It is generally accepted that oxygen vacancies play a central role in the emergence of ferroelectricity for HfO2-based materials, but the underlying mechanism still remains elusive. Herein, starting from the basic characterization circuit, we propose that the observed ferroelectricity is extrinsic. A key finding is that charged oxygen vacancies oscillate within the sample under repeated electric pulses, yielding a nonlinear current which behaves similarly to the polarization current for a normal ferroelectric. This unwanted current signal results in a ferroelectric-like hysteresis loop with both remnant polarization and coercive field in good agreements with experimental values, given a charged oxygen vacancy concentration in the vicinity of 1*10^20/cm^3. Moreover, it is possible to exploit this mechanism to reproduce the effects of wake-up, split-up and limited endurance that are of crucial relevance for the device applications.
@article{arxiv.2112.13431,
title = {Extrinsic ferroelectricity originated from oxygen vacancy drift in HfO2-based films},
author = {Yong Cheng and Maoyuan Zheng and Xingwang Zhang and Hao Dong and Yitian Jiang and Jinliang Wu and Jing Qi and Zhigang Yin},
journal= {arXiv preprint arXiv:2112.13431},
year = {2021}
}