Papers by Author: Kazuo Furuya

Abstract: Electron beam induced-deposition (EBID) is a promising technique for fabricating nanometer-sized structures in a position- and size-controlled manner. The resolution of EBID is now reaching down to subnanometers. However, the deposits obtained by EBID contain a large amount of carbon. Thus, carbon reduction techniques are needed. In this study, nanostructures, such as nanowires, were fabricated by EBID using an iron pentacarbonyl precursor. Several techniques to reduce carbon were applied, including post-deposition heat-treatments and the modification of precursor. It was found that the post-deposition heat-treatment in air resulted in a formation of Fe2O3, and that carbon-free Fe3O4 was formed by mixing a small amount of water vapor in the iron pentacarbonyl precursor.

Abstract: SrTiO3 crystals were implanted with 100 keV xenon (Xe+) ions at 673 or 1073 K up to 2.0 × 1020 ions m−2. Defect clusters formed in the ion-implanted samples were investigated with conventional and high-resolution transmission electron microscopy. Nanometer-sized clusters were formed in the samples. The clusters grew large in size after post-implantation annealing and with increasing the implantation dose. The clusters were faceted with {100}, or {110} of SrTiO3. Though the nano-sized clusters were expected to contain Xe atoms, they were not in crystalline state. The results suggest that even if the clusters contain Xe atoms, they also contain other point defects such as vacancies.

Abstract: Electron beam induced deposition (EBID) was carried out with gas introduction systems attached to field emission scanning electron microscope (FE-SEM). Using iron carbonyl and ferrocene, three dimensional (3-D) antenna structures were fabricated in the range of 30-50 nm in diameter and 500-1000 nm in size. Post-deposition annealing of iron nanostructures resulted in the formation of crystalline alpha-iron and iron carbide phases. The iron concentration was controlled by the partial pressure of iron carbonyl and ferrocene. Electron holography observation with field emission transmission electron microscopy (FE-TEM) revealed that the remanent magnetic flux density Br of the nanostructures also depends on the iron concentration.

Abstract: Lap joining of A6111 alloy and steel (SPCC: Steel Plate Cold-rolled C) plates was performed using a defocused YAG laser beam. A detailed investigation was performed on the intermetallic compound (IMC) layer formed at the weld interface. Two representative joints fabricated under different welding conditions were selected and the effect of the welding conditions on the kind and morphology of the IMC was investigated using a transmission electron microscope (TEM). An electron diffraction pattern method was used to identify IMC. It was found that the morphology and kind of IMC formed at the weld interface were strongly affected by the welding conditions, in particular, by the amount of heat input during welding. The thickness of the IMC layer formed at the weld interface was about 1 μm and the average grain size of the IMC in the layer was less than 300 nm when the joining was carried out with a small amount of heat input. The IMC layer was composed of Fe3Al, FeAl, Al2Fe, Al5Fe2 and Al13Fe4 in this case. However, the thickness of the IMC layer was around 6 μm when the joining was carried out under high heat input conditions. In this case, the IMC layer was composed of coarse Al5Fe2 (5 μm) and Al13Fe4 (1 μm). Therefore, it is considered that the reduced bonding strength of the joint with a thick IMC layer is due not only to the overall morphology of the IMC layer but also to the formation of coarse Al-rich IMCs in the layer.

Abstract: Nanometre-sized structures were fabricated by electron beam-induced deposition in a scanning transmission electron microscope. A small amount of metal-organic gases, W(CO)6 and dimethyl acetylacetonato gold, were introduced near a substrate in the chamber of the microscope. The gas was decomposed by the irradiation of focused electron beams and nanometre-sized deposits containing W or Au were produced. Moving the beam position enables us to produce structures with a variety of shapes. High-resolution electron microscopy observation revealed that the structures consisted of nano-crystalline and amorphous parts.

Abstract: Nanometer-sized W-dendritic form structure was fabricated with electron-beam-induced deposition (EBID) in a 200 kV transmission electron microscope. The as-prepared nanodendrites are composed of W-nanocrystals and amorphous. The as-prepared nanodendrites were then irradiated with 1 MeV electron beam in a high voltage transmission electron microscope. The effect of the irradiation is investigated. The irradiation transformed effectively almost all the amorphous part to crystalline state. Morphology of the nanodendrite also changes. The irradiation induced crystallization and morphology change are discussed.