Jung-Yeul Kim

Effect of CaO addition on the firing voltage of MgO films in AC plasma display panels

In order to improve both operating voltage and memory coefficient of a protective layer for AC plasma display panels, controlled amount of alkaline earth oxide (CaO) was added to the pure MgO to replace the conventional pure MgO protective layer. The effects of CaO addition on both the electrical properties (Vf and Vs) and the microstructure of the Mg1−xCaxO thin films deposited on slide glass substrates by e-beam evaporation were investigated. Distinct changes in both peak intensity and diffraction peak positions of Mg–Ca–O films were observed with increasing [CaO/(MgO+CaO)] ratio owing to the strong atomic interaction between Mg and Ca. When the [CaO/(MgO+CaO)] ratio was increased to 0.1, the intensities of both (111) and (200) peaks were observed to increase with corresponding peak shift to lower diffraction peak positions as a result of the strong interdiffusion from the Ca and Mg atomic interactions. When the [CaO/(MgO+CaO)] ratio of 0.1 was used, the deposited films exhibited an enhanced operating performance with an improved memory coefficient. By adding a controlled amount of CaO, the deposited Mg–Ca–O films showed a firing voltage of 176 V that is lower than that of the conventional 100% MgO film.

Stoichiometry dependence of electrochemical performance of thin-film SnOx microbattery anodes deposited by radio frequency magnetron sputtering

Thin-film SnOx microbattery anodes, with various oxygen deficiencies, are deposited from a SnO2 target on to an ambient temperature substrate by radio frequency (RF) magnetron sputtering. The high reversible capacity and cycle performance characteristics of SnOx are described. RF power density and process gas pressure during deposition are fixed at 2.5 W/cm2 and 10 mTorr, respectively. The SnOx films are characterized by energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Constant-current galvanostatic charge–discharge tests of half cells are also performed. The stoichiometric parameter x increases with the increase in oxygen partial pressure, but decreases when the number of Sn chips placed on the target material in an argon atmosphere are increased. It is observed that SnOx transforms to lithium oxide and metallic Sn after an initial Li intercalation reaction. The charge–discharge performance of the tin oxide films is found to be dependent on stoichiometry. In the present work, SnO1.43 is the optimum stoichiometry, exhibiting the highest reversible capacity (498.33 μA h/cm2 μm) and the lowest irreversible capacity (301.79 μA h/cm2 μm).

Effects of silver additions on the mechanical properties and resistance to thermal shock of YBa2Cu3O7–δ superconductors

Abstract We evaluated the effects of silver (Ag) additions on the mechanical properties and resistance to thermal shock of bulk YBa2Cu3O7–δ (YBCO) superconductors. Various amount of Ag was added to YBCO by two different mixing techniques, i.e. in the form of metallic Ag powder and AgNO3 powder. It was observed that the bending strength (strength), fracture toughness and resistance to thermal shock of YBCO increased with increasing Ag content, probably due to strengthening mechanisms by the addition of Ag. In addition, YBCO-Ag composites made by mixing with AgNO3 showed slightly higher strength, fracture toughness and resistance to thermal shock as compared with those made by mixing with metallic Ag powder. The improvement in the resistance to thermal shock is believed to be due to improvements in the strength, fracture toughness and thermal conductivity of YBCO-Ag composites resulting from Ag additions.

Deposition mechanism of MOCVD copper films in the presence of water vapor

Abstract The effect of water vapor on the initial nucleation and growth mechanisms of metallo-organic chemical vapor deposited (MOCVD) copper films from copper(II) hexafluoroacetylacetonate (Cu(hfac)2) on a pre-deposited Cr substrate has been investigated. A relatively low growth rate with a long incubation period was observed in the absence of water vapor. When an optimum water vapor flow rate was introduced into the system, enhanced growth rate was observed without degrading electrical properties of the copper film. However, XRD analysis of the initial deposited film revealed that the film mainly consisted of copper oxide (Cu2O). The oxygen in the copper oxide films deposited from Cu(hfac)2 on pre-deposited Cr substrates is originated from the water vapor and not from the hfac ligand. Initial nucleation and growth of the deposited film is initiated by the reaction between the vapor phase precursor and water vapor forming copper oxide (Cu2O) at the surface and the oxide is then reduced to metallic copper by either a disproportionation reaction or by hydrogen molecules. The optimum water vapor flow rate is thus believed to be the driving force for the enhanced growth rate and a reduced nucleation delay without degrading the film resistivity.

Low-voltage characteristics of MgO-CaO films as a protective layer for AC plasma display panels by e-beam evaporation

The MgO-CaO composites films were prepared by e-beam evaporation to improve both operating voltages and memory coefficient of a protective layers for AC plasma display panels (PDPs). The effects of CaO addition to the conventional MgO films on both the electrical properties and the structural changes of the Mg1−xCaxO thin films deposited on the slide glass substrates were investigated. Atomic force microscopy (AFM) results revealed that the Mg0.8Ca0.2O film had a very rough surface due to the formation of a second phase on the surface. By adding controlled amount of CaO, the Mg-Ca-O films showed a firing voltage of 176 V that is lower than that of the conventional 100% MgO film. The deposition rates of 40–100 nm/min were obtained as a function of [CaO/(MgO + CaO)] ratio of the evaporation source materials.

