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The tribological behavior of CrMoN films with respect to surface chemistry was investigated by using X-ray photoelectron spectroscopy (XPS). All of the films were prepared from a hybrid PVD system consisting of DC unbalanced magnetron (UBM) sputtering and arc ion plating (AIP) sources. The tribological property of the films was evaluated by a friction coefficient using a Ball-on-disk type tribometer. The chemistry of wear track was analyzed by energy dispersive spectroscopy (EDS) and XPS. The friction coefficient was measured to be 0.4 for the CrMoN film, which is lower than that of a monolithic CrN film. EDS and XPS results imply the formation of an oxide layer on the coating surface, which was identified as molybdenum oxide phases, known to be a solid lubricant during the wear test.

keyword : X-ray photoelectron spectroscopy, XPS, tribology, CrMoN, hybrid PVD

Self-organized ruthenium (Ru) dots were fabricated by 400℃ RTA (rapid thermal annealing) and ALD (atomic layer deposition). The dots were produced under the 400℃ RTA conditions for 10, 30 and 60 seconds on all Si (100)/200 nm-SiO2, glass, and glass/fluorine-doped tin oxide (FTO) substrates, Electrical sheet resistance, and surface microstructure were examined using a 4-point probe and FE-SEM (field emission scanning electron microscopy). Ru dots were observed when a 30 nm-Ru layer on a Si (100)/200 nm-SiO2 substrate was annealed for 10, 30 and 60 seconds, whereas the dots were only observed on a glass substrate when a 50 nm-Ru layer was annealed on glass. For a glass/FTO substrate, RTA <30 seconds was needed for 30 nm Ru thick films. Those dots can increase the effective surface area for silicon and glass substrates by up to 5-44%, and by 300% for the FTO substrate with a < 20° wetting angle.

keyword : Ru dots, annealing, agglomeration, ALD, RTA

The wetting property and reflectivity of Sn-3.5Ag solder which was dip coated on a LED lead frame were investigated. The wettability of molten solder on Cu substrate was evaluated by the wetting balance tester, and surface tension was calculated from maximum withdrawal force and withdrawal time. Temperature of the molten solder in a bath was varied in the range of 250-290℃. With increasing temperature, the surface tension decreased a little. The reflectivity of Sn-3.5Ag coated on a substrate became a little lower than the highest current LED lead frame reflectivity.

keyword : Alloys, soldering, wetting, surface roughness, reflectivity

In order to understand the difference in SiC deposition between the CH3SiCl3-H2 and C3H8-SiCl4-H2 systems, we calculate the phase stability among B-SiC, graphite and silicon. We constructed the phase-diagram of B-SiC over graphite and silicon via computational thermodynamic calculation considering pressure (P), temperature (T) and gas composition (C) as variables. Both P-T-C diagrams showed a very steep phase boundary between the SiC+C and SiC region perpendicular to the H/Si axis, and also showed an SiC+Si region with a H/Si value of up to 6700 in the C3H8-SiCl4-H2, and 5000 in the CH3SiCl3-H2 system, This difference in phase boundaries is explained by the ratio of Cl to Si, which is 4 for the C3H8-SiCl4-H2 system and 3 for the C3H8-SiCl4-H2 system. Because the C/Si ratio is fixed at 1 in the CH3SiCl3-H2 system while it can be variable in the C3H8-SiCl4-H2 system, the functionally graded material is applicable for better mechanical bonding during SiC coating on graphite substrate in the C3H8-SiCl4-H2 system.

keyword : Thin film, vapor deposition, phase diagram, thermodynamic Calculation, computer simulation

Medium carbon steel was aluminized by hot dipping into molten Al or Al-1 at% Si baths. After hot-dipping in these baths, a thin Al-rich topcoat and a thick alloy layer rich in Al5Fe2 formed on the surface. A small amount of FeAl and Al3Fe was incorporated in the alloy layer. Silicon from the Al-1 at% Si bath was uniformly distributed throughout the entire coating. The hot dipping increased the microhardness of the steel by about 8 times. Heating at 700-1000, however, decreased the microhardness through interdiffusion between the coating and the substrate. The oxidation at 700-1000 in air formed a thin protective a-Al2O3 layer, which provided good oxidation resistance. Silicon was oxidized to amorphous silica, exhibiting a glassy oxide surface.

keyword : Metals, surface modification, microstructure, scanning electron microscopy (SEM), hot-dip aluminizing

