基于微纳结构与金属纳米层的颜色调控技术研究

本文提出一种基于微纳结构及金属纳米层的颜色调控方法. 通过理论分析研究, 建立了基于多孔氧化铝(PA) 微纳结构与金属纳米层的颜色调控物理模型. 以此为基础, 在孔深分别为250 nm和410 nm的PA模板表面磁控溅射铝(Al)金属纳米层, 对其反射干涉光谱分析可知, 通过控制PA模板的孔深可实现可见光谱范围内的颜色调控. 此外, 基于掩膜在孔深为410 nm的PA模板表面局域溅射铬(Cr)金属纳米层, 通过对其反射干涉光谱分析并与相同孔深的镀Al金属纳米层的PA颜色进行对比, 可以发现改变金属纳米层的材料和厚度同样可以实现颜色调控, 并通过局域颜色调控制备出彩色图案. 研究结果表明, 基于微纳结构及金属纳米层的颜色调控是一种切实可行和有效的方法.     

高质量规则多孔氧化铝模板的制备

在合适的条件下利用阳极氧化高纯铝片，可以获得多孔结构的氧化铝，其孔径大小和排列方式都很均匀.由于孔的深度不受限制，因此可以制备出孔深很大的多孔氧化铝.这种多孔结构可以用作制备纳米材料的模板.利用0.3mol/L的草酸溶液在40V的直流电压下，采用二步氧化法获得了高质量的氧化铝多孔模板，其典型孔径值为40—70nm，孔间距约110nm，深度可达毫米量级.分析了溶液温度对结果的影响，比较了单步法和两步法获得的样品的多孔结构，认为低温下的二步氧化法可以获得很好的多孔氧化铝模板. 关键词： 纳米材料 多孔氧化铝 二步氧化法     

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     

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.     

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.     

Co纳米孔洞模板的制备和磁性

利用纯度为995%的Al片进行阳极氧化,制成多孔氧化铝,通过两步纳米复合,制备了金属Co纳米孔洞模板.分别用透射电子显微镜(TEM)、X射线衍射仪(XRD)和振动样品磁强计(VSM)对样品进行了测试分析TEM观察的结果显示,模板孔洞分布均匀、局域有序,平均孔径为30nm左右,孔心距约为59nm;XRD测试的结果表明,模板是Co的多晶,并且具有明显的(002)取向;VSM测得模板的矫顽力为6164×104Am,比Co的块材有很大提高 关键词： 纳米孔洞模板 电化学 矫顽力     

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.     

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.     

基于原子层沉积技术的石英管表面减反射膜的制备

采用原子层沉积(ALD)技术在石英管表面制备了薄膜,研究了该薄膜的均匀性,以及石英管的内径、外径、长度对沉积薄膜均匀性的影响。以单波长减反射膜为研究对象,实验测试的反射光谱与仿真结果一致,石英管表面最低反射率可降至0.17%。忽略夹具影响,石英管外壁与内壁的减反射薄膜的非均匀性基本一致,在±1.69%范围内,内外壁表面减反射薄膜的厚度和中心波长相同,且石英管尺寸对内外壁薄膜均匀性无明显影响。利用ALD技术可在大曲率元件的内外表面沉积厚度偏差小且均匀性分布相似的减反射薄膜。     

染料敏化太阳能电池二氧化锡光阳极表面原子层沉积氧化铝研究

染料敏化薄膜太阳能电池作为一种新型的太阳能电池吸引了世界范围内的研究。采用二氧化锡代替传统的二氧化钛作为染料敏化太阳能电池的光阳极,使用含有I-/I-3氧化还原电解对的液态电解质。同时,通过原子层沉积(ALD)法,在150℃下使用三甲基铝(TMA)和水作为前驱体和氧化剂沉积氧化铝。并研究了ALD超薄氧化铝包覆二氧化锡颗粒对染料敏化太阳能电池光电转换效率的影响。椭圆偏振仪(SE)分析结果表明ALD每周期沉积速率约为1.2。X射线衍射(XRD)和场发射扫描电镜(FESEM)的结果表明,超薄氧化铝包覆没有影响多孔二氧化锡纳米晶薄膜的晶体结构和表面形貌。紫外-可见光谱(UV-Vis)研究发现随着氧化铝的沉积周期数增加,染料敏化电池光阳极吸附染料的能力增加。最后,对ALD氧化铝对染料敏化太阳能电池性能的影响机理进行了探讨。     

