No-heating deposition of ferroelectric epitaxial Hf_0.5Zr_0.5O₂ films using a sputtering method with precise RF power density and thickness control

The no-heating deposition of (111)-oriented epitaxial (Hf_0.5Zr_0.5)O₂ films was successfully achieved on (111) indium tin oxide//(111) yttria-stabilized zirconia substrates using a radio-frequency (RF) magnetron sputtering method. As the RF power density was increased, the crystal phase changed sequentially from the tetragonal, the orthorhombic, and then to the monoclinic phase. A similar trend in the crystal phase was also observed with increasing film thickness. The (Hf_0.5Zr_0.5)O₂ film exhibited ferroelectric properties comparable to the (Y_0.07Hf_0.93)O₂ film previously produced via non-heating film deposition. Upon heat treatment at 1000 ℃, the crystal phase of the film transitioned from the orthorhombic phase to the monoclinic phase, indicating that the stability of the orthorhombic phase is low compared with (Y_0.07Hf_0.93)O₂. Therefore, precise control of the RF power density and film thickness is essential for preparing ferroelectric (Hf_0.5Zr_0.5)O₂ films without heating.