In-depth Understanding of Polarization Switching Kinetics in Polycrystalline $\mathbf{Hf}_{0.5} \mathbf{Zr}_{0.5} \mathbf{O}_{2}$ Ferroelectric Thin Film: A Transition From NLS to KAI
Wei Wei, Weiqiang Zhang, Lu Tai, Guoqing Zhao, Pengpeng Sang, Qianwen Wang, Fei Chen, Mingfeng Tang, Yang Feng, Xuepeng Zhan, Qing Luo, Yuan Li, Jiezhi Chen
Abstract
To achieve deep insights into the polarization switching kinetics in ferroelectric <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Hf}0.5\text{Zr}0.5\mathrm{O}_{2}$</tex> (HZO), the intrinsic switching characteristics are measured accurately by using a novel pulse sequence to eliminate the charge trapping, polarization unsaturation and imprint effects. By NLS fittings, the average switching time and the concentration of pinning sites are extracted, with main focus on their dependences on the external electric field, the electrode size <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$l$</tex> and the temperature <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$T$</tex> . Although the average switching time shows weak dependence on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$T,$</tex> , it decreases sharply with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$l$</tex> scaling and sub-ns switching behavior is predicted at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$l\leq 3.89\mu \mathrm{m}$</tex> . More importantly, our observations intensely imply that a transition happens from NLS to KAI model when <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$T$</tex> is below 161K or <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$l$</tex> is approaching the grain size (10~30nm). This surprised but reasonable transition indicates that, as scaling the ferroelectric memory size or for operations under cryogenic temperatures, HZO ferroelectrics can switch much faster and more uniform.