Electroless Deposition Of Cu Research Articles

Effect of HEDTA on the Adsorption of 2,2 Bipyridyl and 3-Mercaptobenzothiazole and Electroless Cu Deposition Rate

Surface-enhanced Raman spectroscopy (SERS) and chronoamperometry were utilized to evaluate the electroless deposition of Cu in hydroxyethylethylelenediaminetriacetic acid (HEDTA)- and tartrate-based baths containing 2,2′-bipyridyl (BP) and 2-mercaptobenzothiazole (MBT). The Cu deposition rate was shown to be faster in tartrate baths, with rates at 0.08 μm min−1 without MBT or BP but decreased to near zero with concentrations approaching 6 μM of either MBT or BP. HEDTA baths displayed a slower rate of 0.04 μm min−1 without MBT or BP. However, the addition of MBT increased the rate up to 4-fold, while BP concentration did not affect the deposition rate. SERS data showed that HEDTA adsorbs to the surface while tartrate does not. Kinetic Langmuir isotherm model fits showed a decrease in MBT and BP adsorption rate in the presence of HEDTA and showed a decrease in HEDTA adsorption upon MBT injection while BP injection did not affect the HEDTA adsorption. Competition between the complexing and the stabilizing agent is a key factor for the rate of electroless Cu deposition.

A controllable , universal, and natural supramolecular assembly coating strategy for multifunctionality textiles of antibacterial properties, UV resistance, antioxidant, and secondary reactivity

The development of multifunctional, stable, and secondarily reactive surface coatings is highly desirable, regardless of the surface structure and chemistry of the textile. However, it has remained a great challenge until now. Commonly used strategies for textile surface functionalization are limited to certain types of fibers or weak and unreliable surface bonds, as well as colored surfaces. Herein, a supramolecular assembly strategy involving phase-transited lysozyme (PTL) and tannic acid (TA) is proposed, which can be used to functionalize various textiles through simple padding and drying. This coating has been shown to withstand 50 washing cycles and 100 rubbing cycles. The PTL/TA coating not only effectively improves the antibacterial properties of textiles (with a 99% bacteriostatic rate), but also enhances UV resistance and antioxidant properties. Additionally, the PTL/TA coating can serve as a secondary reaction platform to prepare X-PTL/TA@fabrics with various functionalities. For instance, sol-gel functional finishing can be employed to achieve hydrophobic modification of fabrics. Furthermore, electroless deposition of Cu on the coating surface can impart infrared stealth and electromagnetic shielding properties to the fabric. PTL/TA coatings exhibit promising practical application prospects as a bridge between various textiles and multifunctionality.

Multi-Material Additive Manufacturing of Coreless Transformers By Aerosol Jet Printing and Electrochemical Deposition

Coreless transformers are an attractive technology for power electronics due to their light weight and the absence of a brittle magnetic core material.[1] A coreless transformer consists of a primary spiral inductor with few turns and a secondary spiral inductor with many turns stacked together. Aerosol jet printing (AJP) is an additive manufacturing technology which can be used to print metals and polymers with linewidths as narrow as 10 µm. In this work we have used a combined AJP, electroless deposition, and electrodeposition approach to fabricate multi-layer coreless flyback transformers. This combined approach makes accessible both the high-resolution patterning from AJP and the high-density, high-conductivity materials such as Cu and Ni from electrochemical deposition techniques.[2]We have designed two-layer primary and secondary inductors separated by AJP-deposited UV-curable dielectric layers. Micrographs of the primary and secondary inductors are shown in Figure 1(a) and 1(b) respectively. Electroless deposition of Cu and electrodeposition of Cu and Ni are optimized in order to minimize resistive losses and promote uniform film growth. The typical inductances measured on the 2-layer primary are 0.2 µH and the inductances measured on single layers of the secondary are on the order of 4 µH. Initial testing of the transformer for flyback voltage conversion demonstrated the capability of generating an output to input voltage ratio of >50. Comparisons of the experimentally measured inductance of the primary and secondary inductors as well as the transformer voltage ratio will be compared with simulated models. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2021-15239 A

