R3m symmetry of the α-In2Se3 samples is confirmed by scanning transmission electron microscopy, second-harmonic generation, and Raman spectroscopy measurements. Domains with opposite polarizations are visualized by piezo-response force microscopy. Single-point poling experiments suggest that the polarization is potentially switchable for α-In2Se3 nanoflakes with thicknesses down to ∼10 nm. The piezotronic effect is demonstrated in two-terminal devices, where the Schottky barrier can be modulated by the strain-induced piezopotential. Our work on polar α-In2Se3, one of the model 2D piezoelectrics and ferroelectrics with simple crystal structures, shows its great potential in electronic and photonic applications.


2D materials; In2Se3; ferroelectric; piezoelectric; polarization

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