电子束蒸发法在多孔氧化铝膜上制备银纳米点阵列

采用二步阳极氧化法在草酸溶液中制备了高度有序的多孔阳极氧化铝(Porous Anodic Alumina,PAA)薄膜。以多孔氧化铝薄膜为模板,采用真空电子束蒸发的方法在多孔氧化铝模板上制备出了高度有序的金属银纳米点阵列体系。扫描电镜(SEM)测试结果表明,所制备的金属银纳米点阵列与多孔阳极氧化铝膜的多孔阵列具有完全相同的有序结构,阵列中银纳米颗粒的形状接近球形,其直径大约为70nm,与氧化铝模板的孔径基本一致。研究了高度有序银纳米点阵列的形成过程。     

高质量多孔氧化铝模板的制备

在草酸电解液中研究了阳极氧化法制备多孔氧化铝模板(AAO模板)。采用场发射扫描电子显微镜对多孔模板的形貌进行表征,结果表明:模板孔的分布均匀有序,孔径在40~70 nm;电解液浓度、氧化电压、氧化温度和氧化时间都会影响模板的形态;不经过高温退火及抛光也可以制得规则排布的多孔AAO模板。X射线衍射分析表明:氧化铝膜的主要成分为非晶态Al2O3。     

一种可控纳米柱阵列的研制

在一次阳极氧化法制备多孔氧化铝(anodized aluminum oxide,AAO)的基础上,进行了二次、三次、四次氧化制备AAO,并对多次氧化制备多孔AAO的电流变化曲线和模板表面的形貌特点等进行了比较分析.二次、三次、四次氧化制备的AAO纳米孔孔径依次增大、孔间距减小,而模板表面的纳米孔有序性分布没有明显变化.控制一次氧化AAO模板的除膜时间,～10 min即可得到孔径规则、高度有序的AAO膜.最后,利用所制备的不同孔深和孔径的AAO为模板,通过热纳米压印复制技术制备了长度和直径等性质可控的PMMA纳米柱阵列. 关键词： 纳米柱阵列 聚甲基丙烯酸甲酯 多孔氧化铝模板 多次氧化法     

基于多孔氧化铝和单原子沉积技术的颜色调控方法研究

本文通过建立多孔氧化铝(porous alumina,PA)的物理模型及理论分析,提出与发展了一种基于PA和单原子沉积(atomic layer deposition,ALD)技术的颜色调控新方法.以实验制备的PA样品为原型,对孔径相同、孔中心距相同但孔深不同的一系列PA模板进行了颜色调控的仿真,揭示了调控色随孔深变化的规律;通过控制在草酸溶液中的阳极氧化时间,实验制备出平均孔径40 nm、平均孔中心距100 nm、孔深分别为296 nm和373 nm的两个PA样品;之后采用ALD技术在它们表面均沉积一层 关键词： 多孔氧化铝 颜色调控 单原子沉积     

纳米压印多孔硅模板的研究

纳米压印模板通常采用极紫外光刻、聚焦离子束光刻和电子束光刻等传统光刻技术制备,成本较高.寻找一种简单、低成本的纳米压印模板制备方法以提升纳米压印光刻技术的应用成为研究的重点与难点.本文以多孔氧化铝为母模板,采用纳米压印光刻技术对纳米多孔硅模板的制备进行了研究.在硅基表面成功制备出纳米多孔阵列结构,孔间距为350—560 nm,孔径在170—480 nm,孔深为200 nm.在激发波长为514 nm时,拉曼光谱的测试结果表明,相对于单面抛光的硅片,纳米多孔结构的硅模板拉曼光强有了约12倍左右的提升,对提升硅基光电器件的应用具有重要的意义.最后,利用多孔硅模板作为纳米压印母模板,通过热压印技术,成功制备出了聚合物纳米柱软模板.     

氧化铝模板制备过程中酸性电解液对模板参数的影响

多孔阳极氧化铝模板表面分布有纳米级微孔,其尺寸可调、有序性高,并且制备工艺简单,价格低廉,是合成各种纳米材料的重要方法.本文详细讨论了制备过程中各种实验条件对氧化铝膜参数的影响;给出了制备各种孔径高质量氧化铝模板的最佳实验条件,并对多孔氧化铝模板的应用前景做出了展望.     

