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Traditional methods for surface pretreatment of carbon fibers often rely on the use of precious metals like palladium and silver as activators to enhance surface reactivity through redox reactions, achieving metallization. However, such approaches are costly and economically inefficient. This study employed a cost-effective copper (Cu)-nickel (Ni) colloid mixture as an activator and investigated its effectiveness in enhancing surface reactivity. Meanwhile, it examined the influence of various parameters, such as pH value, reducing agent (formaldehyde (HCHO) concentration, temperature, and deposition duration, on the morphology and structure of copper-electrodeposited carbon fibers. To characterize the treated samples, scanning electron microscope (SEM) and x-ray photoelectron spectrometer (XPS) were adopted, shedding light on the mechanism underlying copper electrodeposition on the carbon fiber surface. The results indicate that Cu-Ni colloid mixture activation exhibits significant improvements. The optimal conditions for uniform and smooth copper electrodeposition on the carbon fiber surface identified as follows: a pH value of 13.5, a HCHO concentration of 15 ml L ^−1 , a temperature of 50 °C, and a deposition duration of 5 min. Consequently, these results represent a cost-effective alternative to traditional precious metal-based activation methods, with promising applications in surface pretreatment for carbon fibers.

Research on cost-effective and high-efficient catalysts for overall water splitting is urgent, and iron group metal borides (IMBs) are a promising candidate. Here, FeCoNiB nanoparticles anchoring on vertically aligned B-doped graphene array (FeCoNiB/BVG) by electroless plating are synthesized for overall water splitting, and FeCoNiB nanoparticles anchoring on other heteroatom-doped graphene substrates (FeCoNiB/XVG, X = N, P, S, O) are prepared for comparison. FeCoNiB/BVG exhibits the best performance with HER and OER overpotential of only 88 mV and 149 mV in 1.0 M KOH, respectively. And FeCoNiB/BVG has a very strong stability for 15 h and the Faraday efficiency of about 94%. The XPS results prove that the best performance of FeCoNiB/BVG is due to the synergistic effect between B in BVG and B in FeCoNiB. This work provides a reference for the rational design of nonnoble metal-based electrocatalysts and promotes the application of non-noble metal-based electrocatalysts in the water electrolysis industry. [ABSTRACT FROM AUTHOR]

Ion-track etching represents a highly versatile way of introducing artificial pores with diameters down into the nm-regime into polymers, which offers considerable synthetic flexibility in template-assisted nanofabrication schemes. While the mechanistic foundations of ion-track technology are well understood, its potential for creating structurally and compositionally complex nano-architectures is far from being fully tapped. In this study, we showcase different strategies to expand the synthetic repertoire of ion-track membrane templating by creating several new 1D nanostructures, namely metal nanotubes of elliptical cross-section, funnel-shaped nanotubes optionally overcoated with titania or nickel nanospike layers, and concentrical as well as stacked metal nanotube-nanowire heterostructures. These nano-architectures are obtained solely by applying different wet-chemical deposition methods (electroless plating, electrodeposition, and chemical bath deposition) to ion-track etched polycarbonate templates, whose pore geometry is modified through plastic deformation, consecutive etching steps under differing conditions, and etching steps intermitted by spatially confined deposition, providing new motifs for nanoscale replication. [ABSTRACT FROM AUTHOR]

FeCoxNiyB nanoparticles with tuned cationic ratio integrated on Vertically Aligned Boron-doped Graphene Array (FeCoxNiyB@B-VG) electrocatalysts towards water splitting are successfully prepared by electroless plating. For a specific composition, FeCo66.7Ni33.3B@B-VG electrocatalyst exhibits the highest electrocatalytic activity towards hydrogen evolution reaction, with low overpotentials of 125 and 157 mV at ?10 and small Tafel slopes of 52 and 47 mV dec-1 in 1.0 M KOH and 0.5 M H2SO4 solution, respectively. FeCo66.7Ni33.3B@B-VG electrocatalyst displays remarkable catalytic activity towards oxygen evolution reaction by showing low overpotentials of 200 and 569 mV at ?10 and small Tafel slopes of 34 and 225 mV dec-1 in 1.0 M KOH and 0.5 M H2SO4 solution, respectively. The result of stability test exhibits that FeCo66.7Ni33.3B@B-VG electrocatalyst has long-term stability for at least 10 h towards water splitting in a wide pH range. And the faraday efficiency of FeCo66.7Ni33.3B@B-VG towards water splitting is around 90%. This study helps to explore the effect of variable cationic ratio in the fabrication of non-noble electrocatalyst to achieve enhanced electrocatalytic activity for water splitting in a wide pH range. [ABSTRACT FROM AUTHOR]

In this study, a process for wet metallization on glass substrate involving adhesive electroless plating (ELP) is developed by integrating two material innovations. The first involves functionalizing a polymer-capped Pd nanocluster with amino silane compound to strengthen the adhesion between the ELP metal film and substrate. The second involves an additional nanoscaled TiO2 layer serving as the adhesion promoting layer (APL) coated on glass before metallization. After investigation with various tools, ELP metal film was observed to penetrate the mesoporous structure of TiO2 APL, reinforcing the adhesion of metallized film on glass through the mechanical anchoring effect. The formation of an interlayer between TiO2 APL and glass is not observed. A T-peel strength of 325 N m−1 is achieved. According to fracture analysis, the metal film/TiO2/glass structure breaks inside TiO2 APL, not TiO2 APL/glass, suggesting that further engineering developments are required to improve TiO2 APL coating. [ABSTRACT FROM AUTHOR]

