context: The listed physical parameters are essential for designing a new generation of electronic devices with significantly improved sensitivity and time response. For instance, the high piezoelectric activity of near room temperature ferroelectrics Sn2P2S6, whose Tc ≈ 337 K, can compete with well-known BiFeO3, currently one of the top choices for switchable ferroelectric diodes. Near room temperature spontaneous polarization of Sn2P2S6 can serve as a base for non-volatile ferroelectric random-access memory (FERAM) elements, at the same time significantly miniaturizing the designed systems. The first steps of such practical exploits have been recently observed for layered room-temperature ferroelectric CuInP2S6, demonstrating that reversible polarization switchability with an on/off ratio of about ∼100 can be achieved for ferroelectric flakes with the thickness reaching an impressive limit of ∼4 nm. Due to locally controlled ion conductivity and giant negative electrostrictive coefficients, CuInP2S6 is also considered as a solid electrolyte for boosting sodium and lithium battery performance. Similarly, 2D superparaelectric Sn2P2S6 with a large dielectric constant was also proposed for the same purpose. The high photoelectric conversion efficiency of Sn2P2S6 allowed exploration of the ultrafast shift-current behaviour, comparable only to the performance of SbSI, CdSe, and CdS. These properties can be utilised for the novel design of the band edge shift current based photovoltaic devices, pushing the solar cell energy harvesting towards their theoretical limit. Additionally, Sn2P2S6 ferroelectrics have prominent photorefractive properties in the near-infrared spectral region, which makes them suitable for highly efficient acousto-optic and holographic devices.
answer: CuInP2S6