Surface characteristics of a porous-surfaced Ti-6Al-4V implant fabricated by electro-discharge-compaction

Electro-discharge-compaction (EDC) is a unique method for producing porous-surfaced metallic implants. The objective of the present studies was to examine the surface characteristics of the Ti-6Al-4V implants formed by EDC. Porous-surfaced Ti-6Al-4V implants were produced by employing EDC using 480 μF capacitance and 1.5 kJ input energy. X-ray photoelectron spectroscopy was used to study the surface characteristics of the implant materials. C, O, and Ti were the main constituents, with smaller amounts of Al and V. EDC Ti-6Al-4V also contained N. Titanium was present mainly in the forms of mixed oxides and small amounts of nitride and carbide were observed. Al was present in the form of aluminum oxide, while V in the implant surface did not contribute to the formation of the surface oxide film. The surface of conventionally prepared Ti-6Al-4V primarily consists of TiO2, whereas, the surface of the EDC-fabricated Ti-6Al-4V consists of complex Ti and Al oxides as well as small amounts of titanium carbide and nitride components. However, preliminary studies indicated that the implant was biocompatible and supports rapid osseointegration.

Effects of hydrogen plasma pretreatment on characteristics of copper film deposited by remote plasma CVD using (hfac)Cu(TMVS)

Abstract The effects of remote hydrogen plasma pretreatment on the characteristics of copper films prepared by remote plasma chemical vapor deposition (RPCVD) using copper(I) hexafluoroacetylacetonate trimethylvinylsilane [Cu(hfac)(TMVS)] were studied at a pressure of 1 torr, substrate temperature of 200°C, and plasma power of 100 W. When the remote hydrogen plasma pretreatment was employed, catalytic active points were observed on the surface of the pre-deposited 500-A thick TiN substrate. These active points reduced the incubation time required for the copper nucleation on the pre-deposited TiN substrate. Enhanced copper nucleation rates were observed on the hydrogen plasma pretreated TiN substrate owing to the high concentration of the reactive hydrogen species in the reaction zone, thereby enhancing the reduction reaction and leading to improved copper qualities and increased nucleation rates. The resistivity measurements of the films yielded film resistivities in the range of approximately 2.1±0.1 μΩ cm for most samples.

Thermal stability enhancement of Cu/WN/SiOF/Si multilayers by post-plasma treatment of fluorine-doped silicon dioxide

The effect of a post-plasma treatment on the dielectric property and reliability of fluorine doped silicon oxide (SiOF) film was studied. Also, the thermal stability of the Cu/WN interconnect system with SiOF interlayer dielectrics was examined by rapid thermal annealing. The surface roughness of SiOF films increased with increasing plasma treatment power due to ion bombardment effect during the plasma treatment. As the plasma treatment power increased, the dielectric constant increased from 3.16 to 3.43, while the change in the relative dielectric constant of the plasma treated films decreased in magnitude after treatment at 100 °C for 30 min in boiling water. Furthermore, the chemical properties of the plasma treated SiOF layers near the top surface tend to resemble those of thermal oxides after plasma treatment with sufficient plasma power, apparently due to the reduction in the Si–F bonding in the films. In the case of a Cu/WN/SiOF/Si multilayer structure, surface oxidation and densification due to th...

Convenient Aluminizing Process of Steel by Using Al-Ti Mixed Powder Slurry

)Abstract In this study, we attempted to develop a convenient aluminizing process, using Al-Ti mixed slurryas an aluminum source, to control the Al content of the aluminized layer as a result of a one-step process andcan be widely adopted for coating complex-shaped components. The aluminizing process was carried out by theheat treatment on disc and rod shaped S45C steel substrates with Al-Ti mixed slurries that were composedof various mixed ratios (wt%) of Al and Ti powders. The surface of the resultant aluminized layer was relativelysmooth with no obvious cracks. The aluminized layers mainly contain an Fe-Al compound as the bulk phase.However, the Al concentration and the thickness of the aluminized layer gradually decrease as the Tiproportion among Al-Ti mixed slurries increases. It has also been shown that the Al-Ti compound layer, whichformed on the substrate during heat treatment, easily separates from the substrate. In addition, theincorporation of Ti into the substrate surface during heat treatment was not observed.Key wordsaluminizing process, Al-Ti mixed powder slurry, aluminized layer, Fe-Al compound, Al-Ticompound.

Conditioning effects on La1-xSrxMnO3-Yttria stabilized Zirconia electrodes for thin-film solid oxide fuel cells

Composite cathodes of 50/50 vol percent LSM-YSZ (La1-xSrxMnO3-yttria stabilized zirconia) were deposited onto dense YSZ electrolytes by a colloidal deposition technique. The cathode characteristics were then examined by scanning electron microscopy (SEM) and studied by an impedance spectroscopy (IS). Conditioning effects of the LSM-YSZ cathodes were seen, and remedies for these effects were proposed for improving the performance of a solid oxide fuel cell (SOFC). LSM surface contamination and modification, cathode bonding to the YSZ electrolyte, changing Pt electrode and bonding paste, and curvature of sintered YSZ electrolytes led to some changes in microstructure and variability in cell performances.