Conducting interface in oxide homojunction: understanding of superior properties in black TiO2

TL;DR

This study fabricates TiO2 homojunction films to investigate the mechanisms behind black TiO2's superior optoelectronic properties, revealing that metallic conduction at the interface is key to its enhanced performance.

Contribution

It provides the first detailed understanding of black TiO2's properties by simulating its structure with TiO2 homojunctions and identifying interface reconstruction as the main factor.

Findings

Metallic conduction occurs at the crystalline-amorphous interface.

Interface reconstruction is the primary reason for black TiO2's superior properties.

The work offers new insights into carrier behavior at oxide interfaces.

Abstract

Black TiO2 nanoparticles with a crystalline-core and amorphous-shell structure exhibit superior optoelectronic properties in comparison with pristine TiO2. The fundamental mechanisms underlying these enhancements, however, remain unclear, largely due to the inherent complexities and limitations of powder materials. Here, we fabricate TiO2 homojunction films consisting of an oxygen-deficient amorphous layer on top of a highly crystalline layer, to simulate the structural/functional configuration of black TiO2 nanoparticles. Metallic conduction is achieved at the crystalline-amorphous homointerface via electronic interface reconstruction, which we show to be the main reason for the superior properties of black TiO2. This work not only achieves an unprecedented understanding of black TiO2, but also provides a new perspective for investigating carrier generation and transport behavior at oxide interfaces, which are of tremendous fundamental and technological interest.