虹彩环形结构色氧化铝薄膜的制备与研究

在草酸电解液中, 利用一次电化学氧化法成功的制备了孔洞深度和孔径由薄膜中心向外呈对称性递减的新型氧化铝薄膜, 且氧化铝薄膜呈现出虹彩环形结构色. 通过控制氧化电压和氧化时间可以调控虹彩环的疏密程度. 对草酸电解液中具有虹彩环形结构色氧化铝薄膜形成机理的理论分析表明, 在阳极电化学反应过程中, 阴极碳棒的作用效果类似点电极, 理论分析的结果与本文的实验现象相符合.     

Synthesis of highly ordered nanopores on a photoresist template for applications in nanofabrications

Template synthesis involves preparation of nanostructures of the desired material within the pores of a nanoporous membrane. In this paper we report on the fabrication of a new type of template, photoresist spin-coated on a conductive glass substrate, as an alternative to the commonly used track-etch polymeric membranes and anodic aluminium oxide. The nanopores on the photoresist are created by photolithography using a pre-designed pattern map stored in a Focused-Ion-Beam (FIB) machine. The pores created are highly ordered, of uniform and desired diameters of between 20–35 nm, and run the full length of the resist membrane. Pore dimensions are tenable in the range of 10 nm to hundreds nanometres in diameter and in the range of several micrometers in membrane thickness. We conclude that, in addition to being functionally similar to anodic alumina, the photoresist template is simpler and safer to fabricate making it a better alternative to in-house prepared anodic alumina templates and track-etch polymeric membranes.     

Optical properties and color generation mechanism of porous anodic alumina films

Porous anodic alumina thin films with iridescent colors were fabricated electrochemically in phosphoric acid electrolyte. Compared to the color saturation of alumina films fabricated in oxalic acid electrolyte, the saturation obtained using phosphoric acid was enhanced dramatically. The mechanisms behind this observation are discussed, and the microstructure and optical characteristics of the films are characterized. Multicolor patterns were obtained by an organics-assisted process for which details are given.     

Fabrication of Nanomaterials Using Porous Alumina Templates

Nanofabrication by self-organization methods has attracted much attention owing to the fact that it enables mass production without the use of expensive lithographical tools, such as an electron beam exposure system. Porous alumina can be fabricated electrochemically through anodic oxidation of aluminum by means of such a self-organization method, yielding highly ordered arrays of nanoholes several hundreds down to several tens of nanometers in size. This paper is an overview of recent research on porous alumina science and technology, nanohole array self-organization conditions and mechanisms, various methods of nanostructure formation using porous alumina templates, optical and magnetic nanofabrication, perspectives on electronic nano device fabrication and chemical/biological sensors and membranes.     

多孔氧化铝薄膜的制备和光学特性研究

采用阳极氧化法制备了二维有序纳米孔氧化铝膜.研究了工艺参数对多孔薄膜有序性、孔径、膜厚度等的影响，测量了多孔氧化铝有序膜的光透过、光吸收和光发射等光学特性.结果表明，在波长360 nm附近多孔氧化铝有序膜的光透过谱线和光吸收谱线发生突变，波长大于360 nm时，光透过增强；波长小于360 nm时，光吸收增强.多孔氧化铝有序膜的光致发光强度和峰位与激发光波长有关，光致发光谱范围在340~600 nm.     

Polarization properties of porous anodic alumina with Y-branched Cu nanowires

Porous anodic alumina (PAA) templates with branch structure are fabricated by the two-step anodic oxidation processes, and then the Y-branched Cu nanowires are synthesized in the templates using an alternating current (AC) deposition method. We observe the morphology image of the samples by scanning electron microscopy (SEM), and measure the transmission spectrum and the polarization spectrum of the samples by the spectrophotometer. The results show that PAA films with Y-branched Cu nanowires have better transmittance in the near infrared region. An extinction ratio of 15-18 dB and an insertion loss of 0.1-0.4 dB are obtained in this region. Therefore PAA with Y-branched Cu nanowires can be used as a near-infrared micropolarizer, and this kind of micropolarizer would have a promising future in the field of photoelectricity integration.     

