Efficient Hydrogen Evolution by Mechanically Strained MoS₂ Nanosheets

We demonstrated correlations between mechanically bent tensile-strain-induced two-dimensional MoS₂ nanosheets (NSs) and their electrochemical activities toward the hydrogen evolution reaction (HER). The tensile-strain-induced MoS₂ NSs showed significantly steeper polarization curves and lower Tafel slopes than the strain-free ones, which is consistent with the simple d-band model. Furthermore, the mechanical strain increased the electrochemical activities of all the NSs toward the HER except those loaded with high MoS₂ mass. Mechanically bending MoS₂ NSs to induce tensile strain enables the production of powerful, efficient electrocatalysis systems for evolving hydrogen

Low-Temperature, Solution-Processed ZrO₂:B Thin Film: A Bifunctional Inorganic/Organic Interfacial Glue for Flexible Thin-Film Transistors

A solution-processed boron-doped peroxo-zirconium oxide (ZrO₂:B) thin film has been found to have multifunctional characteristics, providing both hydrophobic surface modification and a chemical glue layer. Specifically, a ZrO₂:B thin film deposited on a hydrophobic layer becomes superhydrophilic following ultraviolet–ozone (UVO) treatment, whereas the same treatment has no effect on the hydrophobicity of the hydrophobic layer alone. Investigation of the ZrO₂:B/hydrophobic interface layer using angle-resolved X-ray photoelectron spectroscopy (AR XPS) confirmed it to be chemically bonded like glue. Using the multifunctional nature of the ZrO₂:B thin film, flexible amorphous indium oxide (In₂O₃) thin-film transistors (TFTs) were subsequently fabricated on a polyimide substrate along with a ZrO₂:B/poly-4-vinylphenol (PVP) dielectric. An aqueous In₂O₃ solution was successfully coated onto the ZrO₂:B/PVP dielectric, and the surface and chemical properties of the PVP and ZrO₂:B thin films were analyzed by contact angle measurement, atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The surface-engineered PVP dielectric was found to have a lower leakage current density (<i>J</i>_leak) of 4.38 × 10^–8 A/cm² at 1 MV/cm, with no breakdown behavior observed up to a bending radius of 5 mm. In contrast, the electrical characteristics of the flexible amorphous In₂O₃ TFT such as on/off current ratio (<i>I</i>_on/off) and electron mobility remained similar up to 10 mm of bending without degradation, with the device being nonactivated at a bending radius of 5 mm. These results suggest that ZrO₂:B thin films could be used for low-temperature, solution-processed surface-modified flexible devices

Adopting Novel Strategies in Achieving High-Performance Single-Layer Network Structured ZnO Nanorods Thin Film Transistors

High-performance, solution-processed transparent and flexible zinc oxide (ZnO) nanorods (NRs)-based single layer network structured thin film transistors (TFTs) were developed on polyethylene terephthalate (PET) substrate at 100 °C. Keeping the process-temperature under 100 °C, we have improved the device performance by introducing three low temperature-based techniques; regrowing ZnO to fill the void spaces in a single layer network of ZnO NRs, passivating the back channel with polymer, and adopting ZrO₂ as the high-<i>k</i> dielectric. Notably, high-<i>k</i> amorphous ZrO₂ was synthesized and deposited using a novel method at an unprecedented temperature of 100 °C. Using these methods, the TFTs exhibited a high mobility of 1.77 cm²/V·s. An insignificant reduction of 2.18% in mobility value after 3000 cycles of dynamic bending at a radius of curvature of 20 mm indicated the robust mechanical nature of the flexible ZnO NRs SLNS TFTs

Boron-Doped Peroxo-Zirconium Oxide Dielectric for High-Performance, Low-Temperature, Solution-Processed Indium Oxide Thin-Film Transistor

We developed a solution-processed indium oxide (In₂O₃) thin-film transistor (TFT) with a boron-doped peroxo-zirconium (ZrO₂:B) dielectric on silicon as well as polyimide substrate at 200 °C, using water as the solvent for the In₂O₃ precursor. The formation of In₂O₃ and ZrO₂:B films were intensively studied by thermogravimetric differential thermal analysis (TG-DTA), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FT IR), high-resolution X-ray diffraction (HR-XRD), and X-ray photoelectron spectroscopy (XPS). Boron was selected as a dopant to make a denser ZrO₂ film. The ZrO₂:B film effectively blocked the leakage current at 200 °C with high breakdown strength. To evaluate the ZrO₂:B film as a gate dielectric, we fabricated In₂O₃ TFTs on the ZrO₂:B dielectrics with silicon substrates and annealed the resulting samples at 200 and 250 °C. The resulting mobilities were 1.25 and 39.3 cm²/(V s), respectively. Finally, we realized a flexible In₂O₃ TFT with the ZrO₂:B dielectric on a polyimide substrate at 200 °C, and it successfully operated a switching device with a mobility of 4.01 cm²/(V s). Our results suggest that aqueous solution-processed In₂O₃ TFTs on ZrO₂:B dielectrics could potentially be used for low-cost, low-temperature, and high-performance flexible devices