Area-Selective Electroless Deposition of Cu for Hybrid Bonding

This paper describes the use of area-selective electroless Cu deposition for topography control of Cu-SiCN hybrid bonding pads. The electroless deposition of Cu allows one to obtain protrusions on hybrid bonding Cu pads without further polishing optimization. A recessed Cu pad after chemical mechanical polishing becomes a protrusion after electroless deposition. This indicates that the electroless Cu film was selectively deposited on Cu, without deposition on the SiCN surface. A void-free Cu-Cu bonding interface was observed after annealing at 350 °C with an electroless Cu layer at the interface. 100% electrical connection was obtained at 1.4-μm pitch where the deposition thickness was on target.

Fabrication of junction-free Cu nanowire networks via Ru-catalyzed electroless deposition and their application to transparent conducting electrodes

Over the past few years, metal nanowire networks have attracted attention as an alternative to transparent conducting oxide materials such as indium tin oxide for transparent conducting electrode applications. Recently, electrodeposition of metal on nanoscale template is widely used for formation of metal network. In the present work, junctionless Cu nanowire networks were simply fabricated on a substrate by forming a nanostructured Ru with 80 nm width as a seed layer, followed by direct electroless deposition of Cu. By controlling the density of Ru nanowires or the electroless deposition time, we readily achieve desired transmittance and sheet resistance values ranging from ∼1 kΩ sq−1 at 99% to 9 Ω sq−1 at 89%. After being transferred to flexible substrates, the nanowire networks exhibited no obvious increase in resistance during 8000 cycles of a bending test to a radius of 2.5 mm. The durability was verified by evaluation of its heating performance. The maximum temperature was greater than 180 °C at 3 V and remained constant after three repeated cycles and for 10 min. Transmission electron microscopy and x-ray diffraction studies revealed that the adhesion between the electrolessly deposited Cu and the seed Ru nanowires strongly influenced the durability of the core–shell structured nanowire-based heaters.

Laponite-Mediated Copper Metallization by Palladium Intercalation.

An alternative catalytic method was employed using the reduction of Pd ions on the surface of cetyltrimethylammonium bromide (CTAB) treated laponite to initiate the electroless plating of copper; the deposition features of the Pd nanoparticles produced were investigated in detail. Results indicated intercalation and reduction of Pd nanoparticles occurred at room temperature and involved interaction between the laponite and the cetyltrimethylammonium cationic templates. Organic species and amount on laponite were optimized to adjust silicate platelet interlayer distances and platelet organophilic properties. Intercalation of Pd nanoparticles occurred between the magnesium silicate layers of laponite and this was dependent on pre-treatment and impregnation times. As impregnation is a method of producing heterogeneous catalysts, we considered Pd nanoparticles on laponite templates could catalyze the electroless deposition of Cu to initiate metallization. Cu films fabricated on laponite templates exhibited excellent surface roughness (˜1.7 nm) and low resistivity (˜3.42 μΩ). The devised approach enabled the facile formation of a network suitable for Cu metallization without causing substrate damage and produced metal surfaces with excellent flatness and resistivity.

Testing PtCu Nanoparticles Supported on Highly Ordered Mesoporous Carbons CMK3 and CMK8 as Catalysts for Low-Temperature Fuel Cells

