Ferroelectricity and Piezoelectricity in 2D Van der Waals CuInP2S6 Ferroelectric Tunnel Junctions

Tingting Jia; Yanrong Chen; Yali Cai; Wenbin Dai; Chong Zhang; Liang Yu; Wenfeng Yue; Hideo Kimura; Yingbang Yao; Shuhui Yu; Quansheng Guo; Zhenxiang Cheng

doi:10.3390/nano12152516

Ferroelectricity and Piezoelectricity in 2D Van der Waals CuInP₂S₆ Ferroelectric Tunnel Junctions

Nanomaterials (Basel). 2022 Jul 22;12(15):2516. doi: 10.3390/nano12152516.

Authors

Tingting Jia^{1

2}, Yanrong Chen^{1

3}, Yali Cai^{1

2}, Wenbin Dai^{1

3}, Chong Zhang^{1

2}, Liang Yu^{1

4}, Wenfeng Yue^{1

4}, Hideo Kimura⁵, Yingbang Yao³, Shuhui Yu¹, Quansheng Guo², Zhenxiang Cheng⁶

Affiliations

¹ Institute of Advanced Materials Science and Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.
² School of Materials Science and Engineering, Hubei University, Wuhan 430062, China.
³ School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, China.
⁴ Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215125, China.
⁵ School of Environmental and Material Engineering, Yantai University, Yantai 264005, China.
⁶ Institute for Superconducting & Electronic Materials, University of Wollongong, Innovation Campus, North Wollongong, NSW 2500, Australia.

Abstract

CuInP2S6 (CIPS) is a novel two-dimensional (2D) van der Waals (vdW) ferroelectric layered material with a Curie temperature of T_C~315 K, making it promising for great potential applications in electronic and photoelectric devices. Herein, the ferroelectric and electric properties of CIPS at different thicknesses are carefully evaluated by scanning probe microscopy techniques. Some defects in some local regions due to Cu deficiency lead to a CuInP2S6-In_4/3P₂S₆ (CIPS-IPS) paraelectric phase coexisting with the CIPS ferroelectric phase. An electrochemical strain microscopy (ESM) study reveals that the relaxation times corresponding to the Cu ions and the IPS ionospheres are not the same, with a significant difference in their response to DC voltage, related to the rectification effect of the ferroelectric tunnel junction (FTJ). The electric properties of the FTJ indicate Cu⁺ ion migration and propose that the current flow and device performance are dynamically controlled by an interfacial Schottky barrier. The addition of the ferroelectricity of CIPS opens up applications in memories and sensors, actuators, and even spin-orbit devices based on 2D vdW heterostructures.

Keywords: ferroelectric properties; negative piezoelectricity; phase segregation; scanning probe microscope; two-dimensional materials.

Abstract

Grants and funding