Cost of silicon carbide (SiC) wafer has been improved owing to the development of larger and higher quality wafer technologies, while the process stays long and complicated. In this paper, we propose a novel short process of ion implantation and provide the fabrication model SiC schottky barrier diodes (SiC-SBDs) devices. Currently common mask layer of ion implantation employs high heat resistant materials such as metal oxides. Because the ion is implanted to SiC wafer at high temperature between 300 °C and 800 °C due to avoid the damage of SiC crystal structure. The process using oxide layer tends to became long and complicated. On the other hand, our proposal process uses a heat resistant photoresist material as the mask instead of the oxide layer. The heat resistant photoresist is applied to newly developed SP-D1000 produced by Toray Industries, Inc.. We demonstrated to fabricate model SiC-SBDs devices based on our proposal process with SP-D1000 and confirmed the device working as same as a current process.

SiC power module with low loss and high reliability was developed by utilizing IEMOSFET and SBD. The IEMOSFET is the SiC MOSFET with high channel mobility in which the channel region is the p-type carbon-face epitaxial layer with low acceptor concentration. Elemental technologies for the high channel mobility and the high reliability of the gate oxide have been developed to realize the excellent characteristics by the IEMOSFET. The SBD was designed so as to minimize the forward voltage drops and the reverse leakage current. For the fabrication of these SiC power devices, the mass production technology such as gate oxidation, ion implantation and following activation annealing have been also developed.

To make the highly doped layer for Ohmic contact without using the ion implantation, the phosphorus doping by the epitaxial growth using phosphine (PH 3 ) was conducted. The crystal face and C/Si ratio dependence of phosphorus doping were investigated. The highest doping concentration was obtained on off-axis (000-1) face and the lowest on off-axis (0001) face. The doping level of (11–20) face was located between that of off-axis (0001) and (000-1) faces. As the C/Si ratio was increased from 0.5 to 2.5, the doping concentration increased on (11–20) and off-axis (000-1) faces. The results on off-axis (0001) face showed the unclear C/Si ratio dependence. On (000-1) face, the phosphorus doping of 2 × 10 18 cm −3 was obtained by increasing PH 3 flow rate. The roughness, growth rate, and surface morphology of the high phosphorus doped epilayer were investigated.

In this study, we investigated surface features formed by molten KOH etching of (000-1) substrates and epilayers, using scanning electron microscopy (SEM) and cross-sectional transmission electron microscopy (TEM). We found the surface features formed on (000-1) are protrusions, in contrast to well-known dimples on (0001).

The fine-grained rolling steels NFG600 and the conventional usual rolling steels SM490 were processed by sand paper polishing and mechanical grinding to compare the residual stress generated after processing. The average grain size of NFG600 and SM490 is 3 mu m and 15 mu m respectively. Therefore improvement of mechanical properties for such fine-grained steels is expected, it is important to understand the residual stress state of new fine-grained materials with processing. In this study, multi axial stresses of two kinds of specimens after polishing and grinding were measured by three kinds of analysis methods including cos-psi method. As a result, as for sigma-33, the stress of NFG was compression, though that of SM490 was tension.

The transformation of 4H-SiC etching shapes by high-temperature annealing was investigated. Although the opening of the etching mask was circular, the resulting etched shape was a hexagon, dodecagon, or rounded polygon with more edges, depending on the diameter. A hexagon was transformed into a dodecagon following high-temperature annealing, and a dodecagon was transformed into a rounded polygon.

Microstructures and mechanical properties of ultra fine-grained low carbon steels fabricated by equal channel angular pressing (ECAP) were investigated. Several specimens statically annealed for 5 hours at temperatures of 773-873K were studied simultaneously. Electron back-scattering diffraction (EBSD) measurements were carried out for microstructure observation. Differential scanning calorimeter (DSC) curves were obtained for studying the thermal stability of specimens. The initial grain size of ∼10μm in the ferrite-pearlite steel was refined to ∼0.2μm by 4 passes of ECAP. The tensile strength of the as-ECAPed specimen was around 2 times higher than that of the initial normalized specimen, although the ductility decreased by half after the process. At annealing temperature of 773-823K, tensile strength and yield stress decreased as the average grain size of each specimen increased. However the grain growth by annealing was not significant. At annealing temperature of 873K, the nonuniform grain growth occurred suddenly, and as a result the tensile strength decreased. On the Hall-Petch relation diagram, the gradient of the diagram over the average grain size of 1mm was slightly different from that of under 1μm. In addition, the nonuniform radical grain growth at the temperature of 873K was in accord with the appearance of the exothermic peak in the DSC curves. The accumulation of the local strain in the 823K-annealed specimen was investigated by the kernel average misorientation (KAM) approach using EBSD, and it is suggested that accumulation of the local strain in the 823K-annealed specimen is one of the causes of the nonuniform radical grain growth at the temperature of 873K.

