Oxygen‐Driven Metal–Insulator Transition in SrNbO₃ Thin Films Probed by Infrared Spectroscopy

Abstract

addition to this strategy, the electronic and magnetic properties of these oxides, as well as the performance of devices based on their use, are also extremely sensitive to the oxygen content in the lattice. For example, oxygen vacancies acting as shallow donors can drastically affect the number of conducting electrons and have a significant role in the catalytic properties of perovskites, [4] while p-doping through hosting excess oxygen ions in the lattice was demonstrated as an effective way to modulate the band-filling of 3d valence states, [5] and bias-induced drifting of oxygen ions in/ out of the perovskite modifies significantly the resistance of memristive devices in the boundary region among the oxide and the metal electrode. [6,7] At variance with the most explored 3d compounds, for the isostructural perovskites hosting 4d transition metal ions the more extended 4d electronic states in the B-site provide larger hybridization with the surrounding oxygen ions and weaker on-site Coulomb repulsion, thus promoting stronger metallic behavior and reduced electronic correlation effects. In particular, strontium niobate SrNbO 3 (SNO, Nb 4d 1 nominal valence) has recently attracted a lot of interest as a promising visible-light photocatalysts for water splitting, [8][9][10] and as a transparent conductor in the visible and ultraviolet spectra, which makes it an ideal electrode material for high-performance UV light emitting diodes and for plasmonics. [11][12][13] Moreover,The occurrence of oxygen-driven metal-insulator-transition (MIT) in SrNbO 3 (SNO) thin films epitaxially grown on (110)-oriented DyScO 3 has been reported. SNO films are fabricated by the pulsed laser deposition technique at different partial O 2 pressure to vary the oxygen content and their structural, optical, and transport properties are probed. SNO unit cell has been found to shrink vertically as the oxygen content increases but keeping the epitaxial matching with the substrate. The results of Fourier-transform infra-red spectroscopy show that highly oxygenated SNO samples (i.e., grown at high oxygen pressure) show distinct optical conductivity behavior with respect to oxygen deficient films, hence demonstrating the insulating character of the formers with respect to those fabricated with lower pressure conditions. Tailoring the optical absorption and conductivity of strontium niobate epitaxial films across the MIT will favor novel applications of this material.

Fluorite Alumina Fuel Cells

“…This disruption ushers in localized states in the electronic density of states, leading to very different situations for the obtained uorite alumina materials with the emergence of insulating oxide phases. Indeed, oxygen-driven or disorder effects (Anderson type) metal-insulator transition are commonly observed in the literature 17,18 . Anyway, our theoretical calculating result gives us a meaningful vision and hints that distinctly different electronic states and band structures exist in the alumina uorite structure.…”