DFT+U simulation of the Ti${}_4$O${}_7$-TiO${}_2$ interface

TL;DR

This study uses DFT+U simulations to analyze the Ti${}_4$O${}_7$-TiO${}_2$ interface, revealing a type II band alignment where Ti${}_4$O${}_7$ acts as an electron donor to TiO${}_2$, which is crucial for memristor behavior.

Contribution

The paper introduces a method to model and analyze the interface between Ti${}_4$O${}_7$ and TiO${}_2$, providing new insights into their electronic band alignment.

Findings

The interface exhibits a type II band alignment.

Ti${}_4$O${}_7$ acts as a donor to TiO${}_2$.

Band offset details inform memristor conduction mechanisms.

Abstract

The formation of conducting channels of Ti${}_4$O${}_7$ inside TiO${}_2$-based memristors is believed to be the origin for the change in electric resistivity of these devices. While the properties of the bulk materials are reasonably known, the interface between them has not been studied up to now mostly due to their different crystalline structures. In this work we present a way to match the interfaces between TiO${}_2$ and Ti${}_4$O${}_7$ and subsequently the band offset between these materials is obtained from density functional theory based calculations. The results show that while the valence band is located at the Ti${}_4$O${}_7$, the conduction band is found at the TiO${}_2$ structure, resulting into a type II interface. In this case, the Ti${}_4$O${}_7$ would act as a donor to the TiO${}_2$ matrix.