Atomic Layer Deposition of Epitaxial Ferroelectric Hf_0.5Zr_0.5O₂ Thin Films

Ferroelectric hafnium oxide has been actively researched as an important class of material and as a candidate for non-volatile memory applications due to its various physical and electrical properties. According to former studies, the origin of ferroelectricity in hafnium oxide can be attributed to the formation of a non-centrosymmetric orthorhombic Pca2₁ phase. Even in a single orthorhombic phase, ferroelectric behavior can be tuned by applying mechanical stress or external fields to the epitaxial film. However, the practical implementation, particularly its epitaxial stabilization and a clearer understanding of its intrinsic ferroelectricity has been a significant challenge. Our study arouses the potential importance of atomic layer deposition (ALD) for mass production in modern industries, demonstrating its proficiency in achieving epitaxial growth of ferroelectric Hf_0.5Zr_0.5O₂ (HZO) thin films on Yttria-stabilized zirconia (YSZ) substrates. Moreover, with distinct ferroelectric switching currents, our work reveals the ferroelectric characteristics of epitaxial HZO thin films deposited through ALD on YSZ-buffered Si substrates, which aligns well with CMOS technology.