Mechanisms for potential oscillations and synchronizing self-organized formation of ordered dendrite structures, which is an important example of morphogenesis in Laplacian fields, were studied using Sn, Zn, Cu, and Pb electrodeposition. Electron backscattering diffraction (EBSD) experiments showed that Sn latticework as a typical example of the ordered dendrite structures grew in an epitaxial mode in particular directions from the Sn electrode surface. In situ optical and phase-contrast microscopic inspection showed that the Sn latticework growth as well as the concentration profile for deposited Sn(II) ions near the growing front oscillated in synchronization with the potential oscillation, which led to formation of a highly ordered Sn latticework structure. Similar behavior was observed in other electrodeposition systems. On the basis of these results, a general mechanism for the potential oscillations and synchronized formation of the ordered dendrite structures was proposed, in which autocatalytic crystal growth, passivation in flat surfaces of dendrites, and depletion of deposited metal ions in the electrolyte near and inside the dendrites played the key roles. Numerical calculations by use of a modified coupled map lattice (CML) model confirmed the validity of the mechanism. The clarification of the general mechanism has enabled us to classify all the oscillatory dendrite growth, including reported ones by other research groups, into three types (type-I, type-II, and type-III), which will serve for preparation of designed and controlled micro-and nanostructures at solid surfaces.

We investigate the effects of pulse duration on the dynamics of the nascent plasma and bubble induced by laser ablation in water. To examine the relationship between the nascent plasma and the bubble without disturbed by shot-to-shot fluctuation, we observe the images of the plasma and the bubble simultaneously by using two intensified charge coupled device detectors. We successfully observe the images of the plasma and bubble during the pulsed-irradiation, when the bubble size is as small as 20 lm. The light-emitting region of the plasma during the laser irradiation seems to exceed the bubble boundary in the case of the short-pulse (30-ns pulse) irradiation, while the size of the plasma is significantly smaller than that of the bubble in the case of the long-pulse (100-ns pulse) irradiation. The results suggest that the extent of the plasma quenching in the initial stage significantly depends on the pulse duration. Also, we investigate how the plasma-bubble relationship in the very early stage affects the shape of the atomic spectral lines observed at the later delay time of 600 ns. The present work gives important information to obtain high quality spectra in the application of underwater laser-induced breakdown spectroscopy, as well as to clarify the mechanism of liquid-phase laser ablation. V C 2015 AIP Publishing LLC.

The electrodeposition of noble metals, i.e., platinum, palladium, and gold, into macroporous p-type silicon was examined. For platinum and palladium, the electrodeposition proceeded preferentially from the pore bottom to the opening when sodium chloride was used as a supporting electrolyte. When sodium sulfate was used as a supporting electrolyte, the electrodeposition mainly proceeded at pore openings, leading to plugging. For gold electrodeposition, a condition for achieving pore filling from the bottom was not found in either the NaCl or Na 2 SO 4 solutions. Pore depth was another key factor to achieve continuous filling by electrodeposition. As the depth of pores became deeper, the electrodeposition proceeded preferentially from the bottom. The effect of mass transfer in pores was also investigated by changing the concentration of metal ions and applied potential.