Site-selective chemical etching of GaAs through a combination of self-organized spheres and silver particles as etching catalyst

Microfabrication of the n-GaAs substrate surface was investigated by a combination of colloidal crystal templating, electroless plating and subsequent metal-assisted etching using noble metals as a catalyst. Ag and Cu nanosized particles were deposited site selectively to form metal-honeycomb patterns on GaAs using self-organized polystyrene spheres as a mask. By Ag-assisted etching, GaAs was effectively etched into a convex-array structure. Different anisotropic etching patterns were observed throughout the substrate after Ag-assisted etching, by changing the crystal-face orientation of n-GaAs from (1 0 0) to (1 1 1).     

Site-selective chemical etching of silicon using patterned silver catalyst

Si convex arrays and Si hole arrays with ordered periodicities were fabricated by the site-selective chemical etching of a Si substrate using patterned Ag nanoparticles as a catalyst. Ag particles were deposited selectively on the Si substrate by a combination of colloidal crystal templating, hydrophobic treatment and subsequent electroless plating. The obtained Ag patterns were of two different types: network-like honeycomb and isolated-island microarrays. The transfer of ordered patterns fabricated by Ag plating onto the Si substrate could be achieved by the selective chemical etching of a Ag-coated Si area using Ag particles as the etching catalyst. On the basis of this process, it is possible to fabricate negative and positive patterns by changing the arrangement of deposited Ag patterns.     

Cu/S-TiO2光催化剂的制备及其可见光催化性能

分别采用化学镀铜法、化学还原法、浸渍法制备了3种Cu负载的S-TiO2光催化剂,综合利用UV-Vis、XRD、XPS、EXAFS、SEM和FESEM技术对制备的Cu/S-TiO2光催化材料的结构和光电子性能进行了表征.结果表明,化学镀铜法和浸渍法负载的铜物种为Cu2O和CuO,化学还原法制备的铜为Cu和Cu2O.化学镀铜法制备的Cu/S-TiO2光催化剂不仅对可见光具有很强的吸收能力,而且负载的铜物种连续、均匀地分散在S-TiO2表面,这种结构有利于光生电子的捕获、转移和分离.因此,化学镀铜法制备的Cu/S-TiO2在不同可见光波段(λ>420 nm,λ>500 nm)条件下光催化重整甲醇水溶液制氢反应中都表现出最高的催化活性,同时在模拟太阳光条件下以及稳定性实验的测试中也表现出优秀的性质,因此对其催化作用/反应机理进行了探讨.     

Synthesis of nickel nanoparticles supported on metal oxides using electroless plating: Controlling the dispersion and size of nickel nanoparticles

Nickel nanoparticles supported on metal oxides were prepared by a modified electroless nickel-plating method. The process and mechanism of electroless plating were studied by changing the active metal (Ag) loading, acidity, and surface area of metal oxides and were characterized by UV–vis spectroscopy, transmission electron microscopy, scanning electron microscopy, and H₂ chemisorption. The results showed that the dispersion of nickel nanoparticles was dependent on the interface reaction between the metal oxide and the plating solution or the active metal and the plating solution. The Ag loading and acidity of the metal oxide mainly affected the interface reaction to change the dispersion of nickel nanoparticles. The use of ultrasonic waves and microwaves and the change of solvents from water to ethylene glycol in the electroless plating could affect the dispersion and size of nickel nanoparticles.     

3D amino-induced electroless plating: a powerful toolset for localized metallization on polymer substrates

The "3D amino-induced electroless plating" (3D-AIEP) process is an easy and cost-effective way to produce metallic patterns onto flexible polymer substrates with a micrometric resolution and based on the direct printing of the mask with a commercial printer. Its effectiveness is based on the covalent grafting onto substrates of a 3D polymer layer which presents the ability to entrap Pd species. Therefore, this activated Pd-loaded and 3D polymer layer acts both as a seed layer for electroless metal growth and as an interdigital layer for enhanced mechanical properties of the metallic patterns. Consequently, flexible and transparent poly(ethylene terephtalate) (PET) sheets were selectively metalized with nickel or copper patterns. The electrical properties of the obtained metallic patterns were also studied.     