Pt(Cu) nanoparticles supported on CMK3 and CMK8 ordered mesoporous carbons (OMCs) have been synthesized by electroless deposition of Cu followed by galvanic exchange with Pt. The structural characterization by high-resolution transmission electron microscopy and X-ray diffraction showed the formation of Pt(Cu) nanoparticles of 4–5 nm, in which PtCu alloys with contracted fcc Pt lattice and 70–80 at.% Pt was identified. The X-ray photoelectron spectroscopy analyses indicated that the Pt(Cu) nanoparticles were mainly composed of a PtCu alloy core covered by a Pt-rich shell, in agreement with the steady cyclic voltammograms, which did not show any Cu oxidation peaks. Electroactive surface areas up to about 70 m2 gPt−1 were obtained. The onset potentials for CO oxidation and the oxygen reduction reaction were more negative and positive, respectively, as compared to Pt/C, thus indicating higher activity of these Pt(Cu) catalysts with respect to the latter. Based on the corresponding binding energies, these better activities were attributed to the favorable geometric and ligand effects of Cu on Pt, which were able to reduce the adsorption energy of the intermediates on Pt. Pt(Cu)/CMK3 showed competitive mass and specific activities, as well as better stability than Pt/C.

Effect of Al2O3 nanoparticles content and compaction temperature on properties of Al–Al2O3 coated Cu nanocomposites

This paper presents experimental investigation on the effect of Al2O3 content and compaction temperature on mechanical and wear properties of Al–Al2O3 coated Cu nanocomposites. With the aim of improving wettability and dispersion of high weight fraction of Al2O3 nanoparticles in Al matrix, Al2O3 nanoparticles were electroless coated by Cu particles. High-energy ball milling followed by hot compaction was applied to manufacture Al–Al2O3 coated Cu nanocomposites. The results showed that increasing Al2O3 nanoparticles content up to 10 wt% improved hardness and wear properties of samples compacted at 400 ᵒC, while by increasing Al2O3 content to 15 wt%, the properties were negatively affected due to the agglomeration of Al2O3 nanoparticles and the high reduction of relative density. However, well dispersion of high content of Al2O3, 15 wt%, was achieved in samples compacted at 700 MPa which improved hardness by 105% compared to pure Al. The hot compaction temperature highly influenced structural, mechanical and wear properties of compacted samples. Increasing compaction temperature, reduced crystallite size (49 nm) and increased the relative density of Al–Al2O3 coated Cu nanocomposites which improved mechanical and wear properties of the produced samples. Applying electroless deposition of Cu over Al2O3 nanoparticles followed by high-energy ball milling and hot compaction at 700 MPa is an efficient procedure for production of Al–Al2O3 coated Cu nanocomposite with relatively high Al2O3 content.

Electroless Deposition-Assisted 3D Printing of Micro Circuitries for Structural Electronics.

Three-dimensional (3D) printing is a next-generation free-form manufacturing technology for structural electronics. The realization of structural electronic devices necessitates the direct integration of electronic circuits into 3D objects. However, creating highly conductive, high-resolution patterns in 3D remains a major challenge. Here, we report on a metallic 3D printing method that incorporates electroless deposition (ELD) into the direct ink writing method. Our approach consists of two steps: (1) direct ink writing of catalyst microstructures with a functional catalyst ink containing Ag ions and (2) ELD of Cu onto the printed catalyst structures. High-quality, stable Cu 3D printing is achieved through the design of the Ag catalyst ink; hydroxypropyl cellulose is added as both a rheological modifier (printing) and dissolution inhibitor (ELD). As a result, various two-dimensional (2D) and 3D Cu micro circuitries with high conductivity (∼65% of bulk) can be directly integrated onto 3D plastic substrates without the need for high-temperature annealing. A hybrid strategy that combines ELD-assisted 3D printing and conventional fused deposition modeling enables full fabrication of structural electronic devices. This 3D printing strategy can be a low-cost and facile method for obtaining highly conductive metallic 2D and 3D microstructures in structural electronics.

Durable, Highly Electrically Conductive Cotton Fabrics with Healable Superamphiphobicity.

