The effects of oxide film on diamond deposition on Cr substrates oxidized at high temperature in air or at room temperature in nitric acid were studied using microwave plasma CVD. Diamond is effectively deposited when oxide film forms on the substrate. Deposited diamond density increased markedly, making diamond film when chemically passive film was formed on the substrate using nitric acid. Surface roughening was also effective in depositing diamond film.
Zn underpotential deposition with iron-group metals was studied using a Cu substrate in sulfate or chloride baths containing a small amount of Zn2+ ions at 5 to 80°C under potentiostatic conditions. Underpotential deposition occurs only in the presence of iron-group metals and is facilitated when conditions permit decreased inherent deposition overpotential of iron-group metals such as high temperature and Cl- additive. This is similar to induced alloy deposition, in which the properties of iron-group metals in a metallic state play an important role. This is cleary different, however, from induced because Zn deposition occurs at more noble potentials than its equilibrium. Iron-group metal properties in a metallic state appear responsible for Zn underpotential deposition, although the detailed mechanism is yet unclear. If the codepositing iron-group metal consistently reduces the activity coefficient of Zn deposited on the progressively formed cathode surface, the large amount of underpotential deposition is explainable thermodynamically.
A Co-Zn alloy deposit was obtained from ambient temperature molten salt electrolyte CoCl2-ZnCl2-EMIC. The Co content in the Co-Zn alloy deposit was continuously controlled from 0 to 100wt% by controlling the bath composition and current density. Co-Zn alloy deposit morphology was significantly improved by EMIC. Moreover, the bath temperature could be decreased from 130 to 80°C. The Co-Zn alloy deposit crystal structure changes from the Zn binary phase and intermetallic compound Co5Zn21 to the Co binary phase and the intermetallic corresponding compound as a function of Co content in the deposit. An amorphous deposit of Co-Zn alloy is obtained from this molten electrolyte.
Fabrication of fine pattern on an aluminum surface with pulsed YAG laser irradiation and subsequent nickel plating has been reported in two consecutive papers. The first paper studies anodic oxide film removal from aluminum by laser irradiation. Aluminum specimens covered with porous anodic oxide films were irradiated with one YAG laser pulse in air and in Ni2+ ion solutions to examine the effect of laser power, P, defocusing distance, Δx, and irradiation atmosphere on the size of film removed area. Anodic oxide films were thoroughly removed by laser irradiation at P>2mW in both air and a solution, when the specimen was placed near the focal plane of the laser beam. The size of film removed area increased with increasing P and showed a minimum on the focal plane (Δx=0), indicating 40-300μm diameter, larger in solution than in air. Oxide film removal by laser irradiation is discussed, focusing on laser ablation of the metal substrate.
Fabrication of fine pattern on an aluminum surface with pulsed YAG laser irradiation and subsequent nickel plating has been reported in two consecutive papers. The second paper studies nickel deposition on aluminum irradiated with a pulsed YAG laser, and pattern fabrication with nickel deposition. Aluminum specimens covered with porous anodic oxide film were irradiated with a pulsed YAG laser in air and in Ni2+ ion solutions using a three dimensional stage controlled by computer, and then nickel was electrodeposited and studied potentiostatically as functions of cathode potential, Ec, Ni2+ ion concentration, CNi, and bath temperature, T. Nickel was deposited only at the laser-irradiated area at potentials more negative than -0.8V (vs. sat. -AgCl/Ag), and deposition speeded up at higher CNi, T and more negative Ec. The current efficiency for nickel deposition was 95% between -1.10 and -1.40V. During cathodic polarization, cathodic current, ic, increased with time, tc, to reach a steady value at tc<1min for specimens laser-irradiated in the solution, whereas a longer period was needed to reach the steady value for the specimen irradiated in air. This suggests that thermal oxide films formed after anodic oxide film removal by laser irradiation in air inhibit nickel nuclei formation in the initial plating. The Hokkaido University Symbol 7mm in size was drawn on aluminum with nickel plating lines with different widths between 50 and 200μm.