High-power impulse magnetron sputtering (HiPIMS) was used to deposit ITO/Ag/ITO (IAgI) and ITO/Cu/ITO (ICuI) sandwiched films on polyethylene naphthalate substrate at room temperature as flexible transparent conductive materials. The hybrid layers were constructed with 40 nm ITO bottom and top layers, and a 5–20 nm Ag or Cu interlayer. The microstructure and optoelectrical properties were estimated for these films with various thicknesses of the metal interlayer. Thanks to the high-power density and highly ionized plasma in the HiPIMS process, the IAgI and ICuI sandwich structures exhibited good crystallinity and smooth surfaces with high optical transmittance and low sheet resistance. The optimal figure of merit was obtained as 101.16 × 10⁻³·Ω⁻¹ for the IAgI film and 4.83 × 10⁻³·Ω⁻¹ for the ICuI film with the metal interlayer thickness of 10 nm, both of which are higher than that from a similar structure reported via sputtering at room temperature. These results indicate that HiPIMS is a promising technique to deposit transparent conductive films onto soft substrates for applications in flexible optoelectronic devices.

Gallium oxide (Ga₂O₃) thin films were fabricated on glass substrates using a combination of chemical bath deposition and post-annealing process. From the field-emission scanning electron microscopy and x-ray diffraction results, the GaOOH nanorods precursors with better crystallinity can be achieved under higher concentrations (≥0.05 M) of gallium nitrate (Ga(NO₃)₃). It was found that the GaOOH synthesized from lower Ga(NO₃)₃ concentration did not transform into α-Ga₂O₃ among the annealing temperatures used (400–600 °C). Under higher Ga(NO₃)₃ concentrations (≥0.05 M) with higher annealing temperatures (≥500 °C), the GaOOH can be transformed into the Ga₂O₃ film successfully. An α-Ga₂O₃ sample synthesized in a mixed solution of 0.075 M Ga(NO₃)₃ and 0.5 M hexamethylenetetramine exhibited optimum crystallinity after annealing at 500 °C, where the α-Ga₂O₃ nanostructure film showed the highest aspect ratio of 5.23. As a result, the photodegeneration efficiencies of the α-Ga₂O₃ film for the methylene blue aqueous solution can reach 90%.

In this study, the Pd/BiVO₄ composite was prepared by hydrothermal method as an electrochemical sensing material for epinephrine. X-ray diffraction, scanning electron microscopy, and a transmission electron microscope were used to characterize the samples. In the electrochemical detection system, cyclic voltammetry and differential pulse voltammetry were applied to measure the concentration of the epinephrine solution (0.9–27.5 µM) with the Pd/BiVO₄-coated glassy carbon electrode. As a result, the oxidation peak current of Pd/BiVO₄/GCE demonstrated good linearity with the epinephrine concentration. The detection limit of the epinephrine concentration by cyclic voltammetry and differential pulse voltammetry were 0.262 µM and 0.154 µM, respectively. Additionally, the proposed sensing material exhibited good reproducibility, stability, and selectivity. A plausible sensing mechanism was proposed.

The metal-semiconductor-metal photodetectors based on the sputtered gallium oxide films on sapphire substrates after various post-thermal treatments have been investigated. The photodetector performance of the furnace-annealed gallium oxide sample degraded with the increase of annealing temperature from 700 to 1000 ${\degree \text C}$ , resulting from the adverse effect of the aluminum cross-diffusion and polycrystalline formation. By rapid thermal annealing at 800 ${\degree \text C}$ , the gallium oxide film can achieve an optimum photodetector performance with the photo/dark current ratio of ${1.78 \times 10^{5}}$ (@ 5V and 230 nm), responsivity of 0.553 A/W, and fast transient response (rise/fall time: 0.2 s/0.1 s). The result is comprehensively better than the previous reports by sputtering, which demonstrates that the quasi-single-crystalline gallium oxide film via rapid thermal process has high potential for deep-ultraviolet photodetector applications.