Electrically conductive fabrics with liquid repellency and corrosive resistance are strongly desirable for wearable displays, biomedical sensors, and so forth. In the present work, highly electrically conductive and healable superamphiphobic cotton fabrics are fabricated by a solution-dipping method that involves (NH4)2PdCl4-catalyzed electroless deposition of Cu and the subsequent deposition of a mixture of fluorinated-decyl polyhedral oligomeric silsesquioxane (F-POSS) and 1 H,1 H,2 H,2 H-perfluorooctyltriethoxysilane (POTS) on cotton fabrics. Because of their superamphiphobicity, the resulting fabrics are self-cleaning and exhibit excellent resistance against corrosive acidic and basic solutions. The as-prepared fabrics have a sheet resistance of ∼0.33 Ω·sq-1 and show excellent electromagnetic interference shielding and electrothermal heating ability. Because of the preserved F-POSS and POTS molecules, the fabrics can conveniently and repeatedly restore the loss of superamphiphobicity by applying a low voltage of 1.0 V or heating the fabrics at 135 °C to facilitate the migration of the preserved F-POSS and POTS to the surface of cotton fabrics. The integration of healable superamphiphobicity into the Cu-coated fabrics generates multiple functional cotton fabrics with excellent conductivity, electromagnetic interference shielding, self-cleaning ability, and significantly enhanced durability.

Effect of metal coating of reinforcements on the microstructure and mechanical properties of Al-Al2O3 nanocomposites

ABSTRACTThe effects of various methods of reinforcement modification on the microstructure and mechanical properties of Al–Al2O3 nanocomposites were investigated. Alumina nanoparticles were modified by electroless deposition of Cu, Ni and Co. Subsequently, aluminium matrix nanocomposites reinforced with uncoated and coated nanoparticles were produced by the stir casting method. The results of microstructural analysis showed improved wettability of coated nanoparticles in the molten aluminium alloy. Furthermore, coated nanoparticles exhibited a more desirable interface with the matrix and were homogenously distributed within it. The mechanical properties of the nanocomposites were improving significantly when coated nanoparticles were used as reinforcements. Among the reinforcement modification methods, Ni-coating was recognised as being more effective for improving the mechanical properties of Al–Al2O3 nanocomposites.

Scanning Electrochemical Microscopy versus Scanning Ion Conductance Microscopy for Surface Patterning

AbstractScanning electrochemical microscopy (SECM) offers an alternative approach for precise local electrodeposition of micro‐ and nanometer structures driven by electrochemistry. The tip generation and substrate collection mode of SECM has been applied to deposit sub‐micron palladium structures by using a Pd microelectrode. This was compared with a different approach based on scanning ion conductance microscopy (SICM). The latter was utilized also for the localized electrochemical deposition of Pd patterns using a pulled micropipette as a tip. The micropipette was filled with PdCl42− and biased versus a reference electrode placed in a NaCl solution. The application of a negative potential to the micropipette causes negatively charged ions, PdCl42−, to egress the pipette, which were electrochemically reduced on a conducting surface. The Pd patterns locally deposited by SECM and SICM were used for the local electroless deposition of Cu. Comparison between the two techniques shows that SICM is superior to SECM in terms of resolution and ease of tip preparation.

