Abstract
We report direct evidence that oxygen vacancies affect the structural and electrical parameters in tensile-strained NdNiO3−δ epitaxial thin films by elaborately adjusting the amount of oxygen deficiency (δ) with changing growth temperature TD. The modulation in tensile strain and TD tended to increase oxygen deficiency (δ) in NdNiO3−δ thin films; this process relieves tensile strain of the thin film by oxygen vacancy incorporation. The oxygen deficiency is directly correlated with unit-cell volume and the metal-insulator transition temperature (TMI), i.e., resulting in the increase of both unit-cell volume and metal-insulator transition temperature as oxygen vacancies are incorporated. Our study suggests that the intrinsic defect sensitively influences both structural and electronic properties, and provides useful knobs for tailoring correlation-induced properties in complex oxides.
Highlights
Correlated transition metal oxides with partially-filled d electrons undergo intriguing metal-insulator electronic phase transition (MIT)[1, 2] as a result of electron interactions[3]
Θ–2θ X-ray diffraction (XRD) symmetrical scan of NNO thin films on (001) LSAT (Fig. 1b) and STO (Fig. 1c) substrates grown at 500 ≤ TD ≤ 800 °C show a (002) NNO peak near the (002) substrate peak; this observation indicates that the NNO films grew epitaxially in the c-axis orientation regardless of the growth temperature (TD)
As TD increased from 500 °C, NNO peak was moved to slightly higher scattering angle until to 600 °C for NNO on LSAT, and until 650 °C on STO, shifted to the lower scattering angle as TD increased further
Summary
Correlated transition metal oxides with partially-filled d electrons undergo intriguing metal-insulator electronic phase transition (MIT)[1, 2] as a result of electron interactions[3]. To investigate the effect of pure oxygen vacancy on TMI in RNiO3 thin films, their effect must be isolated from other stimuli such as cation stoichiometry and strain states In this Article, we report systematic control of oxygen deficiency in NNO epitaxial thin films with in-plane tensile strain and investigate the influence of oxygen deficiency on the MIT characteristics. TMI was directly correlated with the unit-cell’s structural expansion, which is a direct measure of oxygen deficiency These results demonstrate the influence of TD on the formation of oxygen vacancies, and provide insights into the effect of oxygen deficiency on the correlated phase in rare-earth nickelates
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