Termination-Dependent Resistive Switching in SrTiO$_3$ Valence Change Memory Cells

TL;DR

This study uses atomistic and ab initio modeling to explore how the termination of SrTiO$_3$ influences interface-type resistive switching in VCM cells, highlighting the role of oxygen vacancies and band alignment.

Contribution

It provides a detailed atomistic understanding of termination-dependent resistive switching mechanisms in SrTiO$_3$ based VCM cells, which was previously not well understood.

Findings

Termination of SrTiO$_3$ critically affects switching behavior.

Oxygen vacancy accumulation at the Pt side influences conduction.

Filamentary switching is likely at the Pt electrode of SrO-terminated cells.

Abstract

Valence change memory (VCM) cells based on SrTiO$_3$ (STO), a perovskite oxide, are a promising type of emerging memory device. While the operational principle of most VCM cells relies on the growth and dissolution of one or multiple conductive filaments, those based on STO are known to exhibit a distinctive, 'interface-type' switching, which is associated with the modulation of the Schottky barrier at their active electrode. Still, a detailed picture of the processes that lead to interface-type switching is not available. In this work, we use a fully atomistic and ab initio model to study the resistive switching of a Pt-STO-Ti stack. We identify that the termination of the crystalline STO plays a decisive role in the switching mechanism, depending on the relative band alignment between the material and the Pt electrode. In particular, we show that the accumulation of oxygen vacancies at the Pt side can be at the origin of resistive switching in TiO$_2$-terminated devices by lowering the conduction band minimum of the STO layer, thus facilitating transmission through the Schottky barrier. Moreover, we investigate the possibility of filamentary switching in STO and reveal that it is most likely to occur at the Pt electrode of the SrO-terminated cells.