• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.181.2-181.2
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• 2014

A single-layer graphene has been uniformly grown on a Cu surface at elevated temperatures by thermally processing a poly (methyl methacrylate) (PMMA) film in a rapid thermal annealing (RTA) system under vacuum. The detailed chemistry of the transition from solid-state carbon to graphene on the catalytic Cu surface was investigated by performing in-situ residual gas analysis while PMMA/Cu-foil samples being heated, in conjunction with interrupted growth studies to reconstruct ex-situ the heating process. We found that the gas species of mass/charge (m/e) ratio of 15 ($CH_3{^+}$) was mainly originated from the thermal decomposition of PMMA, indicating that the formation of graphene occurs with hydrocarbon molecules vaporized from PMMA, such as methane and/or methyl radicals, as precursors rather than by the direct graphitization of solid-state carbon. We also found that the temperature for dominantly vaporizing hydrocarbon molecules from PMMA and the length of time, the gaseous hydrocarbon atmosphere is maintained, are dependent on both the heating temperature profile and the amount of a solid carbon feedstock. From those results, we strongly suggest that the heating rate and the amount of solid carbon are the dominant factors to determine the crystalline quality of the resulting graphene film. Under optimal growth conditions, the PMMA-derived graphene was found to have a carrier (hole) mobility as high as ${\sim}2,700cm^2V^{-1}s^{-1}$ at room temperature, which is superior to common graphene converted from solid carbon.

• Journal of The Korean Society of Grassland and Forage Science
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• v.34 no.2
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• pp.114-119
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• 2014

Salinity and drought stresses are probably the most significant abiotic factor limiting plant's growth, also negatively affect seed germination and early seedling development. To study on effect of NaCl and PEG stress on seed germination and gene expression pattern of tall fescue, the levels of NaCl and PEG-induced water stresses were determined in first experiment. Different concentration of NaCl (0 to 350 mM) and PEG (0 to 30%) were used for seed treatment. Seed Germination percentage reduced with increasing osmotic potential of growth medium either due to NaCl or PEG. Seeds were not germinate at 350 mM NaCl or 30% PEG treatment. On the basis of the results, Kentucky31(E-) had more resistant than Fawn in both stress conditions. Furthermore, we have used an annealing control primer-based differential display reverse transcription-polymerase chain reaction method to identify salt- and drought stress-induced differentially expressed genes (DEGs) in tall fescue leaves. Using 120 annealing control primers, a total of 4 genes were identified and sequenced. The possible roles of the identified DEGs are discussed in the context of their putative role during salinity and drought stresses.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.73-81
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• 2006

Heat treatment condition for the stabilization of foamed glass block through the foaming process of the hydrolized waste glass was investigated and scale-up test for the manufacturing of foamed glass was also attempted for the actual foaming process. Proper heat treatment condition was quenching from the foaming temperature to $550{\sim}600^{\circ}C$ for stabilization, and then annealing from stabilization temperature to $200^{\circ}C$ and holding up at $200^{\circ}C$ for removal thermal stress, and then annealing to the room temperature with cooling speed of $0.3^{\circ}C/min$. Through this heat treatment conditions, foamed glass block with size of $250mm{\times}250mm{\times}90mm$ was produced successfully. The properties of this foamed glass block showed density of $0.28{\pm}0.06g/cm^3$, thermal conductivity of $0.048{\pm}0.005kcal/hm^{\circ}C$, moisture absorption of $0.5{\pm}0.09vol%$, linear expansion coefficient of $(8.6{\pm}0.2){\times}10^{-6}m/m^{\circ}C$($400^{\circ}C$), flexural strength of $15.0{\pm}0.6kg/cm^2$, and compression strength of $39.5{\pm}0.6kg/cm^2$.

• Journal of the Korean Electrochemical Society
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• v.2 no.1
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• pp.5-12
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• 1999

By the PVA-precursor method, polycrystalline powder of $Li_xNi_{1-y}Co_yO_2$, cathode material for lithium battery, was synthesized. Using the powder as the cathode material, lithium ion batteries were fabricated, whose electrochemical properties were measured. The effect of changing synthetic conditions, such as PvA/metal mole ratio, concentration of PVA, degree of polymerization of PVA, pyrolysis condition, and metal stoichiometry, on the battery performance was investigated. Considering the initial performance of the cell, the optimum stoichiometry of the $Li_xNi_{1-y}Co_yO_2$, synthesized by the PVA-precursor method was observed to be x: 1.0 and y=0.26. A minor phase of $Li_2CO_3$, which was generated by the residual carbon in the powder precursor, deteriorated the performance of the cell. In order to eliminate the minor phase, the precursor had to be pyrolyzed under the flow of dry air. Annealing the powder at $500^{\circ}C$ under the flow of dry air also eliminated the minor phase, and the performance of the cell was largely improved by the treatment.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.229-229
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• 2010

