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Controlling the Quadruple-well State in CuIn<sub>2</sub>P<sub>2</sub>S<sub>6</sub> via Interfacial PbZr<sub>0.2</sub>Ti<sub>0.8</sub>O<sub>3</sub>

ORAL

Abstract

Van der Waals material CuInP2S6 (CIPS) exhibits room temperature ferroelectricity with unconventional quadruple-well. Here we report the effect of a ferroelectric substrate on the domain formation and piezoelectric response of CIPS. We mechanically exfoliated 8-250 nm CIPS flakes and transferred them on top of Si, Au, and 50 nm epitaxial (001) PbZr0.2Ti0.8O3 (PZT) films. Piezoresponse force microscopy (PFM) studies show spontaneous domain formation in CIPS flakes on Si and Au substrates, while flakes on PZT exhibit uniform polarization that is fully aligned with the pre-patterned domain structures in the underlying PZT. We also performed in-situ PFM studies at elevated temperatures, which reveals an enhanced Curie temperature of  ~200 ºC for CIPS on PZT. We further extracted the piezoelectric coefficient d33 for these samples. The d33 for thin CIPS on PZT is significantly enhanced compared with those on Au and Si, and changes from 10 pm/V for the 8 nm sample to -8 pm/V for flakes thicker than 25 nm. We attribute this result to the shift of Cu cation from the metastable position to the ground state position in the quadruple-energy-well, which is driven by the interfacial polar coupling with PZT. Our study points to a new strategy to engineering the piezoelectric response of CIPS.

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Presenters

  • Kun Wang

    Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln

Authors

  • Kun Wang

    Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln

  • Jia Wang

    Department of Mechanical and Materials Engineering & Nebraska Center for Materials and Nanoscience, University of Nebraska - Lincoln, Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln

  • Yifei Hao

    Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska - Lincoln

  • Xia Hong

    Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska - Lincoln, University of Nebraska-Lincoln, University of Nebraska, Lincoln