Tailoring Materials for Mottronics: Excess Oxygen Doping of a Prototypical Mott Insulator

TL;DR

This paper demonstrates that excess oxygen doping in LaTiO₃ thin films can effectively tune the material across the Mott transition, enabling potential applications in Mottronics devices by controlling the insulator-metal phase change.

Contribution

It introduces a method to control the Mott insulator LaTiO₃ via oxygen doping, enabling reversible switching near the metal-insulator transition.

Findings

Excess oxygen doping induces a strong insulator-metal transition.

Stable LaTiO₃₊ₓ films can be achieved with substrate and capping layer control.

Resistivity changes by several orders of magnitude during transition.

Abstract

The Mott transistor is a paradigm for a new class of electronic devices---often referred to by the term Mottronics---, which are based on charge correlations between the electrons. Since correlation-induced insulating phases of most oxide compounds are usually very robust, new methods have to be developed to push such materials right to the boundary to the metallic phase in order to enable the metal-insulator transition to be switched by electric gating. Here we demonstrate that thin films of the prototypical Mott insulator LaTiO$_3$ grown by pulsed laser deposition under oxygen atmosphere are readily tuned by excess oxygen doping across the line of the band-filling controlled Mott transition in the electronic phase diagram. The detected insulator to metal transition is characterized by a strong change in resistivity of several orders of magnitude. The use of suitable substrates and capping layers to inhibit oxygen diffusion facilitates full control of the oxygen content and renders the films stable against exposure to ambient conditions, making LaTiO$_{3+x}$ a promising functional material for Mottronics devices.