Sn-Cu Alloy Microtubes for Li-Ion Battery Anode Prepared By Electroless Plating

Graphite is generally used for the anode of Li-ion batteries. One of the disadvantages of graphite anode is its small specific charge of 372 mAh/g for lithiation and delithiation. Sn-based materials have been studied as the anode materials alternative to graphite, because Sn has relatively large specific charge of 994 mAh/g. However, the significant volume change (300% expansion) during lithiation is a serious disadvantage of Sn anode causing the pulverization of the anode.To overcome the limitation of Sn-based anode due to the large volume changes, one approach is reducing the particle size of the anode materials. In this regard, varieties of nanostructures and micro 3D architectures of Sn-based materials have been proposed to accommodate the expansion. Sn alloys with the inactive elements such as Cu have also been studied because the alloying elements are expected to buffer the volume change.We propose here the novel and facile processes to prepare the micro architectures of Sn-Cu alloys for the high performance Li-ion battery anode. Cu6Sn5 microtubes are prepared by electroless deposition of Cu and Sn on a polyethylene terephthalate (PET) nonwoven fabric, and their performances as the Li-ion battery anode are evaluated. Preparation of Sn-Cu alloy microtubesPET nonwoven fabrics were hydrophilized by dipping in an O3 saturated 1M HNO3. Pd catalysts were adsorbed on every fiber of 12 micrometers in diameter, and Cu was subsequently deposited from a conventional electroless plating bath. Sn was deposited on the Cu-coated fibers by the contact immersion processes (1). In the contact immersion processes, the Cu-coated fabric was dipped in a Sn2+–citrate solution, and was electrically contacted to metallic Sn dipped in the same solution. Sn was deposited on Cu at underpotentials, and diffused into the Cu substrate to form the intermetallic phase, Cu6Sn5, without annealing. We obtained the Cu (1500-nm thick) / Cu6Sn5 (200-nm thick) bilayer microtubes which completely coat the PET fibers as shown in Fig. 1. Charge-discharge CyclingCharge-discharge characteristics of the Sn-Cu microtube fabric anodes were evaluated in a two electrode flat type cell using a Li foil as the counter and reference electrode and a 1M LiPF6 solution in 1:1 EC/DEC as the electrolyte. Measurements were carried out at a constant current corresponding to the C-rate of 0.5 over the range of 0.001-2.0 V vs. Li/Li+.Charge-discharge capacity vs. cycle number plots showed that the capacities of the microtube anode were stable at around 850 mAh/g-Sn during the first 50 cycles. This is as high as 85% of the specific charge of Sn. The coulombic efficiencies were also high, exceeding 95%, during the 50cycles. Reference (1)Y. Fujiwara, Thin Solid Films, 425, 121 (2003). Figure 1

Glyoxylic Acid as Reducing Agent for Electroless Copper Deposition on Cobalt Liner

Electroless deposition of Cu was investigated on thin Co layer for through Si via with high aspect ratio structure. The electroless deposition bath was optimized for minimizing Co corrosion during Cu nucleation by using electrochemical analysis. Glyoxylic acid, which is known as non-toxic reducing agent for electroless Cu deposition, showed anodic oxidation on Co, which did not appear for the case of formaldehyde. Furthermore, ratio of complexing agent and Cu ion also impacted Co corrosion; free complexing agent in the electroless deposition bath accelerated corrosion of Co. The optimized electroless bath which contained glyoxylic acid as reducing agent and non-free EDTA performed in 3 μm × 50 μm TSV, the electroless deposited Cu layer could serve as a seed layer for TSV filling by electrodeposition. The electroless Cu layer was continuously deposited without missing of continuity of Co layer even close to the bottom of TSV.

Steam reforming of methanol over structured catalysts prepared by electroless deposition of Cu and Zn on anodically oxidized alumina

Steam reforming of methanol (SRM) was investigated over a series of porous structured Cu–Zn/γ-Al2O3/Al catalysts. The porous γ-Al2O3 layer was synthesized on the Al substrate through anodic oxidation in an oxalic acid solution. Cu and Zn in different molar concentrations were loaded using electroless deposition over the prepared γ-alumina support. The synthesized catalysts were characterized using the BET, XRD, SEM, and energy dispersive X-ray analysis. The Cu metal surface area was measured by the selective chemisorption of nitrous oxide. The obtained γ-Al2O3/Al (AAO) had a specific surface area of 27 m2/g, and it was observed that the Al2O3 layer contained well-developed nanopores (∼60 nm), making it ideal for use as a catalyst support. The results showed that the BET surface area of the catalyst linearly decreased with the Cu–Zn loading. The Cu metal surface area increased with increasing copper concentration in the deposition bath solution. A fixed tubular reactor was designed and fabricated to evaluate the catalytic activity of the Cu–Zn/AAO catalysts for SRM. Among the catalysts, Cu(0.06)Zn(0.06)/AAO showed 78% MeOH conversion at 350 °C. MeOH conversion linearly increased with increasing electroless deposition time from 0.5 to 10 min and appeared to plateau thereafter, indicating that 10 min was the optimal loading time.