TaN in conjunction with adhesive Ta is a key barrier component of Cu-Damascene structure. However, the limited scalability and stability of TaN pose a dire need of an alternative molecularly thick (⩽1 nm) barrier. To this end, the feasibility of anodizing 2-nm-thick Ta films with a mild ethanol based solution, rather than the commonly used strongly acidic (aggressive) chemical electrolytes, to enhance the formation of (3-aminopropyl) trimethoxysilane (APTMS) monolayer barrier is studied. Performing the anodization in an H2O-containing (1%) ethanol solution results in a prompt oxidization of the Ta film surface into fully passive Ta2O5 layer with extremely smooth topography, subsequently facilitating the growth of a fully oriented monolayer serving triply as a seed adsorber (for electroless Cu plating), barrier and adhesion promoter. Using Ta (pristine)/Cu [and Ta (pristine)/SAM/Cu] as a control, Ta (anodized)/SAM/Cu exhibits markedly higher adhesion strength (25.2 vs <1 MPa) and resistance against thermal failure (>500 vs 425 °C) of Cu. H2O is heavily involved in the anodization efficiency of the Ta films and is the key underlying factor deciding orientation ordering and barrier capacity of the monolayer fabricated. This is related to H2O-enhanced surface hydroxylation and Ta2O5 passivation of Ta. [ABSTRACT FROM AUTHOR]

Porous anodic aluminum oxide (AAO) films have great potential for micro and nano fabrication. Development of metallization techniques for AAO films is necessary for AAO device fabrication. In this work, a process for electroless Cu plating on AAO films was investigated. A quick Pd2+ removal process after activation improved the adhesion between plated copper (Cu) layer and AAO films. Since the Pd catalyst at the AAO top surface was effectively removed by a complex agent, the plating reaction started approximately 15-20 µm deep in the nanopores. The Cu was continuously deposited to the top of the nanopores and finally covered the AAO surface. The adhesion strength between the Cu films and AAO films measured by the 90° peeling test method was over 0.5 kN/m. Successful electroless Cu plating on AAO is an all-wet chemical batch process that does not require sophisticated fabrication facilities, and can be used as a low-cost metallization process for producing AAO microdevices. [ABSTRACT FROM AUTHOR]

In the study, PS/Ag composite microspheres with polystyrene (PS) core and silver shell were synthesized by ultrasonic electroless plating. The samples were characterized by SEM, FTIR and XRD. The effects of times of sensitization and silver plating, mass ratio of AgNO _3 to PS microspheres and stirring method on the preparation and dispersion of PS/Ag microspheres were studied. The results show that the more times of sensitization and silver plating, the more uniform the silver deposition on the surface of microspheres. When the mass ratio of AgNO _3 to PS microspheres is 2: 1, it can promote the uniform coating of silver shell and reduce the content of free silver. Ultrasonic assisted electroless plating for 10 min can prevent PS/Ag microspheres from agglomerating and improve the speed of electroless plating. The thickness of the silver shell on the surface of the PS microsphere is about 200 nm.

In order to prevent the copper coating on the carbon fiber surface from oxidizing and falling off, the tin coating is plated on the surface of copper-coated carbon fiber. In this paper, the copper-tin composite coating with different thicknesses of tin coatings were successfully prepared by electroless plating. The results show that with the increasing of electroless tin plating time, the thickness of the copper-tin composite coating increases. The test results of the bonding force between the composite coating and the carbon fiber show that the coating bonding force is the best when the thickness of composite coating is between 1.31 μ m and 1.55 μ m. This is due to the formation of copper-tin intermetallic compounds preventes direct contact between the copper coating and oxygen, which can effectively inhibit the oxidation of the copper plating layer, thereby making the plating layer less likely to fall off. However, the excessively thick tin coating would increase the internal stress of the coating, and promote the generation of cracks on the surface of the composite coating, which would cause the composite coating to fall off. This research will provide new ideas for the preparation of high-performance copper plating on the surface of carbon fiber, and provide an important theoretical and practical basis for the application of copper coatings.

Novel soft magnetic materials can be obtained by altering the material properties of soft magnetic alloys, including the morphology, composition, crystallinity, and grain size. The magnetic properties (such as saturation magnetization and coercivity) of soft magnets are significantly dependent on the grain boundaries,which control the magnetic domainwallmovement.Herein,we develop a two-step electroless plating method to control the morphology and grain size of FeCo films, to obtain excellent magnetic properties. To control the degree of polarization, the chemical composition was altered by varying the electroless plating conditions, such as electrolyte concentration and reaction temperature. The grain size and crystallinity of the FeCo alloys were dramatically affected by the reaction temperature, because grain growth occurs dominantly at 90◦C, whereas nucleation only occurs at 50◦C. By simply controlling the electrolyte temperature, an FeCo film embedded with micron-sized FeCo grains was synthesized. The high crystallinity and large grains allowed high magnetization, and the high magnetic exchange between FeCo grains of different sizes gave low coercivity. [ABSTRACT FROM AUTHOR]

Fe--Ni--B alloy thin films were prepared by using an electroless plating method, and their thermal-expansion behavior, thermal-stress generation, and crystal structure were evaluated. By heating from 30°C to 300°C, the electroless-plated Ni--5 wt%B alloy film showed a marked increase in tensile stress at approximately 270°C, which is caused by a phase separation from the amorphous Ni--B alloy into a highly crystalline Ni and Ni3B compound. The coefficient of thermal expansion (CTE) of electroless-plated Ni--B alloy film from 300°C to 30°C, after heating to 300°C, was 14 ppm/K. In contrast, the electroless-plated Fe--Ni--B alloy film in the Invar composition range had a small CTE (8 ppm/K to 9 ppm/K) and no substantial change in crystal structure during heating to 300°C. As a result, the Fe--Ni--B alloy film on the silicon substrate (CTE = 3 ppm/K) exhibited a low thermal stress compared with the electroless-plated Ni--B alloy film. Thus, it is suggested that the electroless-plated Invar Fe--Ni--B alloy films are suitable as an under-bump metal layer from the viewpoint of the thermal-expansion behavior. [ABSTRACT FROM AUTHOR]