In the present study, ultra fine-grained low carbon steel samples were processed by equal channel angular pressing (ECAP). Mechanical properties of the specimens annealed statically at several temperatures were evaluated by tensile and hardness test. In addition, grain sizes of the specimens were measured by SEM-electron back scattering pattern (SEM-EBSP) and X-ray diffraction analysis. Differential scanning calorimetry (DSC) measurement also evaluated thermal reactions in anneal process of the specimen. As a result, the grain size was changed at the temperature between 550oC and 600oC drastically and the tensile strength also became lower at the same temperature. The relation between yield stress and averaged grain diameter of specimens obeyed the Hall-Petch relation except the normalized specimen. Behavior of grain growth and recovery in structural observation by EBSP corresponded to reaction signal of the DSC curve.

We investigated transformation of 4H-SiC etching shapes by high temperature annealing. Although the etching mask was circular, the etched shape resulted in a hexagon, dodecagon, or octadecagon, depending on the etching area size. A hexagon was transformed into a dodecagon along with the high temperature annealing, and a dodecagon was transformed into an octadecagon.Hexagon as well as dodecagon designed with different edge directions undergo different transformation by the annealing, owing to common preference of crystallographic faces. An edge corresponding to one of the {1-10x} faces appears as a straight line and seems most preferred. Edges corresponding to the {11-2x} faces also appear in a curvy feature, suggesting to be second most preferred. Faceted structures (bunching) were observed clearly on the {1-10x} faces but faintly on the {11-2x} faces. Therefore, it is necessary to design the shapes and their directions in an actual device in consideration of the transformation by annealing.

The additional cold rolling and the aging process were applied to Cu-0.85Cr-0.07Zr alloy sheets processed by ARB, and mechanical properties and structural information were investigated for the purpose of further improvement of the mechanical properties and the electrical conductivity. From the results of the tensile test and the measurement of electrical conductivity, ARB/aged/CR was most appropriate processing in order to achieve technical advantages. The high tensile strength of 745 MPa and the high electrical conductivity of 68 %IACS were obtained simultaneously. In addition, the improvement of incomplete boundaries generated during ARB processing was possible by thermo-mechanical treatment.

The transformation of SiC etching shapes by high-temperature annealing has been investigated. Without silicon atoms on the surface, transformation of the etching shapes hardly occurred even after annealing in pure Ar at 1700 °C, where transformation should occur without the loss of silicon atoms. When SiH4 was added to Ar, the surface tended to revert to SiC, and the transformation was enhanced with increasing SiH4 addition. Therefore, the presence of silicon atoms is necessary to transform the etching shapes on SiC surfaces.

Recently, the improvement of the high strength of fine grain steels has been investigated actively. Fine grained steels have high yield stress, as expected by the Hall-Petch relationship. Therefore, these materials are considered for use as structural material. Welding is one of the most effective methods for connecting structural components. Nevertheless, the negative influence of tensile residual stresses and coarse grains due to the welding process must be taken into consideration. It has been proved that the shot peening process can effectively overcome these problems. In this study, samples prepared with various mean grain sizes were processed by shot peening. The triaxial residual stress distribution after shot peening was measured by X-ray diffraction. Moreover, the distribution of the hardening effect and nanocrystalline layer near the shot peened surface was observed. In this paper, the relationships between the effects of triaxial residual stress, structure, fatigue and hardness are discussed. As a result, thin nanocrystalline layer was formed on the surface layer of over 90 percent of surface area. Therefore, hardness of the surface, fatigue limit and fatigue life improved. The surface of plastic flow layer became the starting point of the crack initiation. Moreover, compressive residual stress by shot peening processing was confirmed and the depth of the nanocrystalline layer and the plastic flow layer correlated with depth of changing point of the triaxial residual stress distribution.