Reaction Mechanism of Thiourea as Suppressor in Electroless Cu Deposition Process

For more precise control of the electroless deposition process, reaction mechanisms of additives should be elucidated well. Particularly, in the case of the electroless deposition of Cu, behavior of thiourea (TU), which is one of the most widely used suppressor, molecular level understanding is significant. Although analyses of TU have been reported by numbers of researchers [1,2], its suppression mechanism has not been systematically understood. In this study we attempted to elucidate suppression mechanism of TU in electroless Cu deposition with formaldehyde as a reducing agent.Since the electroless Cu deposition reaction involves both oxidation of formaldehyde and reduction of Cu2+ ion, the effect of TU on each reaction should be evaluated separately. For this, we employed “separated bath” system [3]; the bath without Cu2+ ion (oxidation bath), in which the only oxidation of formaldehyde proceeds, and the bath without formaldehyde (reduction bath), in which the only reduction of Cu2+proceeds, are connected with copper wire as shown in Fig. 1. The conditions of each bath are listed in Table 1.When TU is added only to the oxidation bath, current density steeply decreased as shown in Fig. 2 (a), indicating that TU inhibits the oxidation of formaldehyde. On the other hand, when TU is added only to the reduction bath, current density slightly increased as shown in Fig. 2 (b), indicating that TU accelerates the reduction of Cu2+, probably due to the capturing effect of TU on Cu2+around the interface [4]. Overall, TU suppresses the Cu deposition reaction by inhibiting the oxidation reaction of reducing agent.To elucidate the inhibition effect of TU on the reaction of formaldehyde, the adsorption states of TU and formaldehyde are calculated by DFT. Comparing these results, it is indicated that the adsorption energy of TU is much higher than that of formaldehyde. This shows that the adsorption of TU is much favorable on Cu substrate rather than that of formaldehyde. Hence, TU should inhibit the adsorption of formaldehyde by occupying the adsorption sites. Furthermore, from the DFT analysis, combined with SERS measurement, monomeric TU was indicated to adsorb on Cu surface via its NH2group because of the solvent effect.AcknowledgementsThis work was financially supported in part by Grant-in-Aid for Scientific Research (A) and “Development of Systems and Technology for Advanced Measurement and Analysis” program of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

Direct Cu Electrodeposition on the Ni Alloy Barrier Layer Prepared By Electroless Deposition on SiO2

The formation of barrier layer by electroless deposition (ELD) takes great interest for the next generation ULSI metallization, because ELD contains various advantages including low process cost, low process temperature, and the excellent conformality[1,2]. Especially, the research on the Ni or Co based alloy barrier layer is widely conducted as the barrier layer property of the film was superior[1-3].Some researches realized the all-wet metallization by using ELD barrier layer, however, the formation of the conformal Cu seed layer is still a big issue before the electrodeposition (ED) of Cu. The Cu seed layer formation on the ELD barrier layer usually conducted by ELD of Cu and/or the displacement reaction between Cu and barrier metal. In the point of the productivity of the device, however, the elimination of the Cu seed layer formation step would be preferred. Hence, in this study, we investigated the direct ED of Cu without Cu seed layer on the electroless NiWP barrier layer.NiWP barrier layer was formed on a Pd-activated SiO2 substrate by ELD in an acidic electrolyte. The SiO2substrate was activated by the Pd nanocolloids immobilized via the self-assembled monolayer on the surface. Prior to the direct ED of Cu, the native oxide of the NiWP barrier layer was removed by the coulometric reduction method.The linear sweep voltammetry (LSV) for the Cu reduction was investigated on the electroless NiWP barrier layer after the native oxide removal. As can be seen in Figure 1, the charge transfer limiting region of Cu deposition was separated into two stages: the Cu nucleation stage and the Cu film growth stage. However, because the resistivity of the electroless NiWP barrier layer was high, it was difficult to form a smooth and uniform Cu film by means of the one-step potentiostatic method. The low nucleation density of Cu or the non-uniform Cu deposition was problematic at low or high overpotential case, respectively (Figure 2a and 2b)[4]. On the other hand, the two-step potentiostatic method could successfully deposit the smooth and uniform Cu film, because the high overpotential induced higher nucleation of Cu and the low overpotential resulted in the smooth and uniform film growth (Figure 2c).The barrier layer property was studied using the ED Cu / ELD NiWP / SiO2 stacked specimen. The adhesion between each layer (ELD NiWP / SiO2and ED Cu / ELD NiWP) was excellent, which was evaluated by the tape test method. The electroless NiWP barrier layer could endure the 500°C and 30 min of thermal treatment. The minimal change in sheet resistance and the absence of silicide-related peaks in XRD analysis attested the thermal stability of the barrier layer. In addition, the patterned specimen covered with the electroless NiWP barrier layer was successfully filled by the direct ED of Cu with the conventional additive combination for the gap-filling. In this symposium, the direct Cu ED process on the electroless NiWP barrier layer will be addressed in detail. In addition, we will also discuss the trench filling by the proposed method.

