Excellent Ferroelectric Properties of Hf0.5Zr0.5O2 Thin Films Induced by Al2O3 Dielectric Layer

The ferroelectricity of Hf _0.5 Zr _0.5 O ₂ (HZO) thin films has been usually reported to be induced by metallic capping layer. In this work, we successfully obtained ferroelectricity of HZO thin films induced by ultrathin insulating Al ₂ O ₃ capping layers. The ferroelectric properties of HZO thin films induced by Al ₂ O ₃ capping layers with different thickness have been investigated. It was found that the Al ₂ O ₃ (2 nm)/HZO (20 nm) stack shows excellent ferroelectric properties. The Au/Al ₂ O ₃ (2 nm)/HZO (20 nm)/TiN capacitor exhibits a very low leakage current of ~ 4.2 × 10 ^-9 A at 4 V and a maximum 2P _r ≈32.3 μC/cm ² at sweeping voltages between ±8 V. In addition, the capacitor also shows excellent endurance properties up to 108 cycles. Our work demonstrated that dielectric films like Al ₂ O ₃ can be adopted to be used as capping layer to generate excellent ferroelectric properties of HfO ₂ -based thin films, which will contribute to their future applications in ferroelectric memory and negative capacitance transistors.