6 research outputs found

    High-Density Silicon Nanowires Prepared via a Two-Step Template Method

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    High density ordered Si nanowire arrays can be fabricated from a Fe<sub>2</sub>O<sub>3</sub> template annealed from polystyrene (PS) microsphere layers via a metal-assisted chemical etching method. The metal mesh films, containing position- and density-defined pores that determine the position and density of the remaining structures after etching, are extremely important for achieving high quality Si nanowires. By adding a structural inversion process, a Au metal mesh with arrays of high density nanopores is devised as a catalyst for metal-assisted chemical etching of silicon. The density of Si nanowires can be increased to two times that of the single-layer PS microspheres and further to three times when a double layer of PS microspheres is introduced. The two-step template method for the preparation of high-density Si nanowires shows great potential in the fields of nanofabrication and nanoelectronics

    A New Route To Fabricate Large-Area, Compact Ag Metal Mesh Films with Ordered Pores

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    Ordered Si nanowire (SiNW) arrays can be fabricated by metal-assisted chemical etching. The metal mesh films (MMFs) are extremely important for achieving a high quality of the SiNWs. We have developed a two-step chemical deposition method to obtain compact porous Ag MMFs. By the separation of the nucleation and growth stages of the metal in the two-step deposition processes, the overgrowth of the metals to form randomly aggregated irregular metal particles can be overcome. Hexagonally arranged polystyrene (PS) latex microspheres have been employed as a template for the deposition of porous Ag MMFs. The spacing of the pores in the Ag MMFs is determined by the diameter of PS microspheres, and the pore size can also be tuned by changing Ar plasma etching time. One of the main advantages of the two-step deposition method lies in that Ag MMFs can be produced with PS microspheres that are not limited to a single layer, which dramatically simplifies the tedious processes of producing a monolayered PS template. The two-step chemical deposition method shows great potential in metal-assisted chemical etching

    Photocurrent Enhancement for Ti-Doped Fe<sub>2</sub>O<sub>3</sub> Thin Film Photoanodes by an In Situ Solid-State Reaction Method

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    In this work, a higher concentration of Ti ions are incorporated into hydrothermally grown Ti-doped (2.2% by atomic ratio) micro-nanostructured hematite films by an in situ solid-state reaction method. The doping concentration is improved from 2.2% to 19.7% after the in situ solid-state reaction. X-ray absorption analysis indicates the substitution of Fe ions by Ti ions, without the generation of Fe<sup>2+</sup> defects. Photoelectrochemical impedance spectroscopy reveals the dramatic improvement of the electrical conductivity of the hematite film after the in situ solid-state reaction. As a consequence, the photocurrent density increases 8-fold (from 0.15 mA/cm<sup>2</sup> to 1.2 mA/cm<sup>2</sup>), and it further increases up to ∼1.5 mA/cm<sup>2</sup> with the adsorption of Co ions. Our findings demonstrate that the in situ solid-state reaction is an effective method to increase the doping level of Ti ions in hematite films with the retention of the micro-nanostructure of the films and enhance the photocurrent

    Micro-Nano-Structured Fe<sub>2</sub>O<sub>3</sub>:Ti/ZnFe<sub>2</sub>O<sub>4</sub> Heterojunction Films for Water Oxidation

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    Iron­(III) oxide photoelectrodes show promise in water oxidation applications. In this study, micro-nano-structured hematite films are synthesized, and Ti ions are doped to improve photoelectric conversion efficiency. The photocurrent increases for enhanced electrical conductivity. Further enhanced photocurrent is achieved for Fe<sub>2</sub>O<sub>3</sub>:Ti/ZnFe<sub>2</sub>O<sub>4</sub> heterojunction electrodes. Cyclic voltammograms combined with optical absorbance examinations demonstrate that the conduction and valence band edges of ZnFe<sub>2</sub>O<sub>4</sub> shift from those of Ti doped Fe<sub>2</sub>O<sub>3</sub> to the negative direction, which facilitates the efficient separation of electron–hole pairs at the Fe<sub>2</sub>O<sub>3</sub>:Ti/ZnFe<sub>2</sub>O<sub>4</sub> interface. These findings demonstrate that, by doping hematite and by engineering the interface between the hematite and the electrolyte, charge separation can be effectively promoted and photocurrent density can be dramatically increased

    Silver Nanowire Transparent Conductive Films with High Uniformity Fabricated via a Dynamic Heating Method

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    The uniformity of the sheet resistance of transparent conductive films is one of the most important quality factors for touch panel applications. However, the uniformity of silver nanowire transparent conductive films is far inferior to that of indium-doped tin oxide (ITO). Herein, we report a dynamic heating method using infrared light to achieve silver nanowire transparent conductive films with high uniformity. This method can overcome the coffee ring effect during the drying process and suppress the aggregation of silver nanowires in the film. A nonuniformity factor of the sheet resistance of the as-prepared silver nanowire transparent conductive films could be as low as 6.7% at an average sheet resistance of 35 Ω/sq and a light transmittance of 95% (at 550 nm), comparable to that of high-quality ITO film in the market. In addition, a mechanical study shows that the sheet resistance of the films has little change after 5000 bending cycles, and the film could be used in touch panels for human–machine interactive input. The highly uniform and mechanically stable silver nanowire transparent conductive films meet the requirement for many significant applications and could play a key role in the display market in a near future
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