Possible Extrinsic Ferroelectric-like Signals Originated from the Oxygen Vacancy Drift in HfO2-Based Films

Abstract

It is generally accepted that oxygen vacancies (VO) 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 a possible extrinsic source of the ferroelectric-like signals. A key finding is that charged VO oscillate within the sample under repeated electric pulses, yielding a nonlinear current which behaves similar 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 agreement with experimental values, given a charged VO concentration in the vicinity of 1 × 1020 cm–3. Moreover, it is possible to exploit this mechanism to reproduce the scattered remnant polarization values and the effects of wake-up, split-up, and limited endurance that are of crucial relevance for the device applications.