The effects of oxygen in spinel oxide Li1+xTi2-xO4-delta thin films

TL;DR

This study investigates how varying oxygen pressure during fabrication influences the structural, electronic, and superconducting properties of Li1+xTi2-xO4-delta thin films, revealing a transition from superconducting to insulating phases.

Contribution

It provides a detailed analysis of oxygen's role in tuning the phase and properties of LiTi2O4-delta thin films, including the transition to Li4Ti5O12 and the associated structural changes.

Findings

Oxygen vacancies are filled with increasing oxygen pressure.

The c-axis lattice constant decreases and stabilizes at a critical oxygen pressure.

Magnetoresistance behavior changes non-monotonically with oxygen pressure.

Abstract

The evolution from superconducting LiTi2O4-delta to insulating Li4Ti5O12 thin films has been studied by precisely adjusting the oxygen pressure during the sample fabrication process. In the superconducting LiTi2O4-delta films, with the increase of oxygen pressure, the oxygen vacancies are filled, and the c-axis lattice constant decreases gradually. With the increase of the oxygen pressure to a certain critical value, the c-axis lattice constant becomes stable, which implies that the Li4Ti5O12 phase comes into being. The process of oxygen filling is manifested by the angular bright-field images of the scanning transmission electron microscopy techniques. The temperature of magnetoresistance changed from positive and negative shows a non-monotonous behavior with the increase of oxygen pressure. The theoretical explanation of the oxygen effects on the structure and superconductivity of LiTi2O4-delta has also been discussed in this work.