Composition-Dependent Ferroelectric Properties in Sputtered Hf X Zr 1−X O 2 Thin Films

Ferroelectric materials with a perovskite structure have various shortcomings, including poor Si compatibility, large physical thickness, and small bandgap. HfO2-based ferroelectric materials provide a new solution for ferroelectric semiconductor devices. HfO2-ZrO2solid solution (HZO) thin films have been widely studied due to their low crystallization temperature and wide stoichiometric range. Considering its low cost and flexible deposition conditions, the sputtering technique is a useful method for HZO deposition. However, sputtered HZO ferroelectric films have been rarely reported, and the composition effect on the ferroelectric properties of HfXZr1-XO2thin films is still unclear. In this letter, sputtered HfXZr1-XO2thin films were studied with different Zr contents (from 12.49 to 20.34 mol%) by varying the sputtering power ratio of ZrO2to HfO2. We found that the dopant concentration with the best ferroelectric properties in the HfXZr1-XO2system is ~15-16 mol%, which is much lower than that in the ALD-based HZO film. First-principle calculation shows that oxygen vacancies doped in the HZO film lead to a change in the Helmholtz free energy of different phases, which affected the optimal Zr concentration for the largest ferroelectric polarization.