聚合物基ZnO纳米线的制备和生长机理研究

采用独特的高分子溶液自组装生长方法, 在经化学镀预处理的基底上利用高分子溶液的网络络合效应制备了ZnO纳米线. 通过场发射扫描电子显微镜(FE-SEM), X射线能谱仪(EDS)等对样品的表面形貌及组成进行了观测表征. 结果显示, 纳米线直径约50 nm, 长度达到了数微米; 产物Zn、O化学计量比接近1∶1. 通过Si基底经化学镀工艺预处理和未经化学镀预处理对ZnO纳米结构、紫外吸收和PL性能影响的分析比较, 发现了化学镀Ni对于纳米线长度和直径尺寸的控制更为有效; 在PL图谱中, 经化学镀预处理的样品在中心波长385 nm出现了由激子碰撞复合所形成的近紫外发光峰. 进一步还分析了在不同的pH值和反应时间下样品的紫外吸收和光致发光性能. 通过以上实验, 讨论并提出了ZnO纳米线的生长机理及过程, 认为纳米线的生长是在化学镀催化剂和高分子双重作用下进行的.     

Synthesis of PVP stabilized Cu/Pd nanoparticles with citrate complexing agent and its application as an activator for electroless copper deposition

A simple method has been developed to synthesize Cu/Pd nanoparticles in aqueous solution in ambient condition with the addition of complexing agent, trisodium citrate. UV-vis spectra confirmed the complexing behavior of trisodium citrate and metal ions. The particles synthesized with trisodium citrate were well dispersed with particle size ranging between 3-4 nm while the particles without trisodium citrate were larger and aggregated, as demonstrated by transmission electron microscopy (TEM). X-ray diffraction patterns (XRD) indicated the formation of bimetallic nanoparticles without impurities in the complexing agent-supplemented system. In contrast, large amounts of PdO and Cu(OH)(2) were precipitated along with the formation of particles in the complexing agent-free system. X-ray photoelectron spectroscopy (XPS) revealed small amounts of oxidized Pd on the surface of particles and the existence of zerovalent Cu and oxidized Cu in particles with trisodium citrate. With a simpler process for electroless copper deposition, the Cu/Pd nanoparticle activator with less Pd metal used exhibited comparable catalytic activity to conventional Pd/Sn colloidal activator. In summary, application of Cu/Pd nanoparticles synthesized with the complexing agent as an activator suggested a novel, simpler and inexpensive process in PCB industry.     

Electron beam-treated organic monolayers as a negative resist for Cu immersion plating on Si

In the present work, we investigate selective immersion plating of Cu on n-type Si(111) surfaces chemically modified with different organic monolayers and subsequently directly patterned by an electron-beam (e-beam). The organic molecules (1-undecylenic acid, 1-decene and 1-octadecene) were covalently attached to a hydrogen-terminated Si surface. The use of such monolayers as masks for electroless copper deposition by immersion plating on Si surfaces was investigated. Clearly, a masking effect can be observed, the efficiency of which depends on the type of molecule. Further, the effect of e-beam irradiation to improve the masking properties of the organic monolayers was studied. For this, the monolayers were locally irradiated using a scanning electron microscope (SEM) equipped with a lithographic tool. The results show that e-beam-modified organic monolayers can be used as a negative tone resist for copper electroless plating. The selectivity of the Cu deposition at e-beam-untreated regions strongly depends on the applied e-beam dose and on the nature of organic molecules. By optimizing the electroless deposition parameters, homogeneous deposition with complete selectivity can be achieved, leading to high lateral resolution of the Cu patterns.Dedicated to Zbigniew Galus on the occasion of his 70th birthday.     

