• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.380-381
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• 2012

Bioinspired sea urchin-like structures were fabricated on silicon by inductively coupled plasma (ICP) etching using lens-like shape hexagonally patterned photoresist (PR) patterns and subsequent metal-assisted chemical etching (MaCE) [1]. The lens-like shape PR patterns with a diameter of 2 ${\mu}m$ were formed by conventional lithography method followed by thermal reflow process of PR patterns on a hotplate at $170^{\circ}C$ for 40 s. ICP etching process was carried out in an SF6 plasma ambient using an optimum etching conditions such as radio-frequency power of 50 W, ICP power of 25 W, SF6 flow rate of 30 sccm, process pressure of 10 mTorr, and etching time of 150 s in order to produce micron structure with tapered etch profile. 15 nm thick Ag film was evaporated on the samples using e-beam evaporator with a deposition rate of 0.05 nm/s. To form Ag nanoparticles (NPs), the samples were thermally treated (thermally dewetted) in a rapid thermal annealing system at $500^{\circ}C$ for 1 min in a nitrogen environment. The Ag thickness and thermal dewetting conditions were carefully chosen to obtain isolated Ag NPs. To fabricate needle-like nanostructures on both the micron structure (i.e., sea urchin-like structures) and flat surface of silicon, MaCE process, which is based on the strong catalytic activity of metal, was performed in a chemical etchant (HNO3: HF: H2O = 4: 1: 20) using Ag NPs at room temperature for 1 min. Finally, the residual Ag NPs were removed by immersion in a HNO3 solution. The fabricated structures after each process steps are shown in figure 1. It is well-known that the hierarchical micro- and nanostructures have efficient light harvesting properties [2-3]. Therefore, this fabrication technique for production of sea urchin-like structures is applicable to improve the performance of light harvesting devices.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.5
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• pp.94-99
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• 2004

This study was carried out to find out what is the optimum conditions for RAPD of Zelkova serata. We changes the factors what affect to PCR band patterns, as a result, we established the optimum conditions as follows; template DNA 100mg, Primer 0.25uM, dNTP 100mM, Taq polymerase 1.0u, and total reaction volume was filled up to 10uL with distilled water. As the amount of primers went higher, PCR reaction rates were lowered. This reason was cause by exhaustion of primers during initial reaction. The amount of dNTP didn't showed noticable differtations between the range, but the optimum amount was 100mM for efficiency. Taq polymerase 1.0 unit was the best in the range. As the concentration of polymerase were increased, many non-specific bands were appeared, In primer selection, most Openron Random Primers are amplified in this experiment. The primers GC contents were 60, and set A, B, C, D, E, X were tested. Thermal cycler(ASTEC PC808, Japan) condition was, $95^{\circ}C$, 5min, initial denaturation, $94^{\circ}C$, 20sec, denaturation, $37^{\circ}C$, 40sec, annealing, $72^{\circ}C$, 1min, extention, 45cycle repeated and final extention $72^{\circ}C$10min.

• Polymer(Korea)
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• v.34 no.5
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• pp.391-397
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• 2010

Poly(amic acid)(PAA) was prepared by reaction of bicyclo(2,2,2)oct-7-ene-2,3,5,6-tetracarboxylicdianhydride(BTDA) containing double bond for crosslinking and bis[4-(3-aminophenoxy) phenyl] sulfone(BAPS) in N,N-dimethylacetamide(DMAc). The cast film of PAA was heat-treated at different temperatures to create polyimide(PI) films. With increasing thermal crosslinking temperatures from 250 to $350^{\circ}C$, the thermo-mechanical properties, degree of crosslinking, and optical transparency of the cross-linked PI were investigated. The maximum enhancement in the thermo-mechanical properties was observed at a heat treatment condition of $350^{\circ}C$. However, the optical transparency was found to be optimal for $250^{\circ}C$ heat treatment. The degree of crosslinking in NMR was determined to be 85% to 93% with increasing annealing temperature conditions from 250 to $350^{\circ}C$.