Microwave processing, as a new method for sintering ceramics, has key advantages such as increased heating rate, uniform heating and reduced cost compared to conventional methods. It is generally accepted that microwave sintering can improve the macroscopic mechanical performances of ceramics, however, the performances of microwave-sintered ceramics on the microscopic scale are rarely investigated. In the present study, the ceramics are sintered by hybrid microwave sintering (HMS), which combines the characteristics of microwave heating and conventional heating. To evaluate the homogeneous performance of the sintered ceramics, the behaviors of thermal residual stress distribution in the microwave-sintered and conventionally sintered ceramics were investigated by X-ray diffraction technique. The thermal residual stress investigation shows microwaves can sinter ceramics in entire volume while offering improved mechanical properties. Subsequently, the distribution behaviors of pore ratio and hardness in the ceramics were investigated, respectively. The experiment results confirm that the sinterability of ceramics is homogenously improved by hybrid microwave sintering.

Aging behavior and mechanical properties of ultra fine grained Cu-Cr-Zr alloy sheet produced by accumulative roll bonding (ARB) process were investigated. A Cu-0.85Cr-0.07Zr (in mass%) alloy was solution treated and then cold-rolled at ambient temperature in the sheet of 1 mm thick. The sheets were heavily deformed by ARB process at ambient temperature up to 5 cycles. The grain size was reduced down to 210 nm and the fraction of high angle grain boundaries (HAGB’s) in the specimen after ARB process was 63%. The proof stress ( σ 0.2) and elongation were 540 MPa and 10%, respectively. Due to the aging treatment, a little grain growth took place (240 nm) and the fraction of HAGB’s was increased to 67%. The proof stress and elongation of the aged one increased to 605 MPa and 15%, respectively. It was noteworthy that the electrical conductivity remarkably increased from 35% to 79%IACS by the aging treatment. It was concluded that the aging treatment after ARB process enhanced not only the mechanical properties but also the electrical conductivity in the Cu-Cr-Zr alloys.

Aging behavior and mechanical properties of ultra fine grained Cu-Cr-Zr alloy sheet produced by accumulative roll bonding (ARB) process were investigated. A Cu-0.85Cr-0.07Zr (in mass%) alloy was solution treated and then cold-rolled at ambient temperature in the sheet of I mm thick. The sheets were heavily deformed by ARB process at ambient temperature up to 5 cycles. The grain size was reduced down to 210 nm and the fraction of high angle grain boundaries (HAGB's) in the specimen after ARB process was 63%. The proof stress (sigma(0.2)) and elongation were 540 MPa and 10%, respectively. Due to the aging treatment, a little grain growth took place (240 nm) and the fraction of HAGB's was increased to 67%. The proof stress and clongation of the aged one increased to 605 MPa and 15 , respectively. It was noteworthy that the electrical conductivity remarkably increased from 35% to 79%IACS by the aging treatment. It was concluded that the aging treatment after ARB process enhanced not only the mechanical properties but also the electrical conductivity in the Cu-Cr-Zr alloys.

This article deals with the characterization of the mechanical behaviors of spheroidized carbon steels, which contain ferrite and spheroidal cementite. The aim of the study is to identify the deformation behaviors of cementite particles by x-ray diffraction and to correlate them to the residual stress state evolution. The stress state evolutions for both phases during an in situ 4-point bending test and after a uniaxial tensile test that have been well followed by x-ray diffraction. After each tensile loading, optical observation is made to correlate the determined residual stress state with the microstructure. The coupling of techniques helps us to characterize the deformation evolution of spheroidal cementite in the carbon steel: at the initial state, the cementite shows the same elastic behavior as the ferrite; at the next state, the ferrite begins to deform plastically but the cementite deforms elastically; then, plastic relaxation occurs in the ferrite while the cementite still deforms elastically until finally breaking.

Hydroxyapatite (HA) coatings have been widely used to provide a biocompatible surface on the dental and prosthetic implants. To improve the mechanical strength of the coating, we choose HA-glass functionally graded materials as coating materials. The functionally graded structure has been proved to be able to mitigate the residual stresses in materials near the interface of the coating and the substrate. The residual stresses are mainly caused by the mismatch in thermal expansions of the coating material and the substrate material. However, it is also a crucial requirement to evaluate the effect of the spatial distribution of constituent phases on the thermal residual stress distributions in the functionally graded coatings. With this aim, we measure the thermal residual states in the coatings by means of X-ray diffraction technique and simulate them using a computational model which applies the finite element method at the microscale. The experimental and the computational results show that the graded compound HA-glass interlayer structure can mitigate internal stresses and control the density and kinetics of misfit emanating from interfaces effectively.