Sub-micrometer-sized or micrometer-sized nickel oxide tubes were prepared using combining electrospinning technique and electroless plating method. A polymer (poly(methyl methacrylate, PMMA) or poly(vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP solution with palladium chloride was used as a spinning solution for electrospinning process. The spun fibers were immersed into the electroless nickel-phosphate (Ni-P) plating bath. The resultant fibers were coated with Ni-P layers. To remove the polymer fibers as a mold, the plated fibers were heated at 400−650 °C for 2 or 4 hr. Formation of sub-micrometer-sized or micrometer-sized nickel oxide tubes was confirmed through the SEM observation, EDX analysis, and X-ray diffraction measurements of heat-treated fibers. Heat treatment of the Ni-P layer on the polymer fibers also decreased the phosphorus content of the Ni layer. The average size of the nickel oxide tubes was 4.8 μm (outside diameter, O. D.), standard deviation (σ) = 0.81 μm and 2.5 μm (inside diameter, I. D.), σ = 0.43 μm prepared from PMMA fibers, and 0.7 μm (O.D.), σ = 0.17 μm and 0.3 μm (I.D.), σ = 0.025 μm from PVDF-HFP fibers.
Diamond synthesis on fine metal wire was performed effectively using hot filament chemical vapor deposition (CVD). Diamond deposition is difficult when using wire as a substrate because the substrate overheats easily. Touching the substrate directly with a cooling board is effective in such cases, but that technique is inapplicable in cases having only one wire. Another technique is to keep the substrate away from the heat source filament, thereby maintaining an ideal substrate temperature. However, the greater the distance between the filament and substrate, the lower the deposition rate would be. This study investigated a mode of indirect cooling for diamond deposition that does not lower the deposition rate. Results show that diamond on the wire substrate was deposited at a suitable temperature (900-1000 °C) by indirect cooling without keeping the filament away. The filament was hot enough that atomic hydrogen was generated. A diamond deposition rate of approximately 10 μm/h was attained.
The electrochemical behavior of Al-Si alloy films in zincate solution was investigated to elucidate the effects of zincate pretreatment on the Zn morphology and subsequent electroless NiP deposition, which is used for under bump metallization (UBM) in integrated circuit (IC) chip packaging. To investigate the electrochemical behavior of the Al-Si films during the zincate pretreatment, the immersion potential and the surface morphology during Zn and NiP deposition were evaluated using Al-Si electrodes that had been fabricated onto two types of Si substrates with different specific resistances. A heterogeneous point was observed for samples fabricated onto Si substrates with high specific resistance (45-95 Ωm), but no such point was observed on samples fabricated onto Si substrates with low specific resistance (0.00001-0.00002 Ωm). This result suggests that the morphology of the deposits was affected considerably by the specific resistance of the Si substrate.
Aluminum was anodized in an oxalic acid bath using AC and DC hybrid electrolysis at a frequency of 0.1-1000 Hz and with DC galvanostatic electrolysis. Palladium was electrodeposited as a catalyst into pores of the anodized films using AC potentiostatic electrolysis. Electroplating was prepared continuously on anodized films of aluminum. Then the anodized film was dissolved in 5 mol dm−3 NaOH aqueous solution at room temperature to obtain nickel nanopillar aggregate (about 50-90 nm diameter). Results of SEM evaluation showed that the pore diameter and number (structure) of anodized films were governed by the impressed frequency. The frequency and the pore diameter showed an inverse relation. In addition, nickel nanopillars were prepared from an anodized film template. Results show that the pillar diameter accorded with the pore diameter of the anodized film.
Three-dimensional microfabrication is an important process for fabricating microelectromechanical systems (MEMS) and optics. This paper describes reactive ion etching of quartz glass using three-dimensional aluminum masks. Aluminum masks were fabricated using photolithography, anodization, and chemical etching, with the mask shape controlled by anodization and chemical etching conditions. By changing the photoresist mask patterns, quadrangular pyramids and cones were fabricated on quartz substrates using the aluminum masks. Etching characteristics of quartz substrates were developed using CHF3 gas in a planar type plasma reactor. When the process pressure was increased, the etching rate of quartz increased and that of aluminum mask decreased. Based on these results, we increased the selectivity of the quartz/aluminum mask from 10 to 37 by adjusting the pressure. Quadrangular pyramids and cones were fabricated on quartz substrates using this method, which was demonstrated as effective for fabrication of three-dimensional microstructures on quartz substrates.