Pt and PtSn catalysts were synthesized by a single-step electroless process on hierarchical three-dimensional electrodeposited branched metallic Sn structures (BMS). The controlled electrodeposition of Sn on a carbon-paper substrate resulted in a high surface area of BMS, on which the Pt and PtSn alloy catalysts were deposited as thin layers. The PtSn species were reduced on the Sn substrate from Pt-Sn complexes formed in the solution. Several synthetic aspects were studied, such as the acidity of the electroless solution and the electroless process time span. The prepared electrodes were applied as anodes in direct methanol fuel cells.Methanol oxidation on these electrodes exhibited a specific peak power density of 476 mW mg-1 Pt at 0.45 V, 90 mA cm-2 and 70◦C, using only 75 μg cm-2 of Pt, which is significantly higher than previously reported platinum-based catalysts. [ABSTRACT FROM AUTHOR]

Material properties of electroless deposited copper film suitable for electronic circuits have been studied on Silver nanoparticle inkjet-printed polyimide substrate. The optimized process includes silver nanoparticle seed printing, sintering at 300°C, followed by electroless deposition. The result was a highly conducting copper metallization with an improved resistivity of 2.1μΩ.cm compared to only printed silver. We also present composition analysis by XPS and structural characterization by FIB-SEM and profilometry. FIB-SEM, XPS, and XRF were integrated together to deduce the kinetics of electroless deposition on the highly porous silver nanoparticle seed. The results and the model indicate that the copper deposition is in two consecutive stages: (a) copper deposited inside the seed silver layer to fill the porous channels formed after annealing (b) the copper deposited uniformly on top of the filled pores. The effective conductance is a result of the two elements, silver and copper, the composite formed in the seed and the dense polycrystalline copper thin film deposited on the top of the seed. [ABSTRACT FROM AUTHOR]

Ni-P alloy coatings with a phosphorus content of 11.65 wt% were deposited by electroless plating. The as-plated nano-amorphous Ni-P alloy coatings were heated in air for 1 h at 200–500 °C. By using an atomic force microscope and the x-ray diffraction method, the nanocrystalline morphology and the crystallization phase identification of the coatings were studied. The corrosion behavior of the coatings in the 3.5 wt% NaCl solution was analyzed using polarization curves and impedance spectroscopy. It was observed that the corrosion behavior of the coatings was affected by the change in the nanocrystalline structure; during the heat treatment, the nanocrystalline structure of the coating alloy undergoes sequential changes from amorphous → the adjustment of amorphous → precipitated phase → crystalline. Meanwhile, the corrosion behavior of the coating alloy has also changed from uniform corrosion controlled by charge transfer → uniform corrosion controlled by diffusion → grain boundary corrosion. The Ni phase and the Ni _3 P phase developed a compact and dense nanocrystal layer on the surface of the coating alloy, in which the best performance by the corrosion resistant coating can be found.

A new electroless copper plating process, namely, an alternating one-side air stirring method, was studied to improve the throwing power of high-aspect-ratio through-holes in multilayer printed wiring boards. The throwing power can even be improved for throughholes of a 40-aspect ratio under an appropriate flow velocity of the solution because the generation of differential-pressure between the front and the back of the board enhances supplying the solution into the through-holes. The necessary flow velocity can be estimated by considering the consumption rate of copper ions in a through-hole and calculating it on the basis of Bernoulli's and Hagen-Poiseuille's equation [ABSTRACT FROM AUTHOR]

Hollow copper microspheres with pore size about 3 µm and spherical shell around 150 nm were successfully prepared by electroless plating using polystyrene (PS) as sacrificial templates and the kinetics were studied concerning the empirical rate law. The effects of plating bath composition on the amount, microstructure and composition of the deposited copper shells were investigated. pH was the most important factor for copper deposition rate and amount of copper deposits. The amount of by-product Cu2O decreased with increasing pH values and the deposited copper agglomerated when pH value reached 13.41. The addition of stabilizers (2, 2-bipyridine, potassium ferrocyanide and methanol) had a very negative effect on the microstructure of the deposited copper shells. PS templates were removed by sintering and the remanent copper deposits with high purity maintained good spherical shell structure. In addition, the kinetic equation of electroless copper plating (ECP) using PS as the substrate was determined and the activation energy (Ea) was 59.77 kJ · mol-1. The prepared hollow copper microspheres with high porosity are ideally suitable for synthesizing energetic materials and this method might also be used for fabricating other hollow metal microspheres. [ABSTRACT FROM AUTHOR]

Manganese-doped copper interconnects are known to provide superior electromigration resistance and thus are attractive for further downscaled interconnect metallization in future high-performance microprocessors. In the present study, we report on Cu-Mn (copper-manganese) fabricated by electroless deposition. Using tartrate-complexed electrolytes, we achieved electroless plating of Cu-Mn with (4.0 ± 0.5) at.% Mn. Electrochemical studies determined the most likely oxidation state of the Mn in the deposit to be +2. This suggests incorporation of MnO or Mn(OH)2 during deposition. After heat-treatment of the Cu-Mn films, X-ray photoelectron spectroscopy indicated Mn segregation at the film surface. Moreover, transmission electron microscopy demonstrates Mn segregation at Cu-substrate interface. These observations suggest that Mn transport in electroless-deposited Cu-Mn can be exploited to engineer future interconnects with improved reliability and 'self-forming' barrier properties. Challenges to be addressed in future studies are highlighted. [ABSTRACT FROM AUTHOR]