Optical and electrical properties of nanostructured implanted silicon n+-p junction passivated by atomic layer deposited Al2O3

This paper investigates the optical and electrical properties of nanostructured implanted silicon junctions passivated by Al₂O₃ layers. A two-step ion implantation method has been developed to fabricate the nanostructured n⁺-p junctions with theoretical support of two dimensional Monte Carlo simulations to predict and optimize the junction profile. Dense and uniform arrays of silicon nanopillars and nanocones were formed by combining nanosphere lithography and dry etching, exhibiting a low reflectance in a broad spectrum from 300 to 800 nm. A conformal Al₂O₃ layer was deposited on the array by using thermal atomic layer deposition (ALD) to achieve chemical passivation effect. External quantum efficiency and power conversion efficiency of the junctions were measured versus nanostructuration and Al₂O₃ passivation. The results showed that significant enhancement of efficiency can be achieved on the passivated nanopillar-based junctions.     

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.     

Plasmonic enhancement of blue emission from ZnO nanorods grown on the anodic aluminum oxide (AAO) template

Luminescent properties of ZnO nanorods covered with Ag nanoparticles are examined. Nanorods were synthesized on AAO templates using Atomic Layer Deposition (ALD) technique. Two types of the samples were prepared with different arrangement of ZnO nanorods and doping conditions. Nanorods of the second type were codoped with Al, to stimulate defect-related emissions. The ZnO material fills heterogeneously the interior of the AAO nanopores and has hexagonal, wurtzite structure. Both types of structures exhibit a broad defect-related emission at about 440 nm, most probably related to recombination at zinc interstitial (Zn_i) defects. This emission in samples with a random distribution of ZnO:Al nanorods and finer Ag nanoparticles is enhanced by factor of ～2.5 upon Ag deposition. The so-obtained material is interesting from the point of view of its application in blue range emitting diodes.     

The effect of iridium precursor on oxide-supported iridium catalysts prepared by atomic layer deposition

Alumina, silica and beta zeolite supported iridium catalysts were prepared by atomic layer deposition (ALD) from two different metal precursors, Ir(acac)₃ and Ir(thd)(COD). The use of Ir(thd)(COD) in ALD is reported for the first time. The aim was to investigate the effect of the precursor on catalyst surface species, chemical state and characteristics.Controllable ALD reaction was successful with both iridium precursors on alumina and with Ir(acac)₃ on β zeolite. On these catalysts, iridium particle sizes were very small (1-3 nm). Instead, some thermal decomposition of both precursors was observed during deposition on silica. At conditions, where no or very little decomposition of the precursors took place, the differences in the chemical state and characteristics of the as-prepared Ir/support samples were negligible, In ALD, Ir(acac)₃ is slightly more stable at high deposition temperatures (>200 °C) while Ir(thd)(COD) enables the utilization of larger temperature range since it vaporizes at lower temperature compared to Ir(acac)₃. The results thus indicate that Ir(thd)(COD) is a suitable new precursor for ALD.     

Characterization and electrical properties of high-<Emphasis Type="Italic">k</Emphasis> GdScO<Subscript>3</Subscript> thin films grown by atomic layer deposition

Gadolinium scandium oxide (Gd-scandate, GdScO₃) thin films were grown by atomic layer deposition (ALD) from β-diketonate precursors M(thd)₃ (M=Gd, Sc; thd=2,2,6,6-tetramethyl-3,5-heptanedionato) and ozone. The deposition parameters were optimized to produce films with the stoichiometric 1:1 metal ratio and a series of samples with nominal thicknesses of 5, 10, 15, and 20 nm were prepared. At 300 °C the metal precursor pulsing ratio Gd:Sc=5:6 yielded amorphous stoichiometric films and a growth rate of 0.21 Å/cycle. The films stayed amorphous up to 900 °C. The surface was probed with an AFM and the rms roughness was found to be 0.3 nm for the 5–20 nm thick films. The electrical properties of the as-deposited films proved to be very promising, with a dielectric constant of ～22 and leakage current density of 340 μA/cm², measured at -2 V.     

