Effect of Substrate Temperature on the Structural, Optical and Electrical Properties of DC Magnetron Sputtered VO₂ Thin Films

This study focuses on the effect of the substrate temperature (TS) on the quality of VO2 thin films prepared by DC magnetron sputtering. TS was varied from 350 to 600 °C and the effects on the surface morphology, microstructure, optical and electrical properties of the films were investigated. The results show that TS below 500 °C favors the growth of V2O5 phase, whereas higher TS (≥500 °C) facilitates the formation of the VO2 phase. Optical characterization of the as-prepared VO2 films displayed a reduced optical transmittance (T˜) across the near-infrared region (NIR), reduced phase transition temperature (Tt), and broadened hysteresis width (ΔH) through the phase transition region. In addition, a decline of the luminous modulation (ΔT˜lum) and solar modulation (ΔT˜sol) efficiencies of the as-prepared films have been determined. Furthermore, compared with the high-quality films reported previously, the electrical conductivity (σ) as a function of temperature (T) reveals reduced conductivity contrast (Δσ) between the insulating and metallic phases of the VO2 films, which was of the order of 2. These outcomes indicated the presence of defects and unrelaxed lattice strain in the films. Further, the comparison of present results with those in the literature from similar works show that the preparation of high-quality films at TS lower than 650 °C presents significant challenges

The Effect of Substrate Biasing during DC Magnetron Sputtering on the Quality of VO2 Thin Films and Their Insulator–Metal Transition Behavior

In this work, VO2 thin films were deposited on Si wafers (onto (100) surface) by DC magnetron sputtering under different cathode bias voltages. The effects of substrate biasing on the structural and optical properties were investigated. The results show that the metal–insulator transition (MIT) temperature of VO2 thin films can be increased up to 14 K by applying a cathode bias voltage, compared to deposition conditions without any bias. The decrease in the transition efficiency and increase in the transition temperature are attributed to the enlarged grain size, increased defects, and the residual stress in the VO2 thin films induced by biasing. The optical transmittance measurements for different thickness films indicate an attenuation coefficient of 3.1 × 107 m−1 at 2000 nm or an extinction coefficient of 4.9 in the metal phase. The optical transmittance vs wavelength characteristics point to an indirect bandgap of 0.6 ± 0.05 eV and significant scattering in the bulk and/or at the interface

Diagnostic Potential of Differentially Expressed Homer1 and Homer2 in Ischemic Stroke

Background: Ischemic stroke (IS) is an extremely heterogeneous disease with variable pathogenesis. Due to the lack of early diagnostic marker, the mortality rate of IS remains high worldwide. The family of Homer plays an important role in the pathology of atherosclerotic plaque. In this study, we have investigated its expression pattern and clinical significance in IS. Methods: RT-qPCR was performed to detect the expression of Homer1, Homer2, and Homer3. Results: We found that the mRNA levels of Homer1 (pConclusion: Our data suggested that Homer1 and Homer2 might be considered as novel diagnostic biomarkers for LAA stroke