含分枝铜纳米线多孔铝膜的偏振特性

利用二次阳极氧化法制备了具有分枝结构的多孔铝(PAA)模板,并以交流电化学沉积的方法在该模板中合成了分枝状的铜纳米线。用SEM观察样品的形貌结构,用分光光度计测量了样品的透射光谱和偏振光谱。实验结果表明,含分枝状铜纳米线结构的多孔铝膜在近红外光区具有较高的透射率,且得到了14～22 dB的消光比。这种微偏振器件制备方法简单、效率高、造价低,在光电集成领域有着广泛的应用前景。     

Bulge deformation measurement and elastic modulus analysis of nanoporous alumina membrane using time sequence speckle pattern interferometry

Nanoporous alumina membranes containing parallel regular pores of uniform size and normal to substrate surface were fabricated by anodically oxidizing high purity aluminum foils in acid solutions. The continuous out-of-plane displacement and current load of the porous membranes were obtained through bulge test combining time sequence speckle pattern interferometry (TSSPI) observation system. Then the deformation of whole field under different loads was deduced through point-to-point scan analysis and the elastic modulus was calculated through an analytical model. Measurement of mechanical properties indicates unusual mechanical behavior of these anodic alumina films compared with bulk alumina materials or dense alumina films. This method is useful and convenient for mechanical test on membranes with such structure and bring further understanding on connecting of micro–meso structure and mechanical properties.     

Alumina nanotubes and nanowires from Al-based porous alumina membranes

Using ultrasonic vibrations, we have successfully fabricated alumina nanotubes and nanowires from Al-based porous alumina membranes, which are the products of bulk aluminium in oxalic acid via electrochemical etching. Fine configurations and structures of the alumina nanotubes and nanowires are clearly revealed following a series of atomic force microscope and transmission electron microscope observations. Their formation mechanisms are analyzed in detail by comparing different growth characteristics of Al-based alumina membranes with Si-based alumina membranes. Based on our experimental results, we have also pointed out that when using porous alumina templates to fabricate nanostructured materials, it is necessary to carefully distinguish the obtained products from the alumina nanotubes and nanowires. PACS 82.45.Qr; 81.07.De     

FePt nano-stripes fabricated on anodic aluminum oxide templates

A new Fe Pt nanostructure with stripe-like patterns has been prepared by direct current(DC) magnetron sputtering on anodic aluminum oxide(AAO) templates. AAO templates anodized under low voltages(7 V) demonstrate self-organized,maze-like patterns, different from the conventional porous structures obtained at high voltages. Fe Pt thin films deposited on such templates tend to replicate the morphology of the templates. Although there is no obvious spatial ordering, the dimensions of the Fe Pt nano-stripes are highly uniform, due to the constrained growth along the transverse direction of the AAO pattern. The magnetic properties are strongly influenced by this unique morphology. While continuous films demonstrate strong exchange coupling, the dominant interaction in Fe Pt nano-stripes with the same nominal thickness is magnetostatic. The morphology also dictates the magnetization reversal behaviors, with thin films dominated by domain nucleation; while nano-stripes incline to reverse their magnetization by spin rotation. Our work demonstrates that selforganized AAO templates can be used to control the morphology and magnetic behavior of Fe Pt materials.     

Fabrication of segmented nanofibers by template wetting of multilayered alternating polymer thin films

Segmented polystyrene (PS) and poly-methyl methacrylate (PMMA) nanofibers were fabricated by wetting nanoporous alumina templates with multilayered polymer thin films. The order and thickness of the polymers within the thin films affected the resulting nanofiber morphology, PS and PMMA segment properties, and created unique core-shell structure in the PMMA segments. The core-shell structure suggests a complex wetting phenomenon. Fabrication of polymer nanostructures by wetting of layered thin films opens the arena of multifunctional, one-dimensional, polymer nanostructures with segments having individual and specific functionalities.     

Energy transfer in porous anodic alumina/rhodamine 110 nanocomposites

We have used porous anodic alumina (PAA) films as templates for embedding rhodamine 110 (Rh110) molecules and examined their photoluminescence (PL) properties in detail. The analysis of the polarization memory (PM) of PL strongly suggests that there is a significant energy transfer from PAA to Rh110 molecules. The effect of annealing the PAA layer on the PL properties of the nanocomposite has been studied. The results show that the energy transfer becomes more efficient in annealed PAA.     

Simple fabrication of hexagonally well-ordered AAO template on silicon substrate in two dimensions

In this study, thin anodic aluminum oxide (AAO) templates both on silicon substrates (AAO template/SiO₂/Si) and Ti-coated silicon substrates (AAO template/Ti/SiO₂/Si) were developed for design of magnetic, electronic and optoelectronic devices, chemical sensors and chip-scale lithium-ion rechargeable microbatteries. Two types of AAO template were prepared by using a two-step anodization procedure. The templates were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The obtained thin AAO templates were approximately 50 nm in diameter and 700 nm in length with 80-nm interpore distances in a relatively large area of 6 cm². A barrier layer of the AAO templates was removed by a cathodic polarization method in KCl solution for several seconds. The current–time transient during removing the alumina barrier layer of the thin AAO template and the mechanism of electrochemical dissolution of the barrier layer are given in detail.     

