LAUSR

Abstract To date, the high energy storage performances observed in the field-induced ferroelectric HfO 2 - or ZrO 2 -based films have had an obstacle to scale-up due to the involvement of low-k monoclinic phase at the large thickness (> ~ 10 nm). Considering that the monoclinic phase formation is closely related with the in-situ (partial) crystallization during the atomic layer deposition (ALD) process, in this work, the ALD temperature of Hf 0.5 Zr 0.5 O 2 thin films was lowered, and its influence on the energy storage performances was systematically examined. Carbon and nitrogen dopants incorporated at a low deposition temperature in combination with grain size decrease change the polymorphism of Hf 0.5 Zr 0.5 O 2 thin film from the genuine ferroelectric to field-induced (incipient) ferroelectric crystal structure. The Hf 0.5 Zr 0.5 O 2 thin film deposited at 210 °C shows improved resistance to degradation by monoclinic phase involvement up to ~ 40 nm compared to the previously-reported Hf 0.3 Zr 0.7 O 2 thin films. By investigating Hf 0.5 Zr 0.5 O 2 thin films with wide ALD temperature and thickness ranges, energy storage density of ~ 55 J cm −3 with an efficiency of ~ 57% can be achieved at the ~ 7.1 nm Hf 0.5 Zr 0.5 O 2 thin films deposited at 215 °C. The performance can be retained even after 10 10 bipolar switching cycles, and the film endures thermal stress up to 175 °C without severe degradation, demonstrating notable reliability.