We report an all-solution, simple process (DC plating with single additive) for metallizing high aspect ratio (AR = 5 and AR~12) through vias in ultrathin glass (thickness ~100 um). Highly uniform and continuous Cu seed layer is first achieved by a simple surface modification, Sn/Pd catalyst adsorption and Cu electroless plating. Subsequently, the vias are filled by DC plating in the presence of a single additive nitrotetrazolium blue chloride (NBT). The strong inhibition effect of NBT is exploited to first bridge the center of the vias followed by filling of two blind vias. [ABSTRACT FROM AUTHOR]

Hybrid electro-electroless deposition (HEED) is the unification of electroplating and electroless deposition in a single electrolyte for the reduction of separate and distinct metals/alloys. The novel combination has the capacity to create unique layered and alloyed deposits by having electroplating and electroless deposition each target a different metal ion within the electrolyte. Electroplating from a Co/Ni-P electrolyte has the capacity to produce Co(Ni-P) layers having over 60% Co atomically. Similarly, electroless Ni-P layers produced from the same electrolyte contain atomically at most 2% Co. Both the electroplating and electroless deposition processes can be tuned to allow greater, or lesser, Co alloying in each layer. The sequential deposition of electroplated Co(Ni-P) and electroless Ni-P within the single electrolyte is used herein to produce a compositionally modulated pentalayer deposit. [ABSTRACT FROM AUTHOR]

Several chromium-free pickling and activation processes were investigated in order to develop an eco-friendly pretreatment for electroless Ni-P plating on magnesium alloy. The coatings obtained from etching only in H3PO4 solution exhibit poor adhesion due to the existance of an interlayer. Meanwhile, a corrosion model of Mg alloy in H3PO4 solution was proposed. When fluoride was added into the pickling solution, the adhesion of the coatings was also unsatisfied because of the bad mechanical interlocking action. By comparison, the coatings obtained from pickling in H3PO4 solution followed by NH4HF2 activation displayed wonderful properties in both adhesion and corrosion resistance. [ABSTRACT FROM AUTHOR]

To inhibit the detrimental diffusion of copper into silicon devices, an effective barrier is strongly demanded. In this study, copper(rhenium) alloy films were successfully electroless- and electroplated on silicon substrates for self-forming an ultrathin rhenium barrier layer. In pure copper films, the interdiffusion of copper and silicon already occurred at 400°C, forming silicides and increasing the electrical resistivity of the films. In comparison, not any silicide formation was observed in the electroless- and electroplated copper(rhenium) alloy films with minor incorporations of rhenium for 0.10 and 0.39 at% until 600 and 500°C, respectively, attributed to the prior segregation of rhenium and the self-formation of rhenium barrier layer at the copper/silicon interface at 400°C. A zero solubility of rhenium in copper and a small solubility in palladium catalysts facilitate the separation of rhenium from copper. The kinetics of rhenium segregation follows uphill diffusion, and the diffusivity of rhenium in copper at 400°C is estimated to be 1.5 x 10-17 cm²/s. [ABSTRACT FROM AUTHOR]

An ultrasonic-assisted method for electroless Ni-P plating on dual-phase Mg-Li alloy is proposed. Environmentally-friendly Ce(NO3)3-KMnO4 solution was successfully applied for the pre-treatment. Uniform and compact Ni-P coatings with fine structures have been successfully obtained. The Ni-P coatings are mixed with amorphous-crystalline features and well adhered to the substrates. The corrosion resistances were investigated by electrochemical impedance spectroscopy, open circuit potential, potentiodynamic polarization and hydrogen evolution tests. The results indicate that ultrasonic processing significantly improves the corrosion resistance of Ni-P coatings due to the formation of uniform, dense and fine structures, which strengthen the passive film. [ABSTRACT FROM AUTHOR]

Direct electroless deposition, i.e., without using a sacrificial anode or substrate activation, of iron-boron (FeB) films on copper substrates is reported. Electroanalytical techniques including polarization measurements of oxidation and reduction half-reactions are employed to optimize process parameters, thereby enabling direct nucleation and sustained growth of electroless FeB films on copper. Scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction are used to characterize the film morphology, the deposition rate, the deposit composition and crystallinity. Optimized electroless FeB films have a growth rate of 0.24 μm/hr, are smooth and amorphous, and exhibit acceptable corrosion resistance. [ABSTRACT FROM AUTHOR]

A sonochemical Pd seeding method for Cu electroless deposition (Cu ELD) is introduced in this study. Pd seeds, used as catalysts for Cu ELD, were deposited on a Ta/TaN diffusion barrier by ultrasound irradiation. The existence of Pd seeds on the substrate by irradiation was confirmed with X-ray photoelectron spectroscopy and atomic force microscopy. Cu ELD on the Pd-seeded substrate was successfully achieved. The formation of an electroless Cu film was strongly affected by the process parameters for sonochemical Pd seeding, such as the distance between the tip of the ultrasonic probe and a substrate, chemical composition of the seeding solution and ultrasound irradiation time. Those parameters were decisive factors in changing the deposition uniformity and number density of the Pd seeds. From the parametric study, we obtained a continuous electroless Cu film with good adhesion strength and low resistivity at the optimum condition. [ABSTRACT FROM AUTHOR]

