Ferroelectricity of pristine Hf_0.5Zr_0.5O₂ films fabricated by atomic layer deposition

Hafnium-based ferroelectric films, remaining their ferroelectricity down to nanoscale thickness, present a promising application for low-power logic devices and nonvolatile memories. It has been appealing for researchers to reduce the required temperature to obtain the ferroelectric phase in hafnium-based ferroelectric films for applications such as flexible and wearable electronics. This work demonstrates that a remanent polarization (P_r) value of < 5 μC/cm² can be obtained in as-deposited Hf_0.5Zr_0.5O₂ (HZO) films that are fabricated by thermal atomic layer deposition (TALD) under low temperature of 250 °C. The ferroelectric orthorhombic phase (o-phase) in the as-deposited HZO films is detected by scanning transmission electron microscopy (STEM). This low fabrication temperature further extends the compatibility of ferroelectric HZO films to flexible electronics and avoids the cost imposed by following high-temperature annealing treatments.