Gold tubes membrane with novel morphology replicated from ZnO template

Gold tubes membrane with novel morphology was fabricated on glass substrate by electroless plating gold on ZnO crystals array, and then annealing and removing the ZnO template by acid erosion. The morphology and size of the gold tubes membrane were decided by ZnO template. Hexagonal gold tubes membrane and double-wall gold tubes membrane were obtained, which enjoys some potential usage in electrode modification or chemical separation due to their huge surface area and unique geometric structure. SEM images show that those gold tubes in membrane are hollowed hexagonal columns with a closed head and an open bottom. Further researches found that two main factors determined the success of replication: the gold seeds (4-5 nm in diameter) immobilized on ZnO surface through APTMS (3-Aminopropyl-trimethoxysilane) before gold electroless plating and the annealing condition after electroless plating.     

Sedimentation and drying dissipative patterns of colloidal silica (560 nm in diameter) suspensions in a glass dish and a watch glass

The sedimentation and drying dissipative structural patterns formed during the course of drying colloidal silica spheres (CS550, 560 nm in diameter) in an aqueous suspension have been studied in a glass dish and a watch glass. Broad ring patterns were formed within 20 min in the suspension state by the convectional flow of the colloidal spheres and water. The sedimentary spheres always moved by the convectional flow of water, and the broad ring patterns became sharp with time. The sharpness of the broad rings was sensitive to the change in the room temperature and/or humidity. Colorful macroscopic structures were composed of the broad ring and wave-like patterns, and further colorful and beautiful microscopic fine patterns formed during the solidification processes based on the convectional and sedimentation structures. The drying patterns of the colloidal suspensions containing sodium chloride were different from the structures of CS550 or sodium chloride individuals, which support the synchronous cooperative interactions between the colloidal spheres and the salts.     

Nanoinks in inkjet metallization — Evolution of simple additive-type metal patterning

Recent advances in the development of stable dispersions of nanophase metal particles have allowed the direct fabrication of metal patterns (e.g., printed circuits, RFID tags, touch screens, etc.) by simple additive type inkjet processes. Such processes replace the more costly and less environmentally friendly subtractive lithographic type photoprocesses involving selective etching of photoresists and metal layers and more complex additive type process using photocatalysts for patterned metal deposition by electroless plating processes and inkjet patterning of metal catalyst or catalyst precursor for subsequent metallization by electroless plating. The recent development of electrohydrodynamic jet printing (e-jet printing), in which the ink drop is ejected under the influence of an electric field, has allowed a significant resolution increase vs. conventional inkjet printing with a piezoelectric head (printing resolution of ca. 100 nm for e-jet printing vs. ca. 20 μm for inkjet printing).     

Nanopatterning of Si(1 1 1) surfaces by atomic force microscope scratching of an organic monolayer

In this work, we demonstrate selective electroless deposition of Cu into nanoscratches produced on n-type Si(1 1 1) surfaces covered with an organic monolayer. The organic layer (undecylenic acid) was covalently attached to a hydrogen-terminated Si surface. The nanosize scratches were produced with an atomic force microscope (AFM) in contact mode using a diamond-coated tip. Copper was deposited in the scratched regions with an electroless (immersion plating) approach using a 0.05 M CuSO₄ + 1% HF electrolyte. The results show clearly that the organic layer can be used as a mask for the deposition of Cu. Optimization of the electrochemical parameters, leads to a very high selectivity and uniform and well-defined nanostructures. This process represents a novel approach for a direct patterning of Si surfaces using an immersion plating reaction.     

Fabrication of monodisperse asymmetric colloidal clusters by using contact area lithography (CAL)

We report a new fabrication method of asymmetric colloidal clusters by using contact area lithography with site-selective growth. Nanometric surface patterns (approximately 44, 60, and 81 nm in diameter) were prepared by coating surfaces with self-assembled monolayers (SAMs; octadecyltrichlorosilane (OTS) in this study) except the contact area either between colloidal particles or between colloids and substrate. Nanoscale site-specific heterogeneous nucleation and growth of oxide materials of titanium were studied using the patterns of OTS-SAMs onto the either flat or curved surfaces of SiO2. Experimental results suggest that a combination of the large difference in the surface energy between the growing and surrounding surfaces and the diffusion-controlled growth leads to complete nanoscale site specificity. We also fabricated superstructrures of silica spheres with hemispheres of titania (<20 nm in dimension) on their surfaces and discussed the optical properties of colloidal films consisting of the monodisperse asymmetric colloidal clusters in terms of photonic band gap.     