Co-B-P-W alloy films were deposited by the electroless plating method on Cu foil and on Si wafer with a sputtered PVD TaN/Ta barrier and Cu seed substrate. The effects of concentration of the reactants and temperature on the deposition rate were investigated. By variation of electroless plating solution composition, Co-W-P-B coatings containing different amounts of boron, phosphorus and tungsten can be obtained under slightly acid conditions. Using operating conditions selected Co-W-P-B coatings containing 0.5-10.0 at% W, 0.5-16.0 at% B and 1.5-6.0 at% P can be obtained. The induction period of the electroless deposition reaction depends on solution composition, but can be effectively shortened by elevation of the temperature of working solution. [ABSTRACT FROM AUTHOR]

We report here the formation of an electrode through a selective electroless plating process. It consists of pre-treatment, selected Ni electroless plating, and Cu electroless chemical plating. Through the selective electrode formation technique using Pd/Ni/Cu, we established a high-efficiency and low-cost process for the manufacture of crystalline silicon solar cells. Measurements with a solar simulator showed that an open-circuit voltage of 0.684 V, short-circuit current density of 32.3 mA/cm², form factor of 75.39%, and an efficiency of 18.21% was obtained for a monocrystalline silicon solar cell. [ABSTRACT FROM AUTHOR]

Electroless copper deposition was investigated on epoxy laminate substrates (Isola 185HR) using a silver-based catalyst, and a non-roughening surface treatment method based on sulfuric acid. The current challenges in electroless copper deposition include (i) high cost of Pd-based catalysts, (ii) deterioration of electrical performance of deposited metal at high frequency due to electron scattering at the roughened surface, and (iii) limited adhesion strength of electroless layers to substrates. We investigated an electroless copper deposition procedure composed of a H2SO4 surface pretreatment, two-step Sn/Ag nano-colloidal catalyst seeding, and immersion in a traditional formaldehyde-containing electroless copper bath. The H2SO4 pretreatment activated the epoxy surface for electroless deposition. Other strong acids did not lead to deposition. The H2SO4 treatment cleaned the substrate and provided the adhesion of the catalyst and electroless copper without increasing the surface roughness. XPS results showed a decrease in the carbonyl groups (C=O), and acid/ester functionalities (O-C=O) at the surface. Adsorbed sulfate on the substrate from the H2SO4 treatment led to Sn(II) sensitization. The tin-silver activation step resulted in Sn(IV) and Ag(0) products in the form of a Sn/Ag nano-colloidal catalyst. The Sn/Ag colloid acted as a catalyst for electroless copper deposition on the epoxy laminate substrates. [ABSTRACT FROM AUTHOR]

Glass has gained interest as a material for interposer technology due to its low/adjustable thermal expansion coefficient, low cost, good dimensional stability and availability in large panels compared to silicon substrates. However, the metallization of glass constitutes a major challenge owing to the notoriously poor adhesion between glass and metals. In this work, strategies for improving the adhesion to the glass surface and for providing at the same time continuous coating of through glass holes (TGHs) are explored. As result, a hybrid approach for glass metallization based on sputtering of a thin Ti-Cu layer and subsequent coating by electroless Ni deposition is introduced and developed. The proposed approach takes advantage of the good adhesion of very thin sputtered films on glass surfaces and combines this with the ability of electroless plating to bridge center regions of high aspect TGHs that are inaccessible to metallization by sputtering. Robust layers deposited by the hybrid method, shown to continuously coat the surface and TGHs, allow for further Cu elctrodeposition on the way to final circuitry. Approaches explored for seeding, coating and further metallization are described in detail. Results of cross-section analysis, optical microscopy, and SEM are also presented. [ABSTRACT FROM AUTHOR]

A rice-straw-like silicon nanowire (SiNW) array was developed for hydrogen gas sensing applications. The straight-aligned SiNW array sensor was first fabricated by the metal-assisted electroless etching (MAEE) technique. Rice-straw-like SiNW arrays were formed using a repeated MAEE technique. Hydrogen sensing characteristics were measured for gas concentrations from 20 to 1000 ppm at room temperature. The rice-straw-like SiNW-array-based hydrogen gas sensor performed with low noise and a high response (232.5%) for 1000 ppm hydrogen gas. It was found that the rice-straw-like SiNW-array hydrogen gas sensor had a much better response (approximately 2.5 times) than the straight-aligned SiNW-array sensor. The rice-straw-like SiNW-array structure effectively increased the surface area and the concentration of silicon oxide, which provided additional binding sites for gas molecules. Thus, the rice-straw-like SiNW-array-based hydrogen gas sensor possessed good sensing properties and has the potential for mass production of sensing devices. [ABSTRACT FROM AUTHOR]

Amorphous iron-molybdenum-boron deposits were obtained by electroless plating with a metal couple made up of copper & aluminum sheets. The films were prepared on the copper sheet in a bath containing ferrous sulfate, sodium potassium tartrate, sodium hydroxide, potassium borohydride and sodium molybdate. The deposits have perfect chemical resistant and good surface appearance. The co-deposited element of Mo with the Fe and B atoms improved the glass formation ability (GFA) of the alloys and extended the glass-forming region (GFR) of B content to 6.63 to 30.1 at%. The aggregation of molybdenum atoms was found in the present specimens. The microhardness of the deposits increases with the increment of B content in the deposits, which may be attributed to the strengthening of partial bonds formed by overlapping s-p hybrid orbits of boron atoms with the s-p-d orbits of iron and molybdenum atoms. [ABSTRACT FROM AUTHOR]

