Nanocomposites and nanomaterials

Phase transitions in van der Waals ferroics CuInP2S(Se)6 
and their applications
Vysochanskii Yu., Glukhov K., Hryts V., Shiposh Yu., Kundria M.,
Medulych M., Kohutych A., Yevych R. 
Institute for Solid State Physics and Chemistry, Uzhhorod University, Pidgirna Str. 46, 88000 Uzhhorod, Ukraine
E-mail: vysochanskii@gmail.com

For van der CuInP2S(Se)6 crystals with ferrielectric or antiferroelectric ordering the possibility of spontaneous polarization switching in samples with a thickness of several structural layers were observed [1,2]. This discovering opened a new direction of research in the field of nanoelectronics based on van der Waals multiferroics. The created ferroelectric diode based on CuInP2S6 demonstrates non-volatile memory and indicates the possibility of integration with well-established silicon technologies [2]. In the CuInP2S6/germanene heterostructure a change in the direction of spontaneous polarization induces a semiconductor-metal transition and can be used in the development of non-volatile ferroelectric switches and memory devices [3]. On the heterostructure MoS2–CuInP2S6 has been implemented [4] as a field-effect transistor with negative capacitance.
Comparative analysis of DFT calculated electron and phonon spectra, experimental Raman scattering data at different temperatures and pressures together with simulations in four – well quantum anharmonic oscillators model characterizes anharmonic dynamics of copper and indium sublattices in CuInP2S(Se)6 crystals. In this background, the nature of phase transitions, polar ordering, and is important for application characteristics are analyzed. 

1.	Belianinov A., He Q., Dziaugys A., Maksymovych P., Eliseev E., Borisevich A., Morozovska A., Banys J., Vysochanskii Yu., Kalinin S.. CuInP2S6 room temperature layered ferroelectric // Nano Lett. – 2015. - 15 (6). - P. 3808 - 3814.
2.	Fucai Liu e.a. Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes // Nature Communications. – 2016. – 7. – P. 12357-1 – 12357-6.
3.	Ziye Zhu e.a. Electric field control of the semiconductor-metal transition in two-dimensional CuInP2S6/germanene van der Waals heterostructure // Appl. Phys. Lett. – 2019. – 114. – P. 223102-1 – 223102-5.
4.	Xiaowei Wang e.a. Van der Waals negative capacitance transistors // Nature Communications. – 2019. – 10. – P. 3037-1 – 3037-8.