Strain-Induced Modulation of Resistive Switching Temperature in Epitaxial VO2 Thin Films on Flexible Synthetic Mica.

The resistive switching temperature associated with the metal-insulator transition (MIT) of epitaxial VO2 thin films grown on flexible synthetic mica was modulated by bending stress. The resistive switching temperature of polycrystalline VO2 and V2O5 thin films, initially grown on synthetic mica without a buffer layer, was observed not to shift with bending stress. By inserting a SnO2 buffer layer, epitaxial growth of the VO2 (010) thin film was achieved, and the MIT temperature was found to vary with the bending stress. Thus, it was revealed that the bending response of the VO2 thin film depends on the presence or absence of the SnO2 buffer layer. The bending stress applied a maximum in-plane tensile strain of 0.077%, resulting in a high-temperature shift of 2.3 °C during heating and 1.8 °C during cooling. After 104 bending cycles at a radius of curvature R = 10 mm, it was demonstrated that the epitaxial VO2 thin film exhibits resistive switching temperature associated with MIT.

Single-Domain and Atomically Flat Surface of κ-Ga2O3 Thin Films on FZ-Grown ε-GaFeO3 Substrates via Step-Flow Growth Mode.

Herein, single-domain κ-Ga2O3 thin films were grown on FZ-grown ε-GaFeO3 substrates via a step-flow growth mode. The ε-GaFeO3 possessing the same crystal structure and similar lattice parameters as those of the orthorhombic κ-Ga2O3 facilitated the growth of κ-Ga2O3 thin films, as observed by the X-ray diffraction (XRD) analysis. Furthermore, the surface morphologies of the κ-Ga2O3 thin films exhibited a step-terrace and atomically flat structure. XRD φ-scan and transmission electron microscopy with selected area electron diffraction revealed that there is no occurrence of in-plane rotational domains in the κ-Ga2O3 thin films on ε-GaFeO3 substrates and that the κ-Ga2O3 thin film comprised a single domain. TEM analysis revealed that there were no clear dislocations in the observation area. Moreover, high-resolution TEM observation showed that the atomic arrangements of the film and the substrate were continuous without the presence of an intermediate layer along the growth direction and were well-aligned in the in-plane direction.