Materials Science Forum Vols. 561-565

Abstract: Behavior of the irradiation defects after annealing in electron irradiation CZ-Si has been studied by Four-Point Probe Measurement, Fourier Transform Infrared Absorption Spectrometer (FTIR) and Optical Microscope. The resistivities of irradiated silicon would decline under annealed at 750°C, it is considered that the oxygen related defects which present donor state were produced after annealed.

Abstract: The growth velocity has a significant effect on the preferred orientation of the directionally solidified Fe81Ga19 magnetostrictive alloy. Strong <100> preferred orientation was obtained for a velocity range from 10mm/h to 20mm/h. An excellent magnetostriction λ100 of 294×10-6 was achieved for the <100> oriented crystal at a pre-stress of 74.1MPa. Linear and volume magnetostrictions were investigated in the as-cast Fe81Ga19 alloys with A2 phase by measuring the change in length along the three-dimensional directions of the samples. Due to the contribution of the volume magnetostriction, the longitudinal magnetostriction increased from 27 ppm at 0.3 T to 47 ppm at 2.0 T. The volume magnetostriction can be drastically enhanced by doping Ga in Fe.

Abstract: The spheroidal graphite cast iron is widely used as a structural material in an industrial field. Possibility to be able to use by improving magnetic characteristic of spheroidal graphite as magnetic circuit material of product related to electromagnetism besides structure material. In this study, the influence that the amount of graphite precipitation , the matrix organization, and the structure gave to a magnetic characteristic was investigated in the spheroidal graphite cast iron that makes matrix ferrite by compounding C element and the Si element and heat-treatment. The graphite was completely precipitated at the heat-treatment temperature of 1173K or more, the organizatiom became a ferrite, and permeability rose. Moreover, Rough making by heat-treatment the size about the particle size of the ferrite and the appearance of the Fe-Si phase have raised permeability.

Abstract: Recently the present authors’ group found that porous silicon showed strong and stable white/white-blue light emission after successive thermal carbonization and oxidation by water vapor. This material can be considered as a price-competitive solid-state white-light source. We examined these layers by electron energy-loss spectroscopy (EELS), energy-filtering transmission electron microscopy (EFTEM). The EEL spectra indicated that the silicon skeleton in the porous layer was completely oxidized by the thermal treatment in wet argon ambient and multi-types of carbon phases were present in the 1073 K oxidized sample of stronger emission, while carbon complexes including Si and/or O were formed in the 1223 K oxidized sample of weaker light emission. EF-TEM images showed that carbon/oxygen were more uniformly distributed in the 1223 K oxidized sample. It is assumed that the strong light-emitting properties are controlled by the size and internal chemical bonding states of carbon clusters incorporated.

Abstract: Microstructure of the anisotropic Nd-Fe-B thick-film magnets has been investigated by transmission electron microscopy. Specimens of the thick-film magnets were prepared by the high-speed pulsed laser deposition method with a substrate heating system. It was revealed that the film deposited on a Ta substrate has a three-layer structure of Nd2Fe14B: The lower layer is composed of isotropic grains about 50-300 nm in diameter, the middle one has a columnar structure of 1 3m in height, and the upper one is again composed of small isotropic grains about several ten nm in diameter. The three-layer-structure is explained to result from a partial recrystallization of micro-crystalline Nd2Fe14B that are formed at the moment of deposition. In the middle layer, the c-axis of columnar grains is fairly aligned in the direction perpendicular to the substrate surface. The preferred orientation of c-axis produces the magnetic anisotropy of the thick-films.

Abstract: The actuator has widely used in CD and DVD system it have more application foreground in the future, but nonlinearity and creep exist in the actuator, which limit actuator application in high capacity, high redundancy, high transfer rate and short access time system. In this paper, we give a detail introduction on the actuator laser of optical disk high-frequency electromagnetic vibrations characteristic.

Abstract: 180nm-thick Ni33Fe67 and Ni21Fe79 films were deposited on SiO2/Si(100) substrates at 633 K by DC magnetron co-sputtering. Structural, electrical and magnetic properties of the films were investigated using X-ray diffraction, field emission scanning electron microscopy, a four-point probe technique and an alternating gradient magnetometer. The Ni21Fe79 film has a single bcc structure whereas the Ni33Fe67 film is a fcc-bcc mixed phase. The films grow with granular grains. The grain shape of the Ni21Fe79 film is triangular and rectangular. The Ni33Fe67 film consists of irregular shaped grains and a few large triangular grains. The grain size of the Ni21Fe79 film is larger than that of the Ni33Fe67 film. The resistivities of the Ni21Fe79 and Ni33Fe67 films are 1.82×10-63m and 1.09×10-63m. The saturation magnetization of the Ni21Fe79 and Ni33Fe67 films are 1.09×106 A/m and 1.02×106 A/m. The coercivity of the Ni21Fe79 and Ni33Fe67 films are 2.06×104 A/m and 8.84×103 A/m , respectively.

Abstract: The deposition of a well adherent diamond film on titanium and its alloys is always complicated due to the different thermal expansion coefficients of the two materials, the complex nature of the interlayer formed during diamond deposition, and the difficulty in achieving very high nucleation density. In this work well-adherent and smooth nano-crystalline diamond film was successfully deposited on pure titanium substrate by microwave plasma assisted chemical vapor deposition (MWPCVD) method in CH4/H2 environment. It is found that the average grain size was less than 20 nm with a surface roughness value as low as 28nm. Of particular interest in this study was the exceptional adhesion of approximately 2μm-thick diamond film to the metal substrate as observed by indentation testing up to 150 kg load. Experimental results on growth mechanism and obtaining good adhesion are discussed.

Abstract: Metal-induced lateral crystallization (MILC) of patterned amorphous silicon(a-Si) thin film using Ni as a catalyst has been investigated. Ni-MILC grains are based on the growth of needle-like crystals due to the migration of NiSi2 precipitates, which located at the crystalline front, along the <111> directions. In the case where the needle-like crystallites collided at the a-Si pattern edge, not only “turn” or “branch” of the needle-like crystallites toward one of the possible <111> directions but also the growth along the pattern edge were observed. By limiting the growth area, the competitive growth of dendrite crystals that originated in needle-like crystallites was found to appear. This phenomenon resulted in the orientation alignment of MILC crystals in a wide area. Besides, the grain-filtering of MILC crystals was found to be possible by narrowing the pattern width.

Abstract: Chain-like Carbon Nano-tubes films have been synthesized by microwave plasma enhanced chemical vapor deposition (MWPECVD). The titanium-coated ceramic substrate was placed in a stainless steel reaction chamber of MPCVD system. Prior to deposition, The substrates were grinded with SiO2 powder with Fe dopant . The mixture gas of methane (CH4) and hydrogen (H2) was introduced into the chamber. The flow rates of CH4/H2 were controlled at 14/100 sccm by mass flower, respectively. The total pressure in the chamber was kept at 6.2kPa during the deposition. The microwave power of 1700w, worked at a frequency of 2450Mhz, was applied during deposition. The deposition time was only 1minute. The nano-structure of the deposited films was analyzed by SEM, TEM and Raman spectroscopy. The chain-like nano-tubes randomly distributed on the substrates. The nano-tubes are multi-wall with diameter of about 60 nm. The field electron emission characteristics of the Chain-like Carbon Nano-tubes films were measured under the vacuum of 10-5Pa. The low turn-on field of 0.74V/μm and emission current density of 8.5mA/cm2 at electric field 2.9V//μm were obtained. The mechanism of its field emission properties was also discussed.