Hafnium oxide–based ferroelectric materials emerged as promising candidates for constructing next-generation high-density memory devices due to their silicon compatibility. However, the high coercive field (E_c, typically exceeding 1.0 MV/cm) puts forward challenges to high operating voltage and limited endurance performance. To overcome these limitations, a strategy is utilized by applying an in-situ direct current electric field during rapid thermal process (RTP). This approach enables simultaneous reduction of coercive field and enhancement of ferroelectric polarization in Hf_0.5Zr_0.5O₂ (HZO). Notably, a record-low E_c (~0.79 MV/cm) is achieved among atomic layer deposition-grown Zr-doped HfO₂ ferroelectric films, facilitating lower operation voltage, faster switching speed, and improved endurance characteristics. High-resolution transmission electron microscopy analysis reveals that the ferroelectric domains in samples through electric field assisted-RTP exhibit a relatively preferential out-of-plane orientation compared to normal RTP-treated samples, which is the underlying mechanism in reducing the coercive field and enhancing ferroelectric polarization. This study introduces a practical and effective method for optimizing the overall performance of HZO films, underscoring their potential for application in non-volatile memory technologies.

The superior dielectric and ferroelectric properties of HfO₂-based thin films, coupled with excellent silicon compatibility, position them as highly attractive candidates for dynamic and ferroelectric random-access memories (DRAM and FeRAM). However, simultaneously achieving high dielectric constant (κ) and strong ferroelectricity in HfO₂-based films presents a challenge, as high-κ and ferroelectricity are associated with the tetragonal and orthorhombic phases, respectively. In this study, we report both the good ferroelectric and dielectric properties obtained in W/Hf_0.5Zr_0.5O₂ (HZO ~6.5 nm)/W with morphotropic phase boundary structure by optimizing stacking sequence of HfO₂ and ZrO₂ sublayers. Notably, by alternating stacking of 1-cycle HfO₂ with 1-cycle ZrO₂ sublayers ((1–HfO₂)/(1–ZrO₂)), high-κ (>50) and large polarization (2P_r > 40 μC/cm², after wake-up) can be achieved. Besides, the (1–HfO₂)/(1–ZrO₂) stacking configuration presents better thermal stability compared to other stacking sequences. Furthermore, the incorporation of an Al₂O₃ layer leads to a low leakage current density (<10⁻⁷ A/cm² at 0.65 V) and high dielectric endurance over 10¹³ cycles (operating voltage ~0.5 V). A low equivalent oxide thickness (EOT ~0.53 nm) and considerable polarization with low leakage are simultaneously achieved. These results highlight the potential of HfO₂-based films with optimized structural stacking as a trade-off approach for integrating DRAM and FeRAM on one-chip.

Flexible hafnia-based ferroelectric memories are arousing much interest with the ever-growing demands for nonvolatile data storage in wearable electronic devices. Here, high-quality flexible Hf_0.5Zr_0.5O₂ membranes with robust ferroelectricity were fabricated on inorganic pliable mica substrates via an atomic layer deposition technique. The flexible Hf_0.5Zr_0.5O₂ thin membranes with a thickness of -8 nm exhibit a high remanent polarization of -16 μC/cm², which possess very robust polarization switching endurance (>10¹⁰ cycles, two orders of magnitude better than reported flexible HfO₂-based films) and superior retention ability (expected >10 years). In particular, stable ferroelectric polarization as well as excellent endurance and retention performance show negligible degradations under 6 mm radius bending conditions or after 10⁴ bending cycles with a 6 mm bending radius. These results mark a crucial step in the development of flexible hafnium oxide-based ferroelectric memories for wearable electronic devices.