Ferroelectricity in Orthorhombic Zirconia Thin Films

Ferroelectric fluorite oxides such as hafnium (HfO₂)-based materials are one of the most promising candidates for future large-scale integrated circuits (ICs), while zirconia (ZrO₂)-based fluorite materials, which have the same structure as HfO₂ and more abundant resources and lower cost of raw materials, are usually thought to be anti- or ferroelectric-like. Here, we report a remanent polarization (P_r) of ∼15 μC/cm² in orthorhombic ZrO₂ thin films at 77 K. This ferroelectricity arises from an electric field-induced antiferroelectric to ferroelectric phase transition, which is particularly noticeable at 77 K. Our work reveals the ferroelectricity in ZrO₂ thin films and offers a new pathway to understand the origin of ferroelectricity in fluorite oxides.