Controlling the Wake-Up Mechanism and Switching Kinetics of Ferroelectric Hf _<i>x</i> Zr _{1 –  <i>x</i>} O ₂ through Hf Content Modulation

The excellent scalability and compatibility to current CMOS manufacturing processes make ferroelectric Hf_<i>x</i>Zr_{1 -} <i>_x</i>O₂ thin films a promising candidate for embedded nonvolatile memories, as well as for synaptic devices in neuro-inspired computing. In order to achieve precise control over the polarization states and to ensure reliable operation in these thin films, a thorough understanding of the film's domain switching kinetics and behavior under field cycling is necessary. The Hf composition in Hf_<i>x</i>Zr_{1 - <i>x</i>}O₂ thin films plays a crucial role in determining the disorders, phase composition, and crystallographic texture within the film when integrated in a metal-ferroelectric-metal (MFM) device, all of which affect the evolution of its field cycling response and switching kinetics. In this work, the impact of Hf content on wake-up and domain switching kinetics in Hf_<i>x</i>Zr_{1 - <i>x</i>}O₂ thin films is investigated, and the physical mechanisms behind these differences are explored. This study highlights that multiple wake-up mechanisms can coexist in the same film and that as the Hf composition is increased, the dominant physical mechanism of wake-up in the film changes from a field-induced phase transition to field-induced ferroelastic domain switching. Furthermore, since the inhomogeneity within the ferroelectric film depends on Hf composition, the speed of polarization switching and the available partial polarization states in the film can be precisely controlled as a function of Hf content due to the disorder-driven domain nucleation and nonlinear domain wall dynamics.