Toshiro Endo

Deviations from Matthiessen's Rule of the Electrical Resistivity of Dislocations in Aluminum

The electrical resistivities have been measured in temperature range from 4.2 K to 300 K on both deformed and quenched aluminum, and the deviations from Matthiessens rule have been observed in both the resistivity of dislocations and of the faulted loops formed by quenched-in vacancies. The deviations show comparatively similar behavior as the whole, but in detail show somewhat different profile. The results were compared with data published by the other investigators. It is concluded that the origin of the deviation for the dislocation resistivity comes from the anisotropy in scattering mechanism. Furthermore the specific electrical resistivity of dislocation and stacking fault in aluminum were estimated as 1.2×10 -19 ohm-cm 3 and 3.7×10 -13 ohm-cm 2 , respectively.

Evaluation of surface and subsurface cracks on nano-scale machined brittle materials by scanning force microscope and scanning laser microscope

Nano-scale machining by ultra precision grinding and cutting, known as ductile mode machining, has the potential of overcoming limitations of conventional machining technology. In this study, the nano-scale layers of single crystal silicon and glass surface were machined by a sharply pointed diamond tool, and the subsurface cracks as well as the surface cracks were observed by a scanning force microscope and a scanning laser microscope. The transition point determined by the subsurface cracks is found to be shallower than that by the surface cracks. Therefore the evaluation of the subsurface cracks is important especially in finish machining.

Effects of an external magnetic field on the sedimentation of activated sludge

By applying an external magnetic field (800–3000 G, 0.08–0.30 T) using permanent magnets to the aeration vessel of an activated sludge culture, the sedimentation of activated sludge was enhanced and chemical oxygen demand (COD) removal was also improved in an indoor continuous culture system. Adding a small amount of iron(III) chloride (FeCl3, less than 0.1%, w/v) stimulated these enhancements. The possibility was suggested that the small amount of molecular iron incorporated into the activated sludge stimulated the flocculation and sedimentation by external magnetization.

Evaluation of surface and subsurface cracks in nanoscale-machined single-crystal silicon by scanning force microscope and scanning laser microscope

Abstract Studies of nanoscale machining of brittle materials, such as silicon, have come into prominence in recent years. Material removal with plastic deformation, known as ductile mode machining, has been achieved by a very small depth of cut. When surface cracks occurred with increasing cut depth, the machining has been commonly considered to be of brittle mode. In the present study, the ductile–brittle transition point in the nanoscale machining of single-crystal silicon was examined by the observations not only on the surface cracks but also on the subsurface cracks. A scanning force microscope was used to measure the depth of the grooves and to observe the surface cracks. The distance from the surfaces to the deepest point of the subsurface cracks on obliquely sectioned and then etched surfaces were measured by a scanning laser microscope. The transition point determined by the subsurface cracks was found to occur at a shallower depth of cut compared with the transition point from the surface cracks. Therefore, evaluation of subsurface cracks is important especially in the finish shape of machining.

Purity-dependent structures of Al nanoclusters on HOPG observed by STM

Abstract Nanoclusters with a diameter of 2–10 nm were deposited from highly pure Al and Al–50%Cu targets onto highly oriented pyrolitic graphite (HOPG) by pulsed laser ablation. The structures and atomic configurations of these nanoclusters were then investigated with atomic resolution using a scanning tunneling microscope. On the pure Al nanoclusters, hexagonal two-dimensional configurations were found over a large area around a three-dimensional nanocluster. These two-dimensional structures were oriented at 30° to the graphite lattice and the atomic distance was estimated to be 0.424 nm. On the other hand, two-dimensional atomic configurations were not observed around the Al–50%Cu nanoclusters and the atomic distance was almost the same as that of highly oriented pyrolytic graphite visible in the STM. Thus, the initial growth and structures were completely different between the two materials.

Deviations from Matthiessen's Rule of the Electrical Resistivity Due to Dislocations in Gold

The electrical resistivity due to dislocations in gold has been measured in the temperature range between liquid helium temperature and 300 K. The deviation from Matthiessens rule (DMR) of the dislocation resistivity is different from that of the impurity resistivity in the temperature dependence and the residual resistivity dependence. DMR of the dislocation resistivity cannot be explained by the mechanism due to an anisotropic electron distribution function. Other two mechanisms due to phonon localized modes associated with dislocations and to electron levels localized near dislocations, are considered. In conclusion DMR of the dislocation resistivity is explained fairly well by a model of electron localized levels associated with dislocations.

Fabrication of transition metal nitride films using a shock wave plasma

Abstract Thin films (about 100 nm) of NbN, MoN and (MoZr)N are formed on a fused quartz substrate by the shock wave deposition method. The highest temperatures Tco for the onset of the superconductivity transition are 11 K and 9.2 K for NbN and MoN respectively. The values of Tco are higher for the films formed on the substrates placed vertically with respect to the flow direction of the shock wave plasma than for those formed on substrates inclined to the flow. However, the latter have a more homogeneous structure and a sharper superconductivity transition.

Formation of thin films by shock wave deposition method

Abstract A T-shaped electromagnetic shock tube was used to deposit thin films of NbN and MoN on fused quartz substrates at room temperature. Deposition of NbN was carried out with Nb as the electrode material, niobium pellets were placed between the electrodes, and the initial pressure was 400 Pa in an N 2 H 2 mixture. Examination by XMA and ESCA showed that the thin film is composed mainly of NbN and is 50–60 nm thick. The nitrogen concentration ranged from 10% to 20%. In the case of MoN the thickness was about 50 nm for two plasma shots and 200 nm for eight plasma shots. All of the films exhibited the superconductivity transition.