The combination of our improved laser confocal microscopy with the differential interference microscopy technique (LCM-DIM) is capable of resolving the monatomic steps with heights of ca. 0.25 nm on Au(111) and Pd(111) surfaces and even 0.14 nm on Si(100) in aqueous solutions. LCM-DIM can also follow dynamic movement of monatomic steps in a large area with short acquisition times (2-10 frames/s), indicating that the LCM-DIM is a powerful in-situ method for evaluating various reactions at solid/liquid interfaces with atomic layer resolution. In this paper, we demonstrate the capability of LCM-DIM for the evaluation of the electrodeposition of Au on an Au(111) surface. It is shown that the Au deposition occurs mainly at atomic steps resulting the layer-by-layer growth at potentials near the onset of cathodic currents over the entire area (ca. 100 x 100 µm square). New small islands with a monatomic height were also observed on atomically flat terraces during the deposition. These islands expanded in the lateral direction, resulting the formation of new layers. LCM-DIM provides direct images of dyammic growth modes in the electrochemical deposition of Au with an atomic layer resolution. [ABSTRACT FROM AUTHOR]

Magnesium alloys are known to have excellent physical and mechanical properties suitable for a number of industrial and technological applications. The propensity of Mg to form galvanic couples limits further industrial acceptance. This paper examines the conditions for the electroless deposition of ternary nickel-phosphorous-zinc [Ni-P-Zn] alloy films on AZ91D Mg alloys comparing the deposition with similar deposits on more traditional surfaces. The stable, aqueous, alkaline solutions used in this study do not require any pre-treatment specific to the deposition and are able to produce continuous coatings containing Zn up to around 24 wt% of the total cladding. [ABSTRACT FROM AUTHOR]

Previous studies of the authors have reported the formation of electroless Ni-B coatings on magnesium and AZ91D magnesium alloy using a chrome-free process. The substrates were pre-treated by grit-blasting and etching. In the present study, the influence of an activation stage in NH4HF2 solution is investigated. Scanning electron microscopy, X-ray diffraction, Raman spectroscopy and ion beam analysis are employed to determine the morphology, structure and composition of the treated surfaces at different stages of the electroless process. The results indicate that activation has relatively little influence on the growth rate and properties of the final coatings. However, it accelerates the coverage of the surface by Ni-B nodules at the start of the electroless treatment and, in the same period, reduces the electrochemical potential, the latter suggesting inhibition of corrosion of the substrate. Further, activation reduced the oxygen content of surfaces and led to formation of N-H species. Comparison with the earlier studies indicated that activation is of secondary importance to grit-blasting and etching for the generation of uniform coatings. [ABSTRACT FROM AUTHOR]

A high-temperature-resistant bond withstanding up to 415°C for SiC power devices is realized at 260°C with a Cu/Sn powder paste and an electroless nickel plated Si3N4/Cu circuit substrate. The bond was formed by using transient liquid phase sintering (TLPS). The bond strength tested at 300°C increases with increasing aging time at 300°C, from the original 40 MPa to 50 MPa after aging at 300°C for 200 h. This is attributed to phase transformation from Cu6Sn5 formed during TLPS to Cu3Sn in the bond during aging. We observed an η-(Cu,Ni)6.26Sn5 phase at the interface between the TLPS Cu-Sn bond and Ni(P) layer. The interface between the TLPS Cu-Sn bond and Si3N4/Cu/Ni(P)/Ag substrate exhibits very high stability, characterized by a very slow Ni(P) layer consumption rate and Ni3P growth rate. The TLPS Cu-Sn bond on a 5 μm-thick electroless plated nickel layer is expected to have a life time beyond 105 h during storage at 300°C. [ABSTRACT FROM AUTHOR]

The scope of electroless copper plating technology is evolving to applications with smaller structures and smoother substrates, where adhesion of the copper film can be hard to achieve. The extent to which different factors, such as film stress and hydrogen evolution, contribute to delamination and blister formation on smooth organic substrates is a topic of active discussion. Stress and strain evolution is reported here for a nickel- and formaldehyde-free formulation for a range of plating bath temperatures. X-ray diffraction, with the sin ²ψ method, was used to monitor the strain within the copper crystallites during and after their growth. Substrate bending measurements were used to detect the average stress of the film. This technique indicates a 60 nm wide zone of tensile stress at the interface between substrate and film. During and immediately following deposition, the average substrate stress is more compressive than implied by the strain of the Cu crystallites. After deposition, the additional compressive stress seen by substrate bending relaxes until it matches the Cu crystallite strain. Furthermore, the thermal substrate contraction effect upon termination of plating is considered, since it may influence the film adhesion. [ABSTRACT FROM AUTHOR]

The adhesion between the electroless seed layer and the buildup film substrates was studied. After the buildup film was laminated, the buildup film surface was modified by a desmear treatment from 0 to 30 rain, and electroless Cu or electroless Ni-P was plated as the seed layer on the buildup film. The Cu was then electroplated, and the post curing was carried out at 180°C for 2 h before or after Cu electroplating. The adhesion strength between the electroless seed layers and the buildup film suhstrates was measured by the 90° peel test. Increasing the desmear treatment time made the buildup film surface rougher, and consequently enhanced the adhesion strength of the electroless Cu and electroless Ni-P to the fihn. Under the same conditions, the electroless Ni-P specimen showed a higher peel strength than the electroless Cu specimens. Post curing significantly increased the adhesion strength due to the increased ductility of the metal layer after heat-treatment. In addition, the peel strength decreased as the thickness of the seed layer increased, which was also related to the mechanical properties of each metal layer. [ABSTRACT FROM AUTHOR]

Sustained silver (Ag) electroless deposition onto copper (Cu) surface was achieved from a simple and stable solution, which only containing silver salt, choline chloride (ChCI) and H2O, without using of catalyst and reductant. The mechanism of Ag deposition in ChC1-H2O solution was proven by ultra violet spectroscopy and cyclic voltammetry techniques. Through a study of the Ag coatings using atomic absorption spectroscopy, X-ray diffractometer and scanning electron microscope, we demonstrate that sustained deposition of Ag was achieved in ChCI-H2O solution with mole ratio higher than 1 ChC1 : 5 H2O and the calculated activation energy of Ag deposition was 13.0 kJ ⋅ mol-1. [ABSTRACT FROM AUTHOR]

