Scale-up and optimization of HfO2-ZrO2 solid solution thin films for the electrostatic supercapacitors

To date, the high energy storage performances observed in the field-induced ferroelectric HfO2- or ZrO2-based films have had an obstacle to scale-up due to the involvement of low-k monoclinic phase at the large thickness (> similar to 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 Hf0.5Zr0.5O2 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 Hf0.5Zr0.5O2 thin film from the genuine ferroelectric to field-induced (incipient) ferroelectric crystal structure. The Hf0.5Zr0.5O2 thin film deposited at 210 degrees C shows improved resistance to degradation by monoclinic phase involvement up to similar to 40 nm compared to the previously-reported Hf0.3Zr0.7O2 thin films. By investigating Hf0.5Zr0.5O2 thin films with wide ALD temperature and thickness ranges, energy storage density of similar to 55 J cm(-3) with an efficiency of similar to 57% can be achieved at the similar to 7.1 nm Hf0.5Zr0.5O2 thin films deposited at 215 degrees C. The performance can be retained even after 10(10) bipolar switching cycles, and the film endures thermal stress up to 175 degrees C without severe degradation, demonstrating notable reliability.