Taiko Motoi

Multiwalled carbon nanotubes growth in anodic alumina nanoholes

Carbon nanotubes (CNTs), standing perpendicularly to a substrate with an electrode, were fabricated by thermal catalytic decomposition of ethylene from Co particles electrochemically embedded at the bottom of anodic alumina nanoholes. The thermal durability of the alumina nanoholes for the CNTs growth process was achieved by using Nb as an underlying electrode. The CNTs were electrically connected to the electrode through the conductive paths, which were formed at the bottom of alumina nanoholes by Nb ion migration from the underlying electrode during anodization.

Template-Assisted Growth of Nanowires Using Novel Nanoporous Films Fabricated by Inorganic Nano Phase Separation

Ultrahigh pore density nanoporous films with a pore diameter of less than 10nm and a pore density exceeding 10 16 pores/m 2 were developed. Nano phase separation of a eutectic Al-Si system was used for the fabrication of these nanoporous films. Co-sputtered AlSi films form Al nano-cylinders, perpendicular to the substrate and parallel to each other, embedded in an amorphous Si matrix during film growth due to phase separation. Removal of the Al nano-cylinders from the co-sputtered AlSi films by chemical etching gives us ultrahigh pore density nanoporous films. The nanoporous films consist of mainly oxidized silicon. Depending on the film compositions and the film preparation conditions, such as RF power and the deposition temperature, the average pore diameter can be varied systematically from less than 5nm to 13nm with the pore density from 10 15 to exceeding 10 16 pores/m 2 . Furthermore we have demonstrated a template-assisted growth of ultrahigh-density Ni nanowire arrays with an aspect ratio of ∼100 in the nanoporous films by electrodeposition. The fabrication method for nanowire arrays using the nanoporous films is quite simple and promising for the fabrication of nanostructured devices.

Effect of metal cluster ions on the low-temperature growth of YBa2Cu3Oy thin films

Abstract Using the reactive ionized cluster beam method, the roles of Y, BaO x , and Cu clusters in YBa 2 Cu 3 O y (YBCO) thin-film growth are investigated. This method utilizes ionized and accelerated Y, BaO x , and Cu clusters consisting of loosely coupled aggregates of 10 2 –10 3 atoms. It is found that, at substrate temperatures below 400°C, each ionized cluster has a different effect on the formation of YBCO. Namely, ionized and accelerated Cu and BaO x clusters with an average energy of less than approximately 2.0 eV significantly promote the oxidation of the YBCO films. In particular, the use of ionized BaO x clusters facilitates crystal growth. On the other hand, ionized Y clusters exhibit an obviously negative effect on YBCO growth. These results suggest that it may be difficult to obtain completely ortho-I films in situ at substrate temperatures below 400°C because of the trade-off for the effect of ionized Y clusters and the other two ones. At temperatures above 500°C, there is no significant observable difference between the films grown by this method and those grown using a conventional method. As a result, it seems that, at higher temperatures, YBCO film growth is dominated by the thermal energy supplied from a heated substrate.