AAO/Ag NPs复合体系光吸收特性

利用时域有限差分法设计并分析了基于多孔氧化铝与纳米银颗粒的AAO/Ag NPs光吸收器模型,采用物理气相沉积方法制备了AAO/Ag NPs复合体系样品,表征并测试了不同实验参数下样品的光吸收特性.测试结果表明制备的AAO/Ag NPs复合体系样品在400～2 500nm波段的光吸收率高达98%,且高的光吸收率几乎不受银纳米颗粒氧化的影响.理论计算与测试分析表明多孔氧化铝孔内壁沉积的颗粒越多,沉积深度越深,沉积的银颗粒尺寸范围越大,光吸收率越高,而多孔结构有效降低了入射光的反射率,其表面的银膜有效降低了出射光的透射率.     

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.     

基于包络线法的多孔阳极氧化铝薄膜光学常数的计算

采用二步阳极氧化法在草酸溶液中制备了多孔阳极氧化铝(PAA)薄膜。借助于扫描电子显微镜(SEM)分析了多孔阳极氧化铝薄膜的微观形貌。结果发现,在其表面孔径为30~40nm的六边形孔洞分布均匀,且垂直于表面平行生长。依据PAA透射光谱的实验数据,采用极值包络线算法计算出了PAA薄膜的复折射率以及光学能隙等光学常数。通过分析吸收系数与入射光子能量之间的关系发现,PAA薄膜具有直接带隙半导体的电子结构特征,而且由理论计算得到的PAA的带隙能与其光致发光谱的峰位能是一致的。     

聚丙烯酰胺凝胶法制备大孔α-氧化铝及其发光性能研究

采用聚丙烯酰胺凝胶法制备了大孔α-氧化铝材料.利用X射线衍射仪、扫描电镜、荧光分光光度计表征了所制备的氧化铝样品.结果表明,在1150℃烧结温度下可获得高纯的α-氧化铝陶瓷材料,其形貌呈类电路板型(monolithic)大孔结构.荧光光谱测试分析发现,在228 nm波长的光激发下,其荧光光谱在300-400 nm范围内由两个主发射带组成,其峰值分别位于330 nm和365nm.基于实验结果,探讨了多孔氧化铝的形成机理和发光机制.     

Controllable fabrication of highly ordered thin AAO template on Si substrate for electrodeposition of nanostructures

In this work, simple fabrication of hexagonally highly ordered porous anodic aluminum oxide (AAO) of Al thin film (1 μm) on Si substrate is described using two-step anodization method for electrochemical synthesis of nanostructures. In this method, the templates were prepared under the controllable conditions of the parameters, which give rise to the possibility of highly ordered nanopore arrays with a well aspect ratio. Pore widening was then fulfilled in 5 wt% phosphoric acid solution at 25 °C. The pore diameter and spacing are proportional to the applied voltage, which is due to the mechanical stress associated with the volume expansion of the aluminum during the anodization according to the mechanical stress model. Pore-widening solution adjusted the pore diameter and thinned the AAO barrier layer at room temperature under the control of etching time. As an application, Cu nanorods arrays embedded in anodic alumina (AAO) template were fabricated by dc electrodeposition. The characterization of the AAO templates and the Cu nanorods produced was made by X-ray diffraction, field emission scanning microscope, energy dispersive X-ray spectroscopy and atomic force microscope (AFM). The images of AFM show that porous AAO template under constant voltage is 40 V which presents the optimum ordering.     

不同分枝结构多孔氧化铝膜的制备和光学特性

在阳极氧化铝的制备过程中,采用二次氧化方法,通过降低二次氧化过程中的电压,使之变为初始电压的1n,得到了具有n个分枝结构的纳米孔径的氧化铝膜.利用岛津UV3101分光光度计测试了样品的透射光谱与偏振光谱.结果表明,在可见和近红外波段,线型孔径结构的多孔铝膜比Y型和枝状结构的多孔铝膜具有更好的透射性能,在偏振性能方面也有优势,更适合作含金属微偏振器件的膜板材料.     