Fabrication and thermal analysis of submicron silver tubes prepared from electrospun fiber templates

Submicron silver tubes have been synthesized by a polymer-based template approach. Two different approaches to metallization, electroless deposition and exchange plating, were evaluated within the template approach. Silver films with average thickness approximately 50-100 nm were deposited on polycarbonate fibers approximately 400 nm in diameter by each technique, resulting in tubes with a diameter between 450 and 500 nm after thermal degradation of core fibers. These nanomaterials were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and scanning thermal microscopy. The thermal conductivity of the silver submicron tubes was found to differ depending on the method of preparation, with tubes from electroless plating possessing relative thermal conductivity values that were 1 order of magnitude higher than that from exchange plating, 3000 W/m x K and 660 W/m x K, respectively. Interestingly, these results indicate that silver submicron tubes possess higher thermal conductivity than the bulk metal. This observation is discussed in the context of the continuous conduction path of the tubes and their high surface area-to-volume ratio.     

Sedimentation and drying dissipative patterns of binary suspensions of colloidal silica spheres having different sizes

The sedimentation and drying dissipative structural patterns were formed during the course of drying binary mixtures among colloidal silica spheres of 183 nm, 305 nm, and 1.205 μm in diameter in aqueous suspension on a watch glass, a glass dish, and a cover glass, respectively. The broad ring-like sedimentation patterns were formed within several hours in suspension state for all the substrates used. Colorful macroscopic broad ring-like drying patterns were formed for the three substrates. In a watch glass, macroscopic drying patterns were composed of the outer and inner layers of small and large spheres, respectively. The two colored layers were ascribed to the Bragg diffractions of light by the dried colloidal crystals of the corresponding spheres. The width ratio of the layers changed in proportion to the mixing ratio of each spheres. In a glass dish, wave-like macroscopic drying patterns were observed in the intermediate areas between the outside edges of the broad ring and the inner wall of the cell. On a cover glass, the sphere mixing ratios were analyzed from the widths of the drying broad rings of the small spheres at the outside edge. High and distinct broad rings of small spheres and the low and vague broad one formed at the outer edges and in the inner area, respectively. Drying dissipative pattern was clarified to be one of the novel analysis techniques of colloidal size in binary colloidal mixtures.     

化学镀镍诱发过程的研究 I:金属催化活性的鉴别和反应机理

Electroless plating is known to be an autocatalytic process. For the reaction to start, the substrate metall should be either catalytic or activated by a suitable catalyst. For example, steel and nickel can be plated directly, but in the case of copper or brass, catalytic metal inducing is need. In this paper, the catalytic activity of different metals and their inducing effects were in vestigated by measuring stationary potentials nd stationary potential-time curves. Experimental results showed: (1) The stationary potential of metal provides a simple parameter to estimate the catalytic activity of metals in electroless nickeling. When 1-hydroxyethylidenediphosphonic acid (HEDP) aelectroless nickeling bath containing NaH2PO2 as reducing agent is used, electrolessnickeling may proceed spontaneously, if the stationary potential of metal is more nagative than -0.60V, no matter whether nickel (autocatalytic active) or other metals(non-autocatalytic active) is used as substrate. (2)When an autocatalytic meta is in contact with the substrate metal in the bath, a sudden decrease of stationary potential is observed. The whole inducing process could be finished within 0.5-2 sec. (3) The stationary potential of electroless nickeling coating in HEDP bath at 80`C is-0.72V, consequently nickel coating itself is a catalytic active metal. Once an electroless nickeling coating is deposited on a substrate metal, electroless nickeling reaction can then proceed continuously. (4) The sufficient conditions of electroless nickeling in HEDP bath containing NaH2PO2 are that the stationary potential of substrate metal must be more nagative than -0.60V and that the temperature of electroless nickeling bath should be higher than 50`C. (5) Inducing mechanism of electroless nickeling can be explained with chemical cell consisting of substrate metal and catalytic metal. Electrons from catalytic metal would suddenly decrease the stationary potential of substrate metal, H+ and Ni2+ complex ion would be reduced on the substrate me     

