Robustly stable intermediate memory states in HfO_(2)-based ferroelectric field-effect transistors

Multilevel ferroelectric field-effect transistors(FeFETs)integrated with HfO_(2)-based ferroelectric thin films demonstrate tremendous potential in high-speed massive data storage and neuromorphic computing applications.However,few works have focused on the stability of the multiple memory states in the HfO_(2)-based FeFETs.Here we firstly report the write/read disturb effects on the multiple memory states in the Hf_(0.5)Zr_(0.5)O_(2)(HZO)-based FeFETs.The multiple memory states in HZO-based FeFETs do not show obvious degradation with the write and read disturb cycles.Moreover,the retention characteristics of the intermediate memory states in HZO-based FeFETs with unsaturated ferroelectric polarizations are better than that of the memory state with saturated ferroelectric polarization.Through the deep analysis of the operation principle of in HZO-based FeFETs,we speculate that the better retention properties of intermediate memory states are determined by the less ferroelectric polarization degradation and the weaker ferroelectric polarization shielding.The experimental and theoretical evidences confirm that the long-term stability of the intermediate memory states in HZO-based FeFETs are as robust as that of the saturated memory state,laying a solid foundation for their practical applications.

Non-fragile memory feedback control for uncertain time-varying delay switched fuzzy systems with unknown nonlinear disturbance

Currently,the feedback control rate of most nonlinear systems is realised by the memoryless state feedback controller which cannot affect the impact of time delay on the systems,and the general processing method of the Lyapunov–Krasovskii functional for the time-varying delay switched fuzzy systems(SFS)is more conservative.Therefore,this paper addresses the problem of nonfragile robust and memory state feedback control for switched fuzzy systems with unknown nonlinear disturbance.Non-fragile memory state feedback robust controller which has two controller gains different from each other,and switching law are designed to keep the proposed systems asymptotically stable for all admissible parameter uncertainties.Delay-dependent less conservative sufficient conditions are obtained through using the Lyapunov–Krasovskii functional method and free-weighting matrices depending on Leibniz–Newton,guaranteeing that the SFS can be asymptotically stable.A numerical example is given to illustrate the proposed controller performs better than the classic memoryless state feedback controller.