Papers by Keyword: Electroless Deposition

Abstract: Multiple-input multiple-output (MIMO) antenna technology owes its low weight and energy-saving electronic applications to the use of polymer substrates. Applying metallization to obtain conductive substrates involves spraying untreated molds with a gel to form a temporary protective coating. The coating is then partially removed with a laser to expose areas for metallization. After that, the exposed areas are modified with a palladium-tin (Pd-Sn) colloidal catalyst to enhance the adhesion between the insulating surface and copper deposition. It’s with these three steps that the modified areas become selective to metallization. It’s observed that copper deposited incessantly at a high speed of 5 μm/hr after above treatment, and formed a dense layer with a low resistivity. The conductive patterns plated on the 3D substrate render the MIMO antenna system applicable to wireless local area network (WLAN) with two switchable frequencies, as evidenced by the simulation tests in which the antennae had ECC values below 0.2, a VSWR of 3 to 1, and a radiation efficiency around 50% at 2.4 GHz and 37% at 5.8 GHz. The electroless plating technology used above adds to a duplicable MIMO-antenna manufacturing process of low temperature and cost.

Abstract: Octahedral Cu hierarchical nanostructures were prepared by electroless deposition in aqueous solution at 80 °C. Polyvinyl pyrrolidone (PVP) was employed as the protective and structure directing agent to prevent oxidation and agglomeration of the Cu products. Addition of higher amounts of PVP (about 1.275 g) resulted in smaller but irregularly-shaped Cu nanoparticles. The Cu nanoparticles have a mean particle diameter of about 200 nm with excellent size distribution. On the other hand, Cu octahedrals were produced when 0.425 to 0.850 g PVP was used. In situ mixed potential monitoring of the solution during electroless deposition revealed that the mixed potential was more positive at larger amounts of PVP. This can be attributed to slower reduction rate due to the decrease in the activity of Cu(II) ions. Consequently, smaller Cu nanoparticles were produced.

Abstract: Cobalt (Co) nanowires were synthesized via electroless deposition in ethylene glycol under an external magnetic field then oxidized in air via thermal oxidation at 250 to 300 °C. The nanowires have lengths in the range of 10 to 14 µm while the diameter increases with oxidation temperature. This can be attributed to the partial melting of the nanowires during oxidation, resulting to sintering. The peaks in the XRD patterns show complete oxidation of Co nanowires, producing a mixture of Co₃O₄ and CoO. It was observed that Co₃O₄ and CoO peaks were more intense at 270 °C. There is a decrease in specific capacitance (F/g) with increase in scan rate due to poor electron exchange between active material electrode and electrolyte. Highest calculated specific capacitance was 339.28 F/g using nanowires oxidized at 270 °C at 1 mV/s scan rate.

Abstract: Electroless Ni-Zn-P coating with the optimal content of Ni and Zn in the alloy provides high corrosion resistance for steel. Ni-rich phase of this high hardness Ni-Zn-P alloy offers barrier protection property and sacrificial protection property is obtained from the alloy with proper content of Zn. In this work, the Ni-Zn-P coatings were prepared on steel substrates by using alkaline electroless deposition. The parameters of deposition process including complexing agent concentration, bath pH, zinc ion and nickel ion concentration were systematically studied. The microstructural morphology and elemental composition of the coatings were characterized by scanning electron microscopy. It was found that complexing agent, zinc ion and nickel ion concentrations play important role on Zn content of Ni-Zn-P alloy whereas alkalinity of the solution bath directly affects the deposition rate. The results of corrosion resistance investigated by linear polarization illustrate that the corrosion potential (E_corr) of Ni-Zn-P coatings is negatively shifted by an increase of Zn content in the alloys. From this work, E_corr of 83%Ni-11%Zn-6%P coating prepared in this system is slightly lower than steel. To achieve a higher effect of sacrificial protection for corrosion protection of steel, Ni-Zn-P with higher content of Zn should be further studied.

