Room-temperature oxygen vacancy migration induced reversible phase transformation during the anelastic deformation in CuO

From the mechanical perspectives, the influence of point defects is generally considered at high temperature, especially when the creep deformation dominates. Here, we show the stress-induced reversible oxygen vacancy migration in CuO nanowires at room temperature, causing the unanticipated anelastic deformation. The anelastic strain is associated with the nucleation of oxygen-deficient CuOx phase, which gradually transforms back to CuO after stress releasing, leading to the gradual recovery of the nanowire shape. Detailed analysis reveals an oxygen deficient metastable CuOx phase that has been overlooked in the literatures. Both theoretical and experimental investigations faithfully predict the oxygen vacancy diffusion pathways in CuO. Our finding facilitates a better understanding of the complicated mechanical behaviors in materials, which could also be relevant across multiple scientific disciplines, such as high-temperature superconductivity and solid-state chemistry in Cu-O compounds, etc.

Mechanistic insight into oxygen vacancy migration in SrFeO3–δ from DFT+U simulations

SrFeO3–δ is known to be an effective oxygen ion conductor and oxygen vacancies are central to its performance. SrFeO3–δ displays four crystallographic structural transitions as it undergoes oxygen reduction over...

Metal–insulator transition tuned by oxygen vacancy migration across TiO2/VO2 interface

Oxygen defects are essential building blocks for designing functional oxides with remarkable properties, ranging from electrical and ionic conductivity to magnetism and ferroelectricity. Oxygen defects, despite being spatially localized, can profoundly alter global properties such as the crystal symmetry and electronic structure, thereby enabling emergent phenomena. In this work, we achieved tunable metal–insulator transitions (MIT) in oxide heterostructures by inducing interfacial oxygen vacancy migration. We chose the non-stoichiometric VO2-δ as a model system due to its near room temperature MIT temperature. We found that depositing a TiO2 capping layer on an epitaxial VO2 thin film can effectively reduce the resistance of the insulating phase in VO2, yielding a significantly reduced ROFF/RON ratio. We systematically studied the TiO2/VO2 heterostructures by structural and transport measurements, X-ray photoelectron spectroscopy, and ab initio calculations and found that oxygen vacancy migration from TiO2 to VO2 is responsible for the suppression of the MIT. Our findings underscore the importance of the interfacial oxygen vacancy migration and redistribution in controlling the electronic structure and emergent functionality of the heterostructure, thereby providing a new approach to designing oxide heterostructures for novel ionotronics and neuromorphic-computing devices.