Parameters optimization of electroless deposition of Cu on Cr-coated diamond

Electroless copper plating on diamond particles precoated with 1% Cr was carried out to evaluate the effects of various experimental parameters on coating quality and deposition rate to obtain the optimized reaction parameters. The formulated samples under optimized parameters were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectra and optical microscopy. The best parameters, where uniform and maximum coating thickness was achieved, are etching with 20% NaOH for 30 min, sensitization and activation with SnCl2 and PdCl2 for 5 and 20 min, respectively. The composition of the copper solution bath was 16 g/L CuSO4·5H2O, 35 mL/L formaldehyde (HCHO), 23 g/L KNaC4H4O6 at 60 °C, pH=13 and stirring at (350±15) r/min under ultrasonication.

Metal Assisted Synthesis of Single Crystalline Silicon Nanowires at Room Temperature for Photovoltaic Application

Synthesis of single crystalline silicon nanowires (SiNWs) array at room temperature by metal assisted chemical etching and its optical absorption measurements have been reported in this article. It has been confirmed that, SiNWs were formed uniformly on p-type silicon substrate by electroless deposition of Cu and Ag nanoparticles followed by wet chemical etching in (Hydrogen Fluoride) HF based Fe(NO3)3 solution. Synthesized SiNW structures were analyzed and investigated by Scanning Electron Microscopy (SEM) and Ultraviolet-Visible (UV-VIS) spectrophotometer. Formation of SiNWs is evident from the SEM images and morphology of the structures depends upon the concentration of chemical solution and etching time. The synthesized SiNWs have shown strong broadband optical absorption exhibited from UVspectroscopy. More than 82% absorption of incident radiation is found for Cu treated samples and a maximum of 83% absorption of incident radiation is measured for Ag synthesized samples which is considerably enhanced than that of silicon substrate as they absorbed maximum of 43% of incoming radiation only.

Copper Galvanic Replacement on Aluminum from a Choline Chloride Based Ionic Liquid: Effect of Thiourea

The deposition of copper (Cu) on aluminum (Al) is important for submicron interconnects and plating treatments of Al-based substrate. While aqueous deposition of Cu on Al is challenging on several technological and environmental problems. In this paper, we described electroless deposition of Cu onto Al surface through galvanic replacement from a simple and stable choline chloride (ChCl) based ionic liquid comprising a 1:2 stoichiometric mixture of ChCl and ethylene glycol (EG). Thermodynamic feasibility of Cu deposition by galvanic replacement on Al in ChCl-EG ionic liquid was studied by cyclic voltammetry. The effect of thiourea (TU) on the kinetics of galvanic replacement and the characterization of Cu layers were investigated by open circuit potential (OCP), electrochemical noise (ECN), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results showed that sustained deposition of Cu on Al surface was achieved in both the ChCl-EG ionic liquid solutions without and with addition of TU. The presence of TU in the ionic liquid restrained the galvanic replacement process, resulting in obtaining a compact and uniform Cu layer on Al surface.