Abstract: NiMoB alloy films were deposited on silicon substrate by electroless deposition for diffusion barrier application in copper interconnects technology. NiMoB(40nm)/SiO₂/Si and NiMoB(20nm)/Cu (40nm)/NiMoB(40nm)/SiO₂/Si samples were prepared and annealed at temperatures ranging from 400^◦C to 600^◦C. Samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Four Point Probes (FPP) and Atomic Force Microscopy (AFM) to investigate the phases, composition, sheet resistance and surface morphology. The results showed that electroless deposited NiMoB film can be used as an effective Cu diffusion barrier layer until 500^◦C. And the failure mechanism is that NiMoB crystallized and grains grew after annealing at high temperature, a large number of Cu grains passed through NiMoB film via grain boundaries and then reacted with Si substrate and oxygen, causing the generation of highly resistive Cu₄Si and CuO.

Abstract: CoMoB film was prepared on Si substrate via electroless deposition as the diffusion barrier for ULSI-Cu metallization. Annealing experiments of CoMoB(30nm) film and CoMoB(10nm)/Cu (40nm)/CoMoB(30nm)/SiO₂/Si multi-films were carried out in the temperature range from 400^◦C to 700^◦C. Failure temperature and mechanism of Cu diffusion in CoMoB film were discussed. The composition, sheet resistance and morphology of the film were investigated by X-Ray Diffractometer (XRD), Four Point Probe (FPP) and Atomic Force Microscopy (AFM), respectively. It can be concluded that the failure temperature of CoMoB film is 600^◦C. The main reason of failure is that a large number of Cu particles passed through CoMoB grain boundary and reacted with Si substrate to generate Cu₄Si with high resistance.

Abstract: Oxidation-stable copper (Cu) nanoparticles have been successfully prepared by electroless deposition in water at 353 K. Cupric oxide (CuO) and hydrazine (N₂H₄) are employed as the Cu precursor and reducing agent, respectively. The Cu nanoparticles have uniform particle sizes with average values ranging from 37 to 43 nm. The addition of gelatin has played a vital in role in controlling the particle size, agglomeration, and oxidation of Cu nanoparticles. In the absence of gelatin, both metallic Cu and cuprous oxide (Cu₂O) are present in the sample, indicating incomplete reduction of the CuO. Pure metallic Cu nanoparticles with excellent oxidation and dispersability in water can only be formed when gelatin is employed as protective agent. At higher amounts of gelatin, the particle size of the Cu nanoparticles is reduced.

Abstract: We report a one-pot, low temperature process for the synthesis of high-aspect ratio copper nanowires in aqueous solution for 1 hr. Ethylene diamine (EDA) was utilized to promote anisotropic reduction of Cu (II) by hydrazine. Cu nanowires with mean diameters around 90 nm and lengths exceeding 50 μm were synthesized using 180 mM EDA at 60°C, giving an effective aspect ratio of about 450. Without EDA, nanoparticle growth is observed. The synthesis temperature was also significant in limiting nanoparticle formation. Decreasing the temperature resulted to 1D growth and fewer nanoparticles.

Abstract: We have investigated the magnetic properties of nanostructured Co-B alloys, that were prepared via electroless deposition. The deposition process results in the formation of a nanostructure consisting of nanotubes connected to thin films at both ends. Depending on the deposition time end-open or end-closed nanotubes can be formed. The overall nanostructure of Co-B deposit has a specific magnetization of 65.6 ± 8 JT^-1Kg^-1 (0.75 ± 0.09 μ_B per Co atom). We also investigated the anisotropy of the nanostructure by carrying out magnetic measurements with and without the top and base films. We only observed magnetic anisotropy in nanostructures with thin films, which had minimum coercivities of 557 A/m (7 Oe) and 4536 A/m (57 Oe) measured parallel and perpendicular to the nanotube axis. The nanotubes do not show any significant anisotropy with coercivities of 8753 A/m (110 Oe) and 7161 A/m (90 Oe) parallel and perpendicular to the nanotube axis.

Abstract: The electroless deposition technique was used to obtain Ni-P coatings with various phosphorus content. Machine vision method was applied as a tool for the analysis and interpretation of the data provided by electrochemical impedance spectroscopy (EIS) corrosion studies. The degree of corrosion of the coating surface could be determined by this method. The combination of both methods allows a more complete evaluation of the protective properties of the obtained coatings.