Deterministic Role of Concentration Surplus of Cation Vacancy over Anion Vacancy in Bipolar Memristive NiO

TL;DR

This study demonstrates that a surplus of Ni vacancies over O vacancies in NiO films governs bipolar memristive switching, supporting a dual-defects model and offering new insights into memristor mechanisms beyond oxygen vacancy effects.

Contribution

It provides experimental evidence for the role of cation and anion vacancy imbalance in memristive switching, advancing understanding beyond traditional oxygen vacancy models.

Findings

Ni vacancy surplus determines bipolar switching

Supports dual-defects-based memristor model

Introduces methodology to study dual defect effects

Abstract

Migration of oxygen vacancies has been proposed to play an important role in the bipolar memristive behaviors since oxygen vacancies can directly determine the local conductivity in many systems. However, a recent theoretical work demonstrated that both migration of oxygen vacancies and coexistence of cation and anion vacancies are crucial to the occurrence of bipolar memristive switching, normally observed in the small-sized NiO. So far, experimental work addressing this issue is still lacking. In this work, with conductive atomic force microscope and combined scanning transmission electron microscopy & electron energy loss spectroscopy, we reveal that concentration surplus of Ni vacancy over O vacancy determines the bipolar memristive switching of NiO films. Our work supports the dual-defects-based model, which is of fundamental importance for understanding the memristor mechanisms beyond the well-established oxygen-vacancy-based model. Moreover, this work provides a methodology to investigate the effect of dual defects on memristive behaviors.