Song-Zhu Chu

Formation and Microstructures of Anodic Alumina Films from Aluminum Sputtered on Glass Substrate

A transparent porous alumina nanostructure was formed on a glass covered tin-doped indium oxide ~ITO! substrate by anodization of a highly pure sputtered aluminum layer. Details of the fabrication and microstructures of porous anodic alumina films are described and a possible mechanism of anodization is outlined. The variation of anodic current density reflects three processes, i.e., ~i! anodization of the sputtered aluminum layer, ~ii! transition of electrolysis from aluminum to the underlying ITO film, and~iii! electrochemical reactions on the ITO film beneath the anodic alumina film. As all the aluminum is completely anodized, the resultant oxide films on the ITO/glass substrate possess a parallel porous structure ~f80-100 nm, cell size in ;350 nm! with a thin arched barrier layer ~;80 nm! and exhibit a high transmittance in the ultraviolet-visible light range ~75-100% transmittance 300-900 nm!.

Large-Scale Fabrication of Ordered Nanoporous Alumina Films with Arbitrary Pore Intervals by Critical-Potential Anodization

Various ordered nanoporous alumina films with arbitrary pore intervals from 130 to 980 nm were fabricated on aluminum by a critical-potential anodization approach with sulfuric, phosphoric, oxalic, glycolic, tartaric, malic, and citric acid electrolytes under 70-450 V. The pore intervals of the porous alumina films were linearly proportional to applied potentials, with corresponding dominated territories to the electrolytes. In addition to pore interval, the self-ordering extent of pore arrangement was also improved with increasing anodizing potentials, leading to highly ordered porous alumina films at critical-high potentials. A cell separation phenomenon occurred for the films formed in sulfuric and glycolic acid solutions at the critical potentials, thus leading to the formation of highly ordered alumina nanotubule arrays. The critical-potential anodization in the other electrolytes produced self-organized porous alumina films with two-layered pore walls and pore bases. The basic principle for achieving porous alumina films with desired pore intervals is controlling the balance of the growth of barrier layer and the pore generation by adjusting the acidity, the concentration, and temperature of electrolytes. The porous alumina films formed in various electrolytes were transparent, and the transmittances of the films were inversely proportional to the applied potentials or the pore intervals.

Highly Porous (TiO2-SiO2-TeO2)/Al2O3/TiO2 Composite Nanostructures on Glass with Enhanced Photocatalysis Fabricated by Anodization and Sol-Gel Process.

Three-dimensional highly porous TiO2-4%SiO2-1%TeO2/Al2O3/TiO2 composite nanostructures (φ30-120 nm) directly fixed on glass substrates were fabricated by anodization of a superimposed Al/Ti layer sputter-deposited on glass and a sol-gel process. The porous composite nanostructures exhibited enhanced photocatalytic performances in decomposing acetaldehyde gas under UV illumination, which can be mainly ascribed to the combination of their large surface areas (7750-14770 m(2)/m(2)), high porosities (34.2-45.6%), and transparency. Specially, the composite nanostructure with ∼φ120 nm pores calcined at 500 °C showed the highest photocatalytic activity that is 6-10 times higher than commercial P-25 TiO2 under the experimental conditions.

Fabrication and characteristics of nanostructures on glass by Al anodization and electrodeposition

An ovel fabrication process of metal and semiconductor nanostructure arrays directly onto glass substrates is described below. An aluminum film was sputter-deposited on a glass substrate coated with a tin-doped indium oxide (ITO) film. The film was then anodically oxidized to obtain a porous alumina template with pore diameters ranging from 5 to 120 nm. Through appropriate chemical dissolution, the barrier layer of the anodic alumina film was removed and the underlying ITO film was exposed to the electrolytes, thus making it possible to deposit metals or semiconductors in the pores of anodic alumina films by a direct current (dc) electrodeposition. In Ni electrodeposition, the porous alumina films not only define the dimensions of the Ni nanowires but also influence their crystalline orientation, showing a textured {220} orientation for f 18 nm nanowires. In addition, through a cathodic electrosynthesis, a peroxocompound of titanium and ruthenium was deposited in the pores of anodic alumina film on ITO/glass substrate. After heating at 873 K for 2 h, a translucent TiO2/RuO2/Al2O3 composite nanostructure on the ITO/glass substrate was finally fabricated. # 2003 Elsevier Ltd. All rights reserved.

Highly porous TiO2/Al2O3 composite nanostructures on glass by anodization and the sol–gel process: fabrication and photocatalytic characteristics

Three-dimensional highly porous TiO2(–4%SiO2–1%TeO2)/Al2O3 composite nanostructures directly fixed on glass substrates are fabricated by anodization of a superimposed Al/Ti layer sputter-deposited on glass and a sol–gel process. The porous composite nanostructures (O 30–120 nm), with a surface layer containing anatase TiO2 with a preferential {004} reflection, possess large surface areas and exhibit an enhanced photocatalytic performance. In particular, the porous TiO2–4%SiO2–1%TeO2/Al2O3 composite nanostructure with O ∼ 120 nm pores shows the highest photocatalytic activity (quantum yield) and is 6 times higher than the commercial Degussa P-25 TiO2 powder under the experimental conditions.

