The realization of high-Q resonances in a silicon metasurface with various broken-symmetry blocks is reported. Theoretical analysis reveals that the sharp resonances in the metasurfaces originate from symmetry-protected bound in the continuum (BIC) and the magnetic dipole dominates these peculiar states. A smaller size of the defect in the broken-symmetry block gives rise to the resonance with a larger Q factor. Importantly, this relationship can be tuned by changing the structural parameter, resulting from the modulation of the topological configuration of BICs. Consequently, a Q factor of more than 3,000 can be easily achieved by optimizing dimensions of the nanostructure. At this sharp resonance, the intensity of the third harmonic generation signal in the patterned structure can be 368 times larger than that of the flat silicon film. The proposed strategy and underlying theory can open up new avenues to realize ultrasharp resonances, which may promote the development of the potential meta-devices for nonlinearity, lasing action, and sensing.

HfO ₂ -ZrO ₂ superlattice (SL) ferroelectric (FE) capacitor is demonstrated to have improved endurance performance and higher fatigue recovery capability compared to the HfZrO _x (HZO) device. During the cycling of polarization ( ${P}$ ) vs. voltage ( ${V}$ ) loops, the SL metal-FE-metal (MFM) capacitor exhibits the higher ${P}$ and the lower leakage current over the HZO device indicating the lower defect density in SL. The SL capacitor achieves an endurance of ${5}\times {10} ^{{12}}$ cycles, which is three orders of magnitude higher than the HZO device. The ${P}$ fatigue of the SL capacitor can be fully recovered through a ~30 s break, and that of HZO is only partially recovered utilizing the higher field cycling. This is because the trapping/detrapping process significantly decreases in HfO ₂ -ZrO ₂ SL over HZO capacitor by the reduced defect density. These results prove that the HfO ₂ -ZrO ₂ SL is a promising technology for endurance unlimited FE random access memory.

In this article, a phase-field polarization switching model for ferroelectric HfO ₂ -based thin films considering oxygen vacancies ( ${V}_{o}$ ) has been developed based on the 2-D time-dependent Ginzburg–Landau (TDGL) equation coupling with Poisson’s equation. The impacts of nonuniform ${V}_{o}$ distributions induced by the monolayer grains in ultra-scaled Hf _0.5 Zr _0.5 O ₂ (HZO) films and ${V}_{o}$ concentrations on ferroelectric characteristics are investigated in detail by the developed model which is verified and calibrated by measurement results of HZO. Furthermore, possible mechanisms of wake-up and fatigue are revealed by the simulation with the proposed model. It is clarified that the redistribution of nonuniform ${V}_{o}$ in the in-plane direction leads to the transition from a pinched polarization-voltage curve to a conventional one at the early stage of wake-up, while the generation of ${V}_{o}$ within a ferroelectric film results in ferroelectricity enhancement and reduction in wake-up and fatigue processes, respectively.

We demonstrate for the first time ZrO2 ferroelectric field-effect transistors (FeFETs) for em-bedded non-volatile memory applications. Multiple sweeps of polarization vs. voltage measurement demonstrate that a metal/ZrO2/Ge capacitor is entirely free of wake-up effect and has significantly improved fatigue characteristics compared to a HfZrOx control device. Thanks to relatively small remnant polariza-tion and a high-quality ZrO2/Ge interface, up to 107 cycles program/erase endurance, 10 ns program/erase speed, and >10-year data retention at 85°C are achieved.