We have realized lateral contact switches using electroless deposition of Au/Cu on Si with all the necessary features including source, gate and drain. The metallization approach is simple and effective, allowing for Au/Au contact and inducing near-zero curvature even in long (up to 1 mm length) and slender (5 μm × 5 μm) cantilever beams (spring constant is 0.02 N m-1). The switching time for these long beams is approximately 80 μs under ambient conditions. The lifetime of the fabricated switches is a function of current levels applied between the source and the drain (approximately 3000 cycles with a current load of 0.6 mA). The capacitance change between the on- and off-states of the switches is about 3 fF. [ABSTRACT FROM AUTHOR]

The characteristics of a Pd/AIGaN/GaN high electron mobility transistor (HEMT) processed using the sensitization, activation, and electroless plating (EP) deposition approach are studied and demonstrated. A dense and uniform Pd seed layer is achieved by using the additional sensitization and activation processes. Therefore, the superior characteristics in turn-on voltage ( 1.79 V), gate leakage current (9 nA), maximum extrinsic transconductance (95.8 mS/mm), and maximum drain saturation current (373.8 mA/mm) are obtained for a 1 µm gate HEMT at 300 K. As increasing the temperature from 300 to 600 K, the reduced variation and degradation rates are also found for the studied EP-gate device. Furthermore, superior hydrogen gas sensing performance, including large drain current change (34.1 mA/mm) and high sensing response (3469%), is observed under 1% H2/air ambience. Consequently, the studied EP-gate AIGaN/GaN HEMT shows the promise for high-performance electronic device and hydrogen sensor applications. [ABSTRACT FROM AUTHOR]

A systematic study of silver-catalyzed etching in (100) and (111) n-type Silicon substrates is carried out by varying the amount and the morphology of electroless deposited silver clusters. Deposition rate is very fast during the first few seconds and then it levels at a lower value of one order magnitude for both oriented wafers. For small and well-separated clusters the Si nanowires formed by the etching are aligned along the (100) axes, while for large and interconnected they are oriented along the normal to the surface. For the (100) Si substrate partially covered with small silver clusters the etching proceeds both in vertical and horizontal [100] directions. For larger coverage (70%) the Ag nanoparticles sink all together along the vertical direction. For the (111) Si substrate, when the Ag nanoparticles are isolated they sink in all the equivalent [100] directions with an irregular path; when the Ag nanoparticles begin to coalesce uniform domains of Si nanowires aligned along [100] directions are formed. When the silver clusters are well interconnected (70% of coverage), the etching is vertical. Silver coverage is then another experimental parameter to induce a preferred orientation of the etched Si nanowires. [ABSTRACT FROM AUTHOR]

Electrochemical surface areas (ESAs) were used to estimate the specific activities of different-sized Ag nanoplates (NPLs), which were used as novel catalysts for electroless copper deposition (ECD). Based on the consideration of ESAs and deposition kinetics measured using an electrochemical quartz crystal microbalance, the mean specific activities of NPLs with sizes of 74 nm, 117 nm, and 162 nm were determined to be 0.107, 0.250, and 1.017 mg·cm-2, respectively. The largest NPLs showed the highest activity. Simultaneously, in the Tafel plot normalized to the ESA, the specific current density corresponding to 74 nm < 117 nm < 162 nm NPLs for formaldehyde oxidation in the high overpotential region was determined. This anodic reaction activated with various NPLs could thus be the rate-determining step in ECD. Additionally, an untypical open circuit potential curve containing two mixed potentials for two period depositions--Cu deposition on Ag NPLs and Cu on the deposited Cu layer--was observed. In the intended application, conductive Cu patterns on a flexible polyimide film using Ag NPL ink of 2.5-wt% solid content were successfully fabricated by inkjet printing combined with catalyzed ECD. [ABSTRACT FROM AUTHOR]

Preparation of size-controlled gold nanoparticles is required for their use in applications. Electroless growth of gold nanoparticles using Au seeds with mean diameter of 12.5 nm and hydroquinone was performed and the growth process was analyzed. The pH dependencies of the redox potentials of hydroquinone and Au(III) ionic species were evaluated to investigate the growth mechanism of the nanoparticles in detail. Furthermore, the deposition behavior of Au in the growth solution was clarified by measuring the deposition weight of Au and the mixed potential during the growth of Au nanoparticles. Size control of Au nanoparticles was achieved by changing the concentration of Au seeds in the Au growth solution, allowing Au nanoparticles with a mean diameter of 38.7-63.5 nm to be successfully obtained. [ABSTRACT FROM AUTHOR]

Magnesium metal and its alloys are known to have excellent physical and mechanical properties suitable for a number of industrial and technological applications. Yet due to their highly reactive nature, magnesium alloys have continued to see little industrial use. This paper demonstrates an extension of the recently introduced, novel method established to deposit electroless Cu films on Mg alloys to the next step of direct electroless deposition of nickel phosphorous [Ni-P] and nickel-zinc-phosphorous [Ni-Zn-P] alloy films on polished AZ91D magnesium alloys. These reasonably adhered, quick depositing, continuous, low phosphorous, electroless coatings contain phosphorous, atomically, at, or below, 10% due to the use of an alkaline deposition bath. [ABSTRACT FROM AUTHOR]

