First Observation of Negative Capacitance in Molecular Ferroelectric Thin Films

On the path of persisting Moore's Law, one of the biggest obstacles is the "Boltzmann tyranny," which defines the lower limit of power consumption of individual transistors. Negative capacitance (NC) in ferroelectrics could provide a solution and has garnered significant attention in the fields of nanoelectronics, materials science, and solid-state physics. Molecular ferroelectrics, as an integral part of ferroelectrics, have developed rapidly in terms of both performance and functionality, with their inherent advantages such as easy fabrication, mechanical flexibility, low processing temperature, and structural tunability. However, studies on the NC in molecular ferroelectrics are limited. In this study, the focus is centered on the fabricated high-quality thin films of trimethylchloromethyl ammonium trichlorocadmium(II), and a pioneering investigation on their NC responses is conducted. The findings demonstrate that the NC exhibited by molecular ferroelectrics is comparable to that of conventional HfO2-based ferroelectrics. This underscores the potential of molecular material systems for next-generation electronic devices. A significant negative capacitance response is directly observed in the thin film of molecular ferroelectric trimethylchloromethyl ammonium trichlorocadmium. When compared to conventional inorganic ferroelectrics, molecular ferroelectrics, in which order-disorder transition of the molecular induces the occurrence of polarization, would have a smaller ferroelectric anisotropy parameter alpha and a larger domain wall formation energy.image