• Progress in Superconductivity and Cryogenics
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• v.17 no.2
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• pp.36-40
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• 2015

Electron cyclotron resonance (ECR) ion source is an essential component of heavy-ion accelerator. For a given design, the intensities of the highly charged ion beams extracted from the source can be increased by enlarging the physical volume of ECR zone [1]. Several models for ECR ion source were and will be constructed depending on their operating conditions [2-4]. In this paper three simulation models with 3, 4 and 6 solenoid system were built, but it's not considered anything else except the number of coils. Two groups of optimization analysis are presented, and the evolution strategy (ES) is adopted as an optimization tool which is a technique based on the ideas of mutation, adaptation and annealing [5]. In this research, the volume of ECR zone was calculated approximately, and optimized designs for ECR solenoid magnet system were presented. Firstly it is better to make the volume of ECR zone large to increase the intensity of ion beam under the specific confinement field conditions. At the same time the total volume of superconducting solenoids must be decreased to save material. By considering the volume of ECR zone and the total length of solenoids in each model with different number of coils, the 6 solenoid system represented the highest coil performance. By the way, a certain case, ECR zone volume itself can be essential than the cost. So the maximum ECR zone volume for each solenoid magnet system was calculated respectively with the same size of the plasma chamber and the total magnet space. By comparing the volume of ECR zone, the 6 solenoid system can be also made with the maximum ECR zone volume.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.146-149
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• 2002

The aim of stereotactic radiosurgery(SRS) is to deliver a high dose to a target region and a low dose to critical organ through only one or a few irradiation. To satisfy this aim, optimized irradiating conditions must be searched in the planning. Thus, many mathematical methods such as gradient method, simulated annealing and genetic algorithm had been proposed to find out the conditions automatically. There were some limitations using these methods: the long calculation time, and the difficulty of unique solution due to the different shape of tumor. In this study, optimization protocol using ideal models and data base was proposed. Proposed optimization protocol constitutes two steps. First step was a preliminary work. Some possible ideal geometry shapes, such as sphere, cylinder, cone shape or the combination, were assumed to approximate the real tumor shapes. Optimum variables such as isocenter position or collimator size, were determined so that the high dose region could be shaped to fit ideal models with the arrangement of multiple isocenter. Data base were formed with those results. Second, any shaped real targets were approximated to these models using geometry comparison. Then, optimum variables for ideal geometry were chosen from the data base predetermined, and final parameters were obtained by adjusting these data. Although the results of applying the data base to patients were not superior to the result of optimization in each case, it can be acceptable as a starting point of plan.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.17
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• pp.7409-7414
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• 2015

Loop-mediated isothermal amplification (LAMP) developed by Notomi et al. (2000) has made it possible to amplify DNA with high specificity, efficiency and rapidity under isothermal conditions. The ultimate products of LAMP are stem-loop structures with several inverted repeats of the target sequence and cauliflower-like patterns with multiple loops shaped by annealing between every other inverted repeats of the amplified target in the similar strand. Because the amplification process in LAMP is achieved by using four to six distinct primers, it is expected to amplify the target region with high selectivity. However, evaluation of reaction accuracy or quantitative inspection make it necessary to append other procedures to scrutinize the amplified products. Hitherto, various techniques such as turbidity assessment in the reaction vessel, post-reaction agarose gel electrophoresis, use of intercalating fluorescent dyes, real-time turbidimetry, addition of cationic polymers to the reaction mixture, polyacrylamide gel-based microchambers, lateral flow dipsticks, fluorescence resonance energy transfer (FRET), enzyme-linked immunosorbent assays and nanoparticle-based colorimetric tests have been utilized for this purpose. In this paper, we reviewed the best-known techniques for evaluation of LAMP amplicons and their applications in molecular biology beside their advantages and deficiencies. Regarding the properties of each technique, the development of innovative prompt, cost-effective and precise molecular detection methods for application in the broad field of cancer research may be feasible.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.398.1-398.1
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• 2014

The $Cu_2ZnSnSe_4$ (CZTSe) thin films solar cell is one of the next generation candidates for photovoltaic materials as the absorber of thin film solar cells because it has optimal bandgap (Eg=1.0eV) and high absorption coefficient of $10^4cm^{-1}$ in the visible length region. More importantly, CZTSe consists of abundant and non-toxic elements, so researches on CZTSe thin film solar cells have been increasing significantly in recent years. CZTSe thin film has very similar structure and properties with the CIGS thin film by substituting In with Zn and Ga with Sn. In this study, As-deposited CZTSe thin films have been deposited onto soda lime glass (SLG) substrates at different deposition condition using Pulsed Laser Deposition (PLD) technique without post-annealing process. The effects of deposition conditions (deposition time, deposition temperature) onto the structural, compositional and optical properties of CZTSe thin films have been investigated, without experiencing selenization process. The XRD pattern shows that quaternary CZTSe films with a stannite single phase. The existence of (112), (204), (312), (008), (316) peaks indicates all films grew and crystallized as a stannite-type structure, which is in a good agreement with the diffraction pattern of CZTSe single crystal. All the films were observed to be polycrystalline in nature with a high (112) predominant orientation at $2{\theta}{\sim}26.8^{\circ}$. The carrier concentration, mobility, resistivity and optical band gap of CZTSe thin films depending on the deposition conditions. Average energy band gap of the CZTSe thin films is about 1.3 eV.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.10a
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• pp.56-56
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• 1999