Enhanced rear‐side reflection and firing‐stable surface passivation of silicon solar cells with capping polymer films

Low refractive index polymer materials have been investigated with a view to form the back surface mirror of advanced silicon solar cells. SiO_x:H or AlO_y SiO_x:H polymer films were spun on top of an ultra‐thin (<10 nm) atomic‐layer‐deposited (ALD) Al₂O₃ layer, itself deposited on low‐resistivity (1 Ω cm) p‐type crystalline silicon wafers. These double‐layer stacks were compared to both ALD Al₂O₃ single layers and ALD Al₂O₃/plasma‐enhanced chemical vapour deposited (PECVD) SiN_x stacks, in terms of surface passivation, firing stability and rear‐side reflection. Very low surface recombination velocity (SRV) values approaching 3 cm/s were achieved with ALD Al₂O₃ layers in the 4–8 nm range. Whilst the surface passivation of the single ALD Al₂O₃ layer is maintained after a standard firing step typical of screen printing metallisation, a harsher firing regime revealed an enhanced thermal stability of the ALD Al₂O₃/SiO_x:H and ALD Al₂O₃/AlO_y SiO_x:H stacks. Using simple two‐dimensional optical modelling of rear‐side reflection it is shown that the low refractive index exhibited by SiO_x:H and AlO_y SiO_x:H results in superior optical performance as compared to PECVD SiN_x, with gains in photogenerated current of ～0.125 mA/cm² at a capping thickness of 100 nm. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Large scale synthesis of pinhole‐free shell‐isolated nanoparticles (SHINs) using improved atomic layer deposition (ALD) method for practical applications

Shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) as a new member of Raman technique garnered great attention among scientific community. In this work, we used an improved experimental setup to float the bare silver nanoparticles in air with the help of extraneous airflow, and used atomic layer deposition (ALD) method to coat ultra‐thin inert shell without pinholes. Under optimal conditions, we successfully prepared three kinds of SHINERS NPs (Ag@Al₂O₃, Ag@SiO₂ and Ag@TiO₂) in large quantity without pinholes. The ultra‐thin inert shell maintains the SERS activity of silver nanoparticles for long period of time. Transmission electron microscopy (TEM) images confirm the uniform coating of shell material on silver nanoparticles. Finally, the as‐prepared SHINs have been applied to detect various samples to demonstrate the applications. The presented ALD method offers a unique way to coat ultrathin shell (1–10 nm) on metal nanoparticles in large quantity (1–10 g) for practical applications. Copyright © 2015 John Wiley & Sons, Ltd.     

The influence of surface roughness in X-ray resonant magnetic reflectivity experiments

We present simulations of X-ray resonant magnetic reflectivity (XRMR) spectra of the surface magnetic dead layer in La_1−x Sr _x MnO₃ (LSMO) films that take in account the effect of different forms of roughness that can be encountered experimentally. The results demonstrate a method to distinguish between surface (morphological) roughness, and two generic kinds of magnetic roughness at the buried interface between the surface dead layer and the fully magnetic bulk part of the film. We show that the XRMR technique can distinguish between different types of magnetic roughness at the dead layer/bulk interface only if the sample surface is nearly atomically flat (the morphological roughness is one unit cell or less). Furthermore, to distinguish between the two types of magnetic roughness, the simulations show that fitting of XRMR spectra out to very high incidence angles must be performed. In the specific case of LSMO films with a dead layer with average thickness of 4 unit cells, this corresponds to an incidence angle > 50^∘.     

Silicon solar cells with Al2O3 antireflection coating

The paper presents the possibility of using Al₂O₃ antireflection coatings deposited by atomic layer deposition ALD. The ALD method is based on alternate pulsing of the precursor gases and vapors onto the substrate surface and then chemisorption or surface reaction of the precursors. The reactor is purged with an inert gas between the precursor pulses. The Al₂O₃ thin film in structure of the finished solar cells can play the role of both antireflection and passivation layer which will simplify the process. For this research 50×50 mm monocrystalline silicon solar cells with one bus bar have been used. The metallic contacts were prepared by screen printing method and Al₂O₃ antireflection coating by ALD method. Results and their analysis allow to conclude that the Al₂O₃ antireflection coating deposited by ALD has a significant impact on the optoelectronic properties of the silicon solar cell. For about 80 nm of Al₂O₃ the best results were obtained in the wavelength range of 400 to 800 nm reducing the reflection to less than 1%. The difference in the solar cells efficiency between with and without antireflection coating was 5.28%. The LBIC scan measurements may indicate a positive influence of the thin film Al₂O₃ on the bulk passivation of the silicon.