Microscale steps and micro-nano combined structures by anodizing aluminum

In this paper, we firstly present a novel microscale-step structure fabricated by anodizing aluminum in a mixture of 0.05-0.5 wt% NaCl (HCl), 2 wt% H₃PO₄ and 20 wt% ethanol under potentials of 1-40 V at room temperature. Then, we present two micro-nano combined structures by integrating the microsteps with nanopores through multi-step anodizations. The microstep-nanopore hierarchical structure was obtained by re-anodizing the sample in oxalic acid, and the regular nanopores can be realized on the microscale patterned aluminum surface. The two-layer porous structure was one layer of nanoporous anodic alumina and another layer of micropores by two-step anodization on sample's both sides. These two novel structures can be useful for surface engineering and high flux filtration, respectively. The current fabrication approach broadens the applications of aluminum anodization, and brings a new method for assembling micro-nano structures.     

The investigation of photoluminescence centers in porous alumina membranes

To investigate the origin of blue photoluminescence (PL) in porous alumina membrane, we have prepared an anodic aluminum oxide film with a pore diameter of 40 nm in oxalic acid solution by a two-step anodization process. Our results show that the as-prepared alumina membrane is amorphous and exhibits a broad emission band peaking at around 452 nm with two sub-peaks located at 443 nm and 470 nm. As indicated by the PL excitation spectra, there are two excitation peaks which can account for the sub-peaks observed in the PL emission band. We have proposed that the broad emission band with two sub-peaks can be attributed to two luminescence centers in porous alumina membranes, namely, oxygen defects and oxalic impurities. Furthermore, we have rationalized that the two emission centers show similar influence on the PL band in the blue region based on a simple model. PACS 81.07.-b; 81.16.Dn; 79.60.Jv     

Laser damage mechanism of porous Al2O3 films prepared by a two-step anodization method

Pure aluminum films were deposited on a B270 glass by electron beam evaporation technique. These aluminum films, which were used as anode, were put in sulfuric acid and oxalic acid to prepare porous alumina films using a two-step anodization method. The microstructure and laser damage characteristics of the alumina films were then tested. Results show that the microstructure of the alumina films formed in sulfuric acid and oxalic acid were vertical (cylindrical) pores with different diameters. The laser-damaged spot of the porous films was formed by innumerable small damaged pits with no mutual influence. Films prepared in different acids reveal different damage characteristics and reflect different mechanisms.     

EDLC characteristics with high specific capacitance of the CNT electrodes grown on nanoporous alumina templates

Well-ordered nanoporous alumina templates were fabricated by two-step anodization method by applying a constant voltage of 40 V in oxalic acid solution or of 25 V in sulfuric acid solution. The cylindrical pore diameter and pore density of the templates utilized for the carbon nanotube (CNT) growth were 86 ± 5 nm and 1.2 × 10¹⁰ cm⁻² in oxalic acid solution and 53 ± 1 nm and 3.1 × 10¹⁰ cm⁻² in sulfuric acid solution, respectively. The CNTs with uniform diameter of 50 ± 10 nm (oxalic acid) and 44 ± 2 nm (sulfuric acid) were grown on the porous alumina template as electrode materials for the electrochemical double layer capacitor (EDLC). The EDLC characteristics were examined by measuring the capacitances from cyclic voltammograms and the charge–discharge curves. The specific capacitances of the CNT electrodes are 30 ± 1 F/g (Φ = 50 ± 10 nm) and 121 ± 5 F/g (Φ = 44 ± 2 nm). The high specific capacitance of the CNT electrode was achieved by using nanoporous alumina templates with the high pore density and the small and uniform pore diameter.     

Laser-induced damage characteristic of porous alumina optical films

Pure aluminum films were deposited on B270 glass by electron beam evaporation technique. The aluminum films, which were used as anode, were placed in phosphoric acid to prepare porous alumina films using a two-step anodization method. They were subsequently annealed in high temperature to improve transmission. The microstructure, transmitted spectrum and laser damage characteristics of the alumina films were then tested. Their microstructure formed in phosphoric acid was retiform. The transmissivity can be increased efficiently if the annealing temperature is adequately high. The laser-damaged spots of the porous films were formed by innumerable small damaged pits with no mutual effect. In contrast, the laser-damaged spots of the compact films were formed by several larger damaged pits which acted together toward expansion. The damage process of the porous films comprised heat ablation and stress fracture.