Bistable State of Protons for Low-Voltage Memories
Xian‐Jiang Song, Zhi‐Xu Zhang, Xiao‐Gang Chen, Han‐Yue Zhang, Qiang Pan, Jie Yao, Yu‐Meng You, Ren‐Gen Xiong
Abstract
Molecular ferroelectrics are attracting tremendous interest because of their easy and environmental-friendly processing, low acoustic impedance, and mechanical flexibility. Their ferroelectric mechanism is mainly ascribed to the order–disorder transition of molecules such as spherical 1,4-diazabicyclo[2.2.2] octane (DABCO) and quinuclidine. Here, we present two molecular ferroelectrics, [HDABCO][TFSA] and its deuterated one [DDABCO][TFSA] (TFSA = bis(trifluoromethylsulfonyl)ammonium), whose ferroelectricity is triggered by the proton ordering. This is the first time that the protons show a thermally fluctuated bistability with a double-well potential in DABCO-based ferroelectrics. A large deuterium isotope effect (ΔT = ∼53 K) not only proves that they are hydrogen-bonded ferroelectrics but also extends the ferroelectric working temperature range to room temperature. The superfast polarization switching of 100 kHz and ultralow coercive voltage of 1 V (far less than 5 V required for commercially available ferroelectric devices), benefiting from the low energy for proton transfer, allow [DDABCO][TFSA] a great potential for memory devices with low-voltage, high-speed operation. This work should inspire further exploration of hydrogen-bonded molecular ferroelectrics for flexible and wearable devices with the low-power information storage.