Out-of-Plane Piezoelectricity and Ferroelectricity in Layered α-In 2 Se 3 Nanoflakes

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…

• EA
  Engineering and Physical Sciences Research Council

  Award: EP/N016718/1
• DO
  Division of Emerging Frontiers in Research and Innovation

  Award: EFMA-1542747