Organisation of carbon nanotubes and semiconductor nanowires using lateral alumina templates

Carbon nanotubes and semiconductor nanowires have been thoroughly studied for the future replacement of silicon-based complementary metal oxide semiconductor (CMOS) devices and circuits. However, the organisation of these nanomaterials in dense transistor arrays, where each device is capable of delivering drive currents comparable with those of their silicon counterparts is still a big challenge. Here, we present a novel approach to the organisation of carbon nanotubes and semiconductor nanowires, based on the use of porous lateral alumina templates obtained by the controlled anodic oxidation of aluminium thin films. We discuss the growth of nanomaterials inside the pores of such templates and show the feasibility of our approach. Our first results point to further work on controlling the synthesis of catalyst nanoparticles at the bottom of the pores, these particles being necessary to nucleate and sustain the growth of carbon nanotubes or semiconductor nanowires. To cite this article: D. Pribat et al., C. R. Physique 10 (2009).     

Use of photoresist templates in the synthesis of highly-ordered arrays of titania nanorods

Template synthesis of nanostructures entails the deposition of the desired materials within the pores of a nanoporous membrane or solid. Nanofibrils or tubules of the desired material are obtained within the pores depending on the deposition time and parameters. Methods such as electrochemical and electroless deposition, in situ polymerization, and sol–gel process have been used to deposit nanomaterials within the nanopores of templates such as track-etch polymeric membranes and anodic alumina. This paper reports on the first use of photoresist spin-coated on a conductive glass substrate as a template for nanofabrications. TiO₂ nanofibrils in diameters were synthesized by sol–gel process within the pores of the template. Removal of the template resulted in highly-ordered arrays of nanofibrils vertically standing on the conducting glass substrate. The aspect rations of the obtained nanofibrils were similar to those of the template nanopores, 35 nm in diameter and ∼1.3 microns in length. The photoresist template is shown to be functionally similar to anodic alumina template.     

Photoluminescence properties of heat-treated porous alumina films formed in oxalic acid

Photoluminescence and optical properties of as-anodized and heat-treated at 500 °C porous alumina films formed in a 0.3 M oxalic acid at 40 V have been studied. The FTIR indicates that the oxalate ions are embedded in the anodic alumina as chelating bidentate structures and further heating up to 500 °C does not cause any change in ion coordination. The results of time-resolved spectroscopy show the presence of two luminescence centers both in the as-anodized and heat-treated anodic alumina films with lifetimes of about 0.25 and 4.0 ns. The F⁺-centers in anodic alumina are responsible for the luminescence peak at about 420 nm, with a lifetime of about 4.0 ns. The luminescence peak at about 480 nm, with lifetime of about 0.25 ns, can be attributed to the luminescence of carboxylate ions existing in bulk of anodic alumina.     

Controlled synthesis of ZnO nanowires or nanotubes via sol-gel template process

ZnO nanowires and nanotubes have been rationally fabricated within the nanochannels of porous anodic alumina templates by an improved sol-gel template process. X-ray diffraction and selected area electronic diffraction demonstrate that the as-obtained ZnO nanowires and nanotubes can be indexed to hexagonal wurtzite polycrystalline. In this method, zinc nitrate and urea are used as precursors, zinc nitrate serve as zinc ions source, and urea offered a basic medium through its hydrolysis. ZnO nanowires or ZnO nanotubes can be obtained easily by controlling hydrolysis time. The formation mechanism of ZnO nanowires and nanotubes was also discussed.     

Electrochemical fabrication of arrayed alumina nanowires showing strong blue emission

Arrayed alumina nanowires having controlled uniform diameters of 30–90 nm and lengths of 2–10 μm have been fabricated electrochemically with a high yield using two-step anodized aluminum oxide membranes as templates. The observed photoluminescence of the arrayed alumina nanowires arising from the emission of F⁺ and F centers is strong and blue-shifted compared with that of porous alumina membranes due to the structural difference of Al₂O₃. Our synthesized alumina nanowires are also found to be chemically more stable than the templates.     

多孔阳极氧化铝膜的制备及其在一维纳米材料合成中的应用

从一维纳米材料的研究范畴入手 ,综述了多孔阳极氧化铝膜的结构特征、形成机理以及作为模板在合成纳米导电聚合物、纳米金属、纳米半导体、纳米复合材料及碳纳米管等方面的研究与应用的最新进展 ,揭示了多孔阳极氧化铝模板在合成与组装纳米新材料方面的重要作用 .     

<Emphasis Type="Italic">Para</Emphasis>-hexaphenyl nanofiber growth on Au-coated porous alumina templates

The availability of easy and reproducible methods for formation of periodically nanostructured surfaces allows one to study the quasi-epitaxial growth of nanowires on such artificially modified substrates. Here, we demonstrate that crystalline nanofibers of para-hexaphenyl can grow on porous alumina templates with high pore regularity once the templates have been coated by a thin Au film. Nanofibers of that kind represent a model system for the general class of organic nanowires which have chemically changeable optoelectronic properties and hence are of interest for integration into future optoelectronic devices.