New roots to formation of nanostructures on glass surface through anodic oxidation of sputtered aluminum

Abstract New processes for the preparation of nanostructure on glass surfaces have been developed through anodic oxidation of sputtered aluminum. Aluminum thin film sputtered on a tin doped indium oxide (ITO) thin film on a glass surface was converted into alumina by anodic oxidation. The anodic alumina gave nanometer size pore array standing vertically on the glass surface. Kinds of acids used in the anodic oxidation changed the pore size drastically. The employment of phosphoric acid solution gave several tens nanometer size pores. Oxalic acid cases produced a few tens nanometer size pores and sulfuric acid solution provided a few nanometer size pores. The number of pores in a unit area could be changed with varying the applied voltage in the anodization and the pore sizes could be increased by phosphoric acid etching. The specimen consisting of a glass substrate with the alumina nanostructures on the surface could transmit UV and visible light. An etched specimen was dipped in a TiO2 sol solution, resulting in the impregnation of TiO2 sol into the pores of alumina layer. The TiO2 sol was heated at ~400 °C for 2 h, converting into anatase phase TiO2. The specimens possessing TiO2 film on the pore wall were transparent to the light in UV–Visible region. The electro deposition technique was applied to the introduction of Ni metal into pores, giving Ni nanorod array on theglass surface. The removal of the barrier layer alumina at the bottom of the pores was necessary to attain smooth electro deposition of Ni. The photo catalytic function of the specimens possessing TiO2 nanotube array was investigatedin the decomposition of acetaldehyde gas under the irradiation of UV light, showing that the rate of the decomposition was quite large.

Fabrication of oxide nanostructures on glass by aluminum anodization and sol-gel process

Abstract A novel process of fabricating various oxide nanostructures on glass substrates is described. Transparent porous alumina films (∅ 6–150 nm) were first formed in acid solutions by anodization of aluminum layers sputter-deposited on a glass plate coated with a tin-doped indium oxide film. The porous alumina structures after pore-widened were then used as a host or a template in a sol–gel process to synthesize hollow or solid titania nanostructures within the nanopores, depending on the pore size of films and the affinity of the TiO 2 gel to alumina films. Finally, titania nanotubules (∼∅ 200 nm) or nanofibers (∼∅ 50 nm) arrays on glass were fabricated after the anodic alumina films were selectively removed.

Fabrication of TiO2 ­ Ru ( O 2 ) / Al2 O 3 Composite Nanostructures on Glass by Al Anodization and Electrodeposition

A novel process of fabricating transparent TiO 2 -RuO 2 /Al 2 O 3 composite nanostructures on indium tin oxide (ITO)-deposited glass substrate is described. Porous alumina films with pore diameters ranging from 5 to 120 nm were first formed by anodization of aluminum layers that were sputter-deposited on glass substrates coated with a tin-doped indium oxide (ITO) film. After removing the insulative barrier layer by a chemical dissolution, the porous alumina nanostructures on ITO/glass were then used as template electrodes in a cathodic electrosynthesis to deposit titania-ruthenium compounds within the nanopores. The X-ray photoelectron spectroscopy analytic results showed that titanium and ruthenium elements in the as-electrodeposited specimens exist in oxidation (IV) and metal state, respectively. The ruthenium worked as the conducting component that enables continuous electrodeposition of titania-based deposits with high electrical resistance. After heating at 873 K for 2 h, transparent composite nanostructures with TiO 2 -RuO 2 nanofibers (Φ20 ∼ 180 nm) embedded in alumina films on the ITO/glass substrate were finally achieved.

Fabrication and Characterization of Integrated Ultrahigh-Density Fe-Pt Alloy Nanowire Arrays on Glass

A method is reported for the fabrication of Fe-Pt binary alloy nanowire arrays embedded in porous alumina films with controlled diameters and high aspect ratios directly on glass substrates by successive anodization and cathodic electrodeposition in a novel bath with a simple composition. Porous alumina films with different pore sizes were initially formed by anodizing aluminum layers sputter-deposited on glass substrates covered with an indium tin oxide (ITO) film. After the insulative barrier layer was removed through a chemical dissolution, the porous alumina nanostructures on ITO/glass were used as template electrodes in dc electrodeposition to deposit Fe-Pt alloy within the nanopores, leading to integrated Fe-Pt nanowire (Φ23-52 nm) arrays on glass with high densities of 1.92-7.85 × 10 1 4 wire per square meter. The as-deposited Fe-Pt nanowires are composed of polycrystalline tetragonal FePt phase with crystal sizes 2-6 nm across. Thermal annealing at 973 K induced the crystal growth of disordered tetragonal FePt phase with appearance of (001) facet and developed the preferential magnetic orientation and enhanced coercivity in perpendicular direction (along the nanowire axis).

Direct Growth of Highly Ordered Crystalline Zirconia Nanowire Arrays with High Aspect Ratios on Glass by a Tailored Anodization

We report a facile approach to fabricate highly ordered zirconia nanowire arrays with controllable dimensions of φ25-40 nm in diameter, 100—550 nm in length, and 3-20 in aspect ratio by a tailored two-step anodization from superimposed At/Zr layers sputter-deposited on glass substrates. A porous-type Al anodization in a constant potential mode was performed on the Al layer on Zr/ glass in strong acidic electrolytes to form highly ordered porous alumina films with different pore sizes and intervals. Successively, a barrier-type Zr anodization in a constant current mode, at a low-critical-current density of 2 A m -2 with open potentials up to 70-500 V in different acidic electrolytes, was carried out on the underlying Zr film via the overlying PAA films, thereby allowing direct growth of the zirconia nanowires within the alumina nanopores on glass. The as-anodized zirconia nanowires were crystalline, comprising a mixture of monoclinic and orthorhombic ZrO 2 . In particular, the orthorhombic phase in the zirconia nanowires becomes more predominant with increasing terminal anodizing potentials and exhibits a preferential crystalline orientation in the (002) facet. The formation of anodic zirconia nanowires could be ascribed to the enhancement of the transport number of Zr cations in crystalline zirconia affected by the low-critical-current density and the impurities in the initial Zr film.