Oxygen Vacancy Dynamics at Room Temperature in Oxide Heterostructures

Oxygen vacancy dynamic behavior at room temperature in complex oxides was carefully explored by using a combined approach of ion liquid gating technique and resistance measurements. Heterostructures of PrBaCo₂O_5+δ/Gd₂O₃-doped CeO₂ epitaxial thin films were fabricated on (001) Y₂O₃-stabilized ZrO₂ single crystal substrates for systematically investigating the oxygen redox dynamics. The oxygen dynamic changes as response to the gating voltage and duration were precisely detected by in situ resistance measurements. A reversible and nonvolatile resistive switching dynamics was detected at room temperature under the gating voltage >13.5 V with pulse duration >1 s

Oxygen Vacancy Dynamics at Room Temperature in Oxide Heterostructures

Oxygen vacancy dynamic behavior at room temperature in complex oxides was carefully explored by using a combined approach of ion liquid gating technique and resistance measurements. Heterostructures of PrBaCo₂O_5+δ/Gd₂O₃-doped CeO₂ epitaxial thin films were fabricated on (001) Y₂O₃-stabilized ZrO₂ single crystal substrates for systematically investigating the oxygen redox dynamics. The oxygen dynamic changes as response to the gating voltage and duration were precisely detected by in situ resistance measurements. A reversible and nonvolatile resistive switching dynamics was detected at room temperature under the gating voltage >13.5 V with pulse duration >1 s

Piezoelectric and Dielectric Properties of Multilayered BaTiO₃/(Ba,Ca)TiO₃/CaTiO₃ Thin Films

Highly oriented multilayered BaTiO₃–(Ba,Ca)­TiO₃–CaTiO₃ thin films were fabricated on Nb-doped (001) SrTiO₃ (Nb:STO) substrates by pulsed laser deposition. The configurations of multilayered BaTiO₃–(Ba,Ca)­TiO₃–CaTiO₃ thin films are designed with the thickness ratio of 1:1:1 and 2:1:1 and total thickness ∼300 nm. Microstructural characterization by X-ray diffraction indicates that the as-deposited thin films are highly <i>c</i>-axis oriented and large in-plane strain is determined in BaTiO₃ and CaTiO₃ layers. Piezoresponse force microscopy (PFM) studies reveal an intense in-plane polarization component, whereas the out-of-plane shows inferior phase contrast. The optimized combination is found to be the BaTiO₃–(Ba_0.85Ca_0.15)­TiO₃–CaTiO₃ structure with combination ratio 2:1:1, which displays the largest domain switching amplitude under DC electric field, the largest room-temperature dielectric constant ∼646, a small dielectric loss of 0.03, and the largest dielectric tunability of ∼50% at 400 kV/cm. These results suggest that the enhanced dielectric and tunability performance are greatly associated with the large in-plane polarization component and domain switching

Enhanced Metal–Insulator Transition Performance in Scalable Vanadium Dioxide Thin Films Prepared Using a Moisture-Assisted Chemical Solution Approach

Vanadium dioxide (VO₂) is a strong-correlated metal–oxide with a sharp metal–insulator transition (MIT) for a range of applications. However, synthesizing epitaxial VO₂ films with desired properties has been a challenge because of the difficulty in controlling the oxygen stoichiometry of VO_<i>x</i>, where <i>x</i> can be in the range of 1 < <i>x</i> < 2.5 and V has multiple valence states. Herein, a unique moisture-assisted chemical solution approach has been developed to successfully manipulate the oxygen stoichiometry, to significantly broaden the growth window, and to significantly enhance the MIT performance of VO₂ films. The obvious broadening of the growth window of stoichiometric VO₂ thin films, from 4 to 36 °C, is ascribed to a self-adjusted process for oxygen partial pressure at different temperatures by introducing moisture. A resistance change as large as 4 orders of magnitude has been achieved in VO₂ thin films with a sharp transition width of less than 1 °C. The much enhanced MIT properties can be attributed to the higher and more uniform oxygen stoichiometry. This technique is not only scientifically interesting but also technologically important for fabricating wafer-scaled VO₂ films with uniform properties for practical device applications