Enabling Low Coercive Voltage in Hf_0.5Zr_0.5O₂/BaTiO₃ Heterostructure via Double Ferroelectric Coupling

In recent years, hafnium-based binary oxides, particularly Hf_0.5Zr_0.5O₂ (HZO), have garnered significant attention due to their stable ferroelectric properties at the nanoscale and compatibility with Complementary Metal-Oxide Semiconductor (CMOS) devices. However, maintaining ferroelectricity at extremely thin thicknesses is often hindered by a substantial coercive field, limiting the applicability of ferroelectric HZO in low-power applications. Typically, reducing the operating voltage compromises the stability of ferroelectric polarization. In this context, we introduce a novel approach to achieve lower operating voltage by creating a heterostructure consisting of perovskite/fluorite ferroelectric layers. When compared to fluorite ferroelectrics, perovskite ferroelectrics, such as BaTiO₃ (BTO) thin films, exhibit a significantly lower coercive field. In our study, we showcase the high-quality heterostructure of BTO/HZO, which is fabricated by pulsed laser deposition, and we characterize the ferroelectric properties through piezo force microscopy and a ferroelectric tester. By incorporating the low-voltage switchable BTO layer, we have the potential to induce critical domain nucleation in the BTO layer, leading to a lower switching voltage for the HZO layer. This innovative approach leverages the advantages of both materials to address the challenges associated with high switching voltages in HZO and the integration of perovskite ferroelectrics into the CMOS process. Our findings may pave the way for enhanced performance and efficiency in ferroelectric-based devices, such as Ferroelectric Field-Effect Transistors (Fe-FETs) and Ferroelectric Tunnel Junctions (FTJs).