With the scaling down of ultra large integrated circuits (ULSI) to the sub-50 nm technology node, the need for an ultra-thin, continuous and conformal diffusion barrier and Cu seed layer is increasing. However, diffusion barrier and Cu seed layer formation with a physical vapor deposition (PVD) method has become difficult as the technology node is reduced to 30 nm and beyond. Recent work on self-forming barrier processes using PVD Cu alloys have attracted great attention due to the capability of conformal ultra-thin barrier formation using a simple technique. However, as in the case of the conventional barrier and Cu seed layer, PVD of the Cu alloy seed layer will eventually encounter the difficulty in conformal deposition in narrow line trenches and via holes. Atomic layer deposition (ALD) has been known for its good step coverage and precise thickness control, and is a candidate technique for the formation of a thin conformal barrier layer and Cu seed layer. Conformal Cu-Mn seed layers were deposited by plasma enhanced atomic layer deposition (PEALD) at low temperature ($120^{\circ}C$), and the Mn content in the Cu-Mn alloys were controlled form 0 to approximately 10 atomic percent with various Mn precursor feeding times. Resistivity of the Cu-Mn alloy films decreased by annealing due to out-diffusion of Mn atoms. Out-diffused Mn atoms were segregated to the surface of the film and interface between a Cu-Mn alloy and $SiO_2$, resulting in self-formed $MnO_x$ and $MnSi_xO_y$, respectively. No inter-diffusion was observed between Cu and $SiO_2$ after annealing at $500^{\circ}C$ for 12 h, indicating an excellent diffusion barrier property of the $MnSi_xO_y$. The adhesion between Cu and $SiO_2$ was enhanced by the formation of $MnSi_xO_y$. Continuous and conductive Cu-Mn seed layers were deposited with PEALD into 32 nm $SiO_2$ trench, enabling a low temperature process, and the trench was perfectly filled using electrochemical plating (ECD) under conventional conditions. Thus, it is the resultant self-forming barrier process with PEALD Cu-Mn alloy film as a seed layer for plating Cu that has further potential to meet the requirement of the smaller than 30 nm node.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.6
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• pp.235-242
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• 2018

High temperature electrical conductivity of Aluminum Nitride (AlN) ceramics sintered with $Y_2O_3$ as a sintering aid has been investigated with respect to various sintering conditions and MgO-dopant. When magnesium oxide is added as a dopant, liquid glass-film and crystalline phases such as spinel, perovskite are formed as second phases, which affects their electrical properties. According to high temperature impedance analysis, MgO doping leads to reduction of activation energy and electrical resistivity due to AlN grains. On the other hand, the activation energy and electrical resistivity due to grain boundary were increased by MgO doping. This is a result of the formation of liquid glass film in the grain boundary, which contains Mg ions, or the elevation of schottky barrier due to the precipitation of Mg in the grain boundary. For the annealed sample of MgO doped AlN, the electrical resistivity and activation energy were increased further compared to MgO doped AlN, which results from diffusion of Mg in the grains from grain boundary as shown in the microstructure.

• Membrane Journal
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• v.32 no.6
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• pp.456-464
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• 2022

Hydrogen permeation performance was analyzed by manufacturing Pd and Pd-Cu membranes through electroless plating. As a support for the Pd and Pd-Cu membranes, α-Al₂O₃ ceramic hollow fiber were used. Pd-Cu membrane was manufactured through sequential electroless plating, and then annealing was performed at 500°C, for 18 h in a hydrogen atmosphere to make Pd and Cu alloy. After annealing, the Pd-Cu membrane confirmed that the alloy was formed through EDS (Energy Dispersive X-ray Spectroscopy) and XRD (X-ray Diffraction) analysis. In addition, the thickness of the Pd and Pd-Cu plating layers were measured to be about 3.21 and 3.72 µm, respectively, through SEM (Scanning Electron Microscope) analysis. Hydrogen permeation performance was tested for hydrogen permeation in the range of 350~450°C and 1~4 bar in hydrogen single gas and mixed gas (H₂, N₂). In a single hydrogen gas, Pd and Pd-Cu membranes have flux of up to 54.42 and 67.17 ml/cm²⋅ min at 450 °C and 4 bar. In the mixed gas, it was confirmed that the separation factors of 1308 and 453 were obtained under the conditions of 450 °C and 4 bar.