Sedimentation and drying dissipative patterns of colloidal silica (305 nm in diameter) suspensions in a glass dish and a watch glass

Sedimentation and drying dissipative structural patterns formed in the course of drying colloidal silica spheres (305 nm in diameter) in aqueous suspension have been studied in a glass dish and a watch glass. The broad ring sedimentation patterns formed within several tenth minutes in suspension state by the convectional flow of water and colloidal spheres. The sedimentary spheres always moved by the convectional flow of water, and the broad ring patterns became sharp with time. The width of the broad rings was sensitive to the change in the room temperature and/or humidity. In other words, the patterns became sharp or vague when the room parameters decreased or increased. Colorful macroscopic drying structures were composed of a broad ring and the wave-formed patterns. Iridescent colored fine patterns formed in the solidification processes on the bases of the sedimentation patterns. Beautiful drying patterns were observed for the suspension mixtures of CS300 and NaCl, and were different from the structures of CS300 or NaCl individuals, which support the synchronous cooperative interactions between the colloidal spheres and the salt.     

胶体刻蚀——纳米结构化表面的构筑与应用

综述了近年来胶体刻蚀领域的研究进展, 分别讨论了基于胶体微粒和胶体晶体为模板的可控沉积与可控刻蚀及在固体平面基质、曲面基质和气液界面等不同基质上构筑结构化表面的方法. 同时还探讨了利用胶体刻蚀方法形成的微纳结构在光、电、磁以及表面润湿和生物学等方面的应用.     

化学镀镍诱发过程的研究 II.用电子能谱研究诱发过程

In the previous paper, it was reported that a sudden decrease down to -0.6V and lower in stationary potential was observed from the stationary potential-time curve and the reaction of electroless nickeling could be induced by metallic iron catalyst when it was in contact with substrate metallic copper. In this paper, AES and XPS surface analysis and depth profile technique was employed to investigate the surface and depth distribution of Ni, Cu, Fe and P in the nickel coating deposited on the substrate metal. The experimental results showed that there was a thin adsorption layer consisting of C, S and Cl. The pure electroless nickel deposition, its Ni/P ratio being about two, existed under the adsorption layer. A layer with rapidly changed Ni/P ratio occurred close to the surface of substrate metal, under this layer the substrate metal was alloyed with Ni and P, thus becoming Cu-Ni-P alloy. The ratio of components in this alloy was found to be Cu:Ni:P=56:36:5. This fact explained why the electroless nickel deposition can preferably adhered to the substrate metal. In inducing process, Fe was not detected by AES from the substrate metal and nickel deposition. Thus it showed that the inducing reaction takes place without the deposition of inducing metal.     

Facile synthesis and characterization of uniform CdS colloidal spheres

Uniform CdS colloidal spheres have been successfully synthesized via a simple hydrothermal method.X-ray diffraction(XRD) analyses indicate that the products exhibit a hexagonal structure.Scanning electron(SEM) and transmission electron microscopy (TEM) are used to characterize CdS colloidal spheres.The final size of the spheres may be selected from a range of 71±2 nm to approximately 181±5 nm by changing the amount of polyvinylpyrrolidone(PVP) and hexamethylenetetramine(HMT).The CdS colloidal spheres are not obtained in the absence of either of the capping agents.A synergistic effect between HMT and PVP is proposed to be crucial for the formation of colloidal spheres.