Bath stability monitoring of electroless copper deposition has been done with different methods. A combination of UV-VIS spectra and pH measurement enabled us to determine the degradation of an electroless Cu solution. The pH of the Cu-containing solution gradually decreased as a function of time, while the UV-VIS absorbance increased. The decrease of pH is due to the consumption of OH- by the deposition reaction and the Cannizzaro reaction of glyoxilic acid. As application of these methods, the effect of the preparation sequence and bath stability was evaluated, bath break down was detected by the different methods used, and the potential for process monitoring was demonstrated. Furthermore, pH control during deposition was found to be very important to avoid defects in the electroless deposited seed layer, close to the via opening and top surface. [ABSTRACT FROM AUTHOR]

Highly uniform and monodisperse core-shell microspheres composed of a polystyrene (PS) core and a copper shell were prepared by dispersion polymerization of styrene followed by etectroless copper plating. The formation of copper shell on PS surface was confirmed by FESEM, TEM, XRD and TGA. As a result, the plating bath composition had an important influence on the morphology of PS/Cu composites. The addition of Na2EDTA and La2O3 as a complexant and a stabilizer led to the formation of a more compact copper shell on PS surface. The formation mechanism was explored by the linear sweep voltammetry method, and the different morphology might mostly result from the various nucleation rates. Tailoring of shell thickness can be achieved through altering the loading of PS in the ECP bath. Conductivity of the PS/Cu composites with a shell thickness of 195 nm is up to 2.2x 105 S/m. The PS/Cu composites may have great potential to be used as fillers of anisotropic conductive film for their uniform diameter, low density and good conductivity. [ABSTRACT FROM AUTHOR]

The effect of thiourea (TU) and saccharin (SAC) on the deposition rate, surface morphology, boron (B) content, micro-hardness, and corrosion resistance of an electroless Ni-B plating layer on AZ9ID magnesium alloy was investigated. The electroless Ni-B plating layer was characterized by scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), Vickers hardness and electrochemical techniques in 3.5 wt% NaCI aqueous solution. The results showed that TU and SAC had different effects on the morphology and a similar influence on the particle size of the plating. TU slightly decreased the B content in the coating, while SAC had no effect. The two additives reduced the Ni-B plating rate and enhanced the corrosion resistance of the coating. Appropriate amounts of the additives improved higher micro-hardness of the plating. Elements diffusion occurred between substrate and coating during heat-treatment. After heat-treatment the deposited coating layer transformed from an amorphous structure to crystalline. [ABSTRACT FROM AUTHOR]

The effect of bis-(3-sulfopropyl)-disulfide (SPS) on the void-free electroless pillar-to-pillar bonding process has been investigated. Two dome-shaped Cu pillars were joined using electroless copper deposition with the addition of a suppressor to achieve solid, compliant Cu-to-Cu bonding without high temperature or pressure. SPS was added to the electroless copper plating bath which has strong suppression to the electroless plating in order to avoid the creation of an unbonded seam between the two Cu structures being bonded. The bath suppresses the deposition of copper near the entrance of the gap between the two pillars, while allowing high deposition rate in the geometrically restricted area between the copper structures being bonded. This phenomenon is due to diffusion of SPS through the narrow gap between the pillars being bonded. At adequate concentration of SPS, the two pillars were successfully joined without any remaining seam between the joined structures, by growth of copper from the center of the gap to the outside. [ABSTRACT FROM AUTHOR]

Highly conductive silver-coated glass fiber (GF) was fabricated in an efficient and environment-friendly way. When the GF powder was immersed in dopamine solution, an adherent self-polymerized poly(dopamine) (PDA) layer was formed on the GF surface. PDA acts as both a linker between GF and silver nanoparticles and a reducing agent for reducing silver ions to metallic silver. The silver nanoparticles can be chemically bound to the catechol and amine functional groups in PDA by electroless plating using glucose as reducing agent. Chemical and physical characterizations of the silver-coated GF were carried Out by using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Four-point probe was used to study the electrical resistivity of the silver-coated glass fibers. The results indicated that the silver coated on the GF surface was compact, uniform, continuous, and in a metallic crystal state. The silver content could be well controlled from 9.5 to 24 wt% by adjusting the reduction conditions. The electrical resistivity of the silver-coated glass fibers could be as low as 1.0 mΩ cm. [ABSTRACT FROM AUTHOR]

An electrochemical monitoring method was introduced to optimize catalyzing process prior to Cu electroless deposition on a Ta/TaN barrier. It utilized the electro-oxidation of dimethylaminoborane on the Pd particles formed on the substrate after the catalyzing process. The anodic current of the dimethylaminoborane oxidation was only detected when Pd particles existed, and its peak current showed a linear dependency on the Pd particle density. It was also found that the oxidation on Pd particles was an irreversible process accompanying 3-electron transfer. Using the electrochemical method, the optimization of the catalyzing process was performed to maximize the number of Pd particles per unit area (1 cm²). After the optimization, Cu electroless deposition was performed. A minimum 18-nm-thick Cu seed layer was successfully obtained and the adhesion strength was good enough to maintain the flaking-free film even after Cu electrodeposition. [ABSTRACT FROM AUTHOR]

This study examines the possibility of employing an electroless-plated Ni(P) layer as a diffusion barrier between the Sn bonding layer and Cu bump for 3D integration applications. We bonded the samples at different bonding temperatures (200∼350°C) and probed into the bonding morphology to evaluate the effects of the addition of a Ni(P) barrier. Combination of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses revealed that the Ni(P) barrier effectively suppressed Cu diffusion while an interaction between Ni(P) and Sn consumed the barrier in a gradual manner. The samples with a Ni(P) barrier were found mechanically much more reliable than those without a barrier, owing to suppressed IMC reaction and Cu diffusion. In addition, the insertion of a Ni(P) barrier did not affect the resistance much in comparison with the samples without a barrier. [ABSTRACT FROM AUTHOR]