This work is concerned with a statistical approach to the life prediction on irradiation-assisted stress corrosion cracking (IASCC) of stainless steel (SS) for core internals of a pressurized water reactor (PWR). The previous results of the time-to-failure of IASCC measured on neutron-irradiated stainless steel components were statistically analyzed in terms of stress and irradiation. The accelerating life testing model of IASCC of cold worked Type 316 SS was established based on an inverse power model with two stressvariables, the applied stress and irradiation dose. Considering the variation of the yield strength and applied stress with the irradiation dose in the model, the remaining life of the baffle former bolt was statistically predicted during operation under complex environments of stress and irradiation.

keyword : Alloys, aging, corrosion, tensile test, accelerated life testing model, irradiation-assisted stress corrosion cracking

This paper presents regularly micro-textured glass surfaces ensuring the superhydrophobic properties in the Cassie-Baxter regime. The proposed surfaces were fabricated simply and efficiently by filling the glass material into a silicon micro-mold with periodic micro-cavities based on a thermal-reflow process, resulting in a successful demonstration of the textured glass surface with periodically-arrayed micro-pillar structures. The static and dynamic wetting properties of the micro-textured glass surfaces were characterized by measuring the static contact angle (SCA) and contact angle hysteresis (CAH), respectively. In addition, the surface wettability was estimated theoretically based on Wenzel and Cassie-Baxter wetting theories, and compared with the experimental ones. Through the experimental and theoretical observations, it was clearly confirmed that the proposed micro-textured glass surfaces showed the slippery superhydrophobic behaviors in the Cassie-Baxter wetting mode.

keyword : Glasses, surface modification, texture, wetting, superhydrophobicity

The microstructure of a hammer scale excavated from the Bogam-ri was examined in an effort to understand the iron technologies applied in the manufacturing of an iron forging process technology. The microstructures of oxide layer in the hammer scale were found to have crucial information about the ancient iron forging process treatment. The microstructure observed in the hammer scale can be distinguished by the forging process. First, the microstructure of the oxide layer in the hammer scale created by the forging process is Wstite (FeO) in the form of leaves. Latterly, the microstructure of the Wustite (FeO) in the hammer scale is observed to be in the form of a flat shape formed by a repeating forging process.

keyword : Hammer scale, bloomery iron, bogam-ri, forging process, slag

ZnO nanostructures were grown on R-plane sapphire substrates with seed layers annealed at different temperatures ranging from 600 to 800℃. The properties of the ZnO nanostructures were investigated by scanning electron microscopy, high-resolution X-ray diffraction, UV-visible spectrophotometer, and photoluminescence. For the as-prepared seed layers, ZnO nanorods and ZnO nanosheets were observed. However, only ZnO nanorods were grown when the annealing temperature was above 700℃. The crystal qualities of the ZnO nanostructures were enhanced when the seed layers were annealed at 700℃. In addition, the full width at half maximum (FWHM) of near-band-edge emission (NBE) peak was decreased from 139 to 129meV by increasing the annealing temperature to 700℃. However, the FWHM was slightly increased again by a further increase in the annealing temperature. Optical transmittance in the UV region was almost zero, while that in the visible region was gradually increased as the annealing temperature increased to 700℃. The optical band gap of the ZnO nanostructures was increased as the annealing temperature increased to 700℃. It is found that the optical properties as well as the structural properties of the rod-shaped ZnO nanostructures grown on R-plane sapphire substrates by hydrothermal method are improved when the seed layers are annealed at 700℃.

keyword : ZinC oxide, nanostructured, materials, chemical synthesis, optical properties, scanning electron microscopy

We report on electrical and mechanical properties of silicon nitride (SiNx) films deposited by a plasma enhanced chemical vapor deposition (PECVD) method at 200℃ from SiH4 highly diluted in N2. The films were also prepared from SiH4 diluted in He for comparison. The N2 dilution was also effective in improving adhesion of the SiNx films, fascilitating construction of thin film transistors (TFTs). Metalinsulator-semiconductor (MIS) and Metal-insulator-Metal (MIM) structures were used for capacitance-voltage (C-V) and current-voltage (I-V) measurements, respectively. The resistivity and breakdown field strength of the SiNx films from N2-diluted SiH4 were estimated to be 1×1013Ω · cm, 7.4 MV/cm, respectively. The MIS device showed a hysteresis window and a flat band voltage shift of 3 V and 0.5 V, respectively. The TFTs fabricated by using these films showed a field-effect mobility of 0.16 cm2/Vs, a threshold voltage of 3 V, a subthreshold slope of 1.2V/dec, and an on/off ratio of >106.

keyword : Diclectrics, vapor deposition, electrical properties, conductivity/resistivity, PECVD, silicon nitride, lowtemperature, TFT, highly-diluted gas