For advanced TFT-LCD manufacturing processes, dry etching of thin-film layers(a-Si, $SiN_x$, SID & gate electrodes, ITO etc.) is increasingly preferred instead of conventional wet etching processes. To dry etch Al gate electrode which is advantageous for reducing propagation delay time of scan signals, high etch rate, slope angle control, and etch uniformity are required. For the Al gate electrode, some metals such as Ti and Nd are added in Al to prevent hillocks during post-annealing processes in addition to gaining low-resistivity($<10u{\Omega}{\cdot}cm$), high performance to heat tolerance and corrosion tolerance of Al thin films. In the case of AI-Nd alloy films, however, low etch rate and poor selectivity over photoresist are remained as a problem. In this study, to enhance the etch rates together with etch uniformity of AI-Nd alloys, magnetized inductively coupled plasma(MICP) have been used instead of conventional ICP and the effects of various magnets and processes conditions have been studied. MICP was consisted of fourteen pairs of permanent magnets arranged along the inside of chamber wall and also a Helmholtz type axial electromagnets was located outside the chamber. Gas combinations of $Cl_2,{\;}BCl_3$, and HBr were used with pressures between 5mTorr and 30mTorr, rf-bias voltages from -50Vto -200V, and inductive powers from 400W to 800W. In the case of $Cl_2/BCl_3$ plasma chemistry, the etch rate of AI-Nd films and etch selectivity over photoresist increased with $BCl_3$ rich etch chemistries for both with and without the magnets. The highest etch rate of $1,000{\AA}/min$, however, could be obtained with the magnets(both the multi-dipole magnets and the electromagnets). Under an optimized electromagnetic strength, etch uniformity of less than 5% also could be obtained under the above conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.211-214
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• 2004

In the present study, the effect of SIDT (Strain Induced Dynamic Transformation) on the microstructure of medium carbon steels was investigated to develop spheroidized annealing-free steel wire rods. When $0.45\%C$ steels were hot-deformed under the conditions of heavy reduction at low temperatures, a microstructure quite different from conventional ferrite-pearlite structure was obtained. It was considered that this ferrite-cementite microstructure was obtained because very small retained austenite grains existing between fine SIDT ferrites prefer to transform to cementite and ferrite instead of pearlite during cooling. Through the present study, $0.45\%C$ steels containing ferrite-cementite (FC) structure instead of ferrite-pearlite structure was obtained in as-rolled state by introducing SIDT. The specimen containing the FC structure was much softer than that containing conventional ferrite-pearlite structure. Therefore, it is concluded that deforming medium carbon steels under the conditions of SIDT is a very powerful method to obtain soft steel wire rods which could be cold-forged without softening heat-treatment

• Korean Journal of Materials Research
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• v.13 no.2
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• pp.69-73
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• 2003

In this work, $IrO_2$thin films as bottom electrode of ferroelectric capacitors were deposited and characterized. The $IrO_2$films deposited in the conditions of 25, 40 and 50% oxygen ambient by sputtering method were annealed at 600, 700 and $800^{\circ}C$, respectively. It was found that the crystallinity and the surface morphology of $IrO_2$films affected the surface properties and electrical properties of SBT thin films prepared by the MOD method. With increasing temperature, the crystallinity and the roughness of $IrO_2$films were also increasing. This increasing of roughness degraded the surface properties and electrical properties of SBT films. We found an optimum condition of $IrO_2$films as bottom electrode for ferroelectric capacitor at 50% oxygen ambient and $600^{\circ}C$ annealing temperature. Electrical characterizations were performed by using$ IrO_2$bottom electrodes grown at an optimum conditions. The remanent polarization ($P_{r}$) of the Pt/SBT/$IrO_2$/$SiO_2$/Si structure was 2.75 $\mu$C/$\textrm{cm}^2$ at an applied voltage of 3 V. The leakage current density was $1.06${\times}$10^{-3}$ A/$\textrm{cm}^2$ at an applied voltage of 3 V.