6 research outputs found
High-Density Silicon Nanowires Prepared via a Two-Step Template Method
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
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
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
IronÂ(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
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