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 nano-flakes. The non-centrosymmetric 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 nano-flakes 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.
|Original language||English (US)|
|Number of pages||6|
|State||Published - Aug 30 2017|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The PFM work is supported by the Welch Foundation Grant F-1814. D.W. and Z.C. also acknowledges the support from NSF EFRI under Award # EFMA-1542747. The SHG work (Y. C. and M. C. D.) is supported by Welch Grant F-1038. The sample synthesis and device fabrication work are supported by the National Basic Research Program of China (No. 2014CB932500) and the National Natural Science Foundation of China (No. 21525310).