Observing suppressed polarization in flexible ferroelectric negative capacitance field effect transistors

Negative capacitance (NC) has the potential to enable low power microelectronics beyond the fundamental thermionic limit, and it has been theorized that the thermodynamically unstable NC of ferroelectrics can be stabilized by linear dielectric, making negative capacitance ferroelectric field effect transistors (NC-FeFET) possible. Nevertheless, the validity of NC as a physical concept for ferroelectrics remain contentious despite numerous theoretical and experimental investigations, and the intrinsic ferroelectric NC with suppressed polarization has not been demonstrated except locally at vortex core. While NC-FeFET with subthreshold swing (SS) lower than 60 mV/dec limit has been reported, such device characteristics has not been directly connected to suppressed polarization at materials' level, and alternative mechanisms other than NC have also been proposed. Here we demonstrate stable sub-60 mV/dec SS with hysteresis free I—V in NC-FeFET based on SrTiO₃/Pb(Zr_0.1Ti_0.9)O₃/SrTiO₃ heterostructure, and observe its suppressed polarization at both macroscopic and microscopic scales. The intrinsic ferroelectric NC thus is experimentally confirmed and directly connected to NC-FeFET performance, and the mica-based device is also highly flexible and robust under cyclic bending as well as extended heating.