• Journal of Institute of Convergence Technology
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• v.8 no.1
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• pp.33-39
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• 2018

The screen printing method for forming the electrode by applying the existing pressure is difficult to apply to thin wafers, and since expensive Ag paste is used, it is difficult to solve the problem of cost reduction. This can solve both of the problems by forming the front electrode using a plating method applicable to a thin wafer. In this paper, the process conditions of electrode formation are optimized by using LIEP (Light-Induced Electrode Plating). Experiments were conducted by varying the Ni plating bath temperature $40{\sim}70^{\circ}C$, the applied current 5 ~ 15 mA, and the plating process time 5 ~ 20 min. As a result of the experiment, it was confirmed that the optimal condition of the structural characteristics was obtained at the plating bath temperature of $60^{\circ}C$, 15 mA, and the process time of 20 min. The Cu LIEP process conditions, experiments were conducted with Cu plating bath temperature $40{\sim}70^{\circ}C$, applied voltage 5 ~ 15 V, plating process time 2 ~ 15 min. As a result of the experiment, it was confirmed that the optimum conditions were obtained as a result of electrical and structural characteristics at the plating bath temperature of $60^{\circ}C$ and applied current of 15 V and process time of 15 min. In order to form Ni silicide, the firing process time was fixed to 2 min and the temperature was changed to $310^{\circ}C$, $330^{\circ}C$, $350^{\circ}C$, and post contact annealing was performed. As a result, the lowest contact resistance value of $2.76{\Omega}$ was obtained at the firing temperature of $310^{\circ}C$. The contact resistivity of $1.07m{\Omega}cm^2$ can be calculated from the conditionally optimized sample. With the plating method using Ni / Cu, the efficiency of the solar cell can be expected to increase due to the increase of the electric conductivity and the decrease of the resistance component in the production of the solar cell, and the application to the thin wafer can be expected.

• Journal of Magnetics
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• v.11 no.1
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• pp.16-19
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• 2006

$2-\mu{m}$ thick GaN epilayer was prepared, and 80 KeV $Co^{-}$ ions with a dose of $3X10^{16}\;cm^{-2}$ were implanted into GaN at $350^{\circ}C$. The implanted samples were post annealed at $700^{\circ}C$. We have investigated the magnetic and structural properties of Co ion-implanted GaN by various measurements. HRXRD results did not show any peaks associated with second phase formation and only the diffraction from the GaN layer and substrate structure were observed. SIMS profiles of Co implanted into GaN before and after annealing at $700^{\circ}C$ have shown a projected range of $\sim390\AA$ with 7.4% concentration and that there is little movement in Co. AFM measurement shows the form of surface craters for $700^{\circ}C$-annealed samples. The magnetization curve and temperature dependence of magnetization taken in zero-field-cooling (ZFC) and field-cooling (FC) conditions showed the features of superparamagnetic system in film. XPS measurement showed the metallic Co 2p core levels spectra for $700^{\circ}C$-annealed samples. From this, it could be explained that magnetic property of our films originated from Co magnetic clusters.

• Corrosion Science and Technology
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• v.14 no.2
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• pp.93-98
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• 2015

Recently, Stainless steels have been increasingly selected as the fitting or the valve materials of water pipes as the human health issue is getting higher and higher. Therefore, the connectors attached at pipes to deliver water are exposed to more severe environments than the pipes because crevice or galvanic corrosion is apt to occur at the fittings or the valves. Effects of the solid solution annealing, cooling rate after this heat treatment, and passivation on the corrosion properties of the shell mold casted SSC13 (STS304 alloy equivalent) were studied. The heating and quenching treatment more or less reduced hardness but effectively improved corrosion resistance. It was explained by the reduction of delta ferrite contents. Independent of heat treatment, the chemical passivation treatment also lowered corrosion rate but the improvement of corrosion resistance depended on temperature and time for passivation treatment indicating that the optimum conditions for passivation treatment were the bath temperature of $34^{\circ}C$ and operating time of 10 minutes. Therefore it is suggested that the corrosion resistance of SSC13 can be effectively improved with the heat treatment, where SSC13 is heated for 10 minutes at $1120^{\circ}C$ and quenched and passivation treatment, where SSC13 is passivated for at least 10 seconds at $34^{\circ}C$ nitric acid solution.