• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.179-179
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• 2012

Low pressure radio-frequency glow discharges are investigated using theoretical modeling and various experimental diagnostic methods. In the calculations, global models and transformer models are developed to understand the chemical kinetics as well as the electrical properties such as the effective collision frequency, the heating mechanism and the power transferred to the plasma electrons. In addition, Boltzmann equation solver is used to compensate the effect of the electron energy distribution function (EEDF) shape in the global model, and the general expression of energy balance for non-Maxwellian electrons is developed. In the experiments, a number of traditional plasma diagnostic methods are used to compare with calculated results such as Langmuir probe, optical emission spectroscopy (OES), optical absorption spectroscopy (OAS) and two-photon absorption laser-induced fluorescence (TALIF). These theoretical and experimental methods are applied to understand several interesting phenomena in low pressure ICP discharges. The chemical and physical properties of low pressure ICP discharges are described and the applications of these methods are discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.227-227
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• 2011

최근 ECR (Electron Cyclotron Resonance) 가열에 의한 플라즈마 소스는 고밀도 플라즈마를 유지하면서 고진공 운전을 동시에 만족시켜 다양한 플라즈마 응용 분야에서 많은 관심을 받고 있다. 그 중 HNB (Hyperthermal Neutral Beam)를 이용한 플라즈마 소스에 있어서 ECR 플라즈마 소스는 고진공에서도 높은 플라즈마 밀도를 유지할 수 있기 때문에 기존의 HNB 플라즈마 소스인 ICP (Inductive Coupled Plasma)의 운전압력의 한계점을 해결하여 높은 HNB 방향성(~1mTorr이하)을 가진 고밀도플라즈마를 발생시킬 수 있을 것이라 제안되었다. ECR 플라즈마가 HNB 소스로서 적합하기 위해서는 플라즈마 소스의 대면적화와 균일화가 동시에 이루어져야 한다. 본 연구에서는 이러한 요구에 부합하여 Lisitano coil를 이용한 균일한 대면적 ECR 플라즈마 소스를 설계하였다. 최적의 설계와 진단을 위한 Lisitano Coil antenna 내의 B-field 분포 시뮬레이션과 Langmuir Probe 진단이 이루어졌다.

• Journal of Surface Science and Engineering
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• v.32 no.6
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• pp.703-708
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• 1999

Silicides have been used extensively in ULSI logic device fabrication as contact materials for the active areas as well as the poly- Si gates. NiSi is a promising candidate for submicron device application due to less volume expansion, low formation temperature, little silicon consumption, and large stable processing temperature window. In this report, the microstructure of nickel silicides fabricated with a thermal evaporator has been investigated. We observed systematic transformation of Ni silicides of $Ni_2$Si, NiSi, $NiSi_2$, as annealing temperature increases. All the silicides have been identified by a X-ray diffractometer (XRD). The cross-sectional microstructure of silicides was examined by a transmission electron microscope (TEM) equipped with a energy dispersive spectrometer(EDS). The surface roughness of silicides was measured by scanning probe microscope(SPM). Although we observed thin oxide layer existed at the $Ni/NiSi_{x}$ interface, we fabricated successfully $550\AA$-thick planar Ni-monosilicide at the temperature range of$ 400~700^{\circ}C$.

• Journal of the Semiconductor & Display Technology
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• v.11 no.1
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• pp.1-5
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• 2012

Al doped ZnO (AZO) thin film was deposited by using Facing Target Sputtering (FTS) system. This work examined the properties of AZO thin film as a function of the substrate temperature. The sputtering targets were 4 inch diameter disks of AZO (ZnO : $Al_2O_3$ = 98 : 2 wt.% ). The properties of electrical, structural and optical were investigated by 4-point probe, Hall effect measurement, x-ray diffractometer (XRD), field-emitting scanning electron microscopy (FE-SEM), and UV/VIS spectrometer. The lowest resistivity of films was $5.67{\times}10^{-4}{\Omega}.cm$ and the average optical transmittance of the films was above 85% in the visible range.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.430-430
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• 2011

Graphene, one single atomic layer of graphite, has attracted extensive attention in various research fields since its first isolation from graphite. Application in the future electronics requires better understanding and manipulation of electronic properties of graphene supported on various solid substrates. Here, we present a study on charge doping and morphology of graphene prepared on atomically flat and highly polar mica substrates. Ultra-flat single-layer graphene was prepared by micro-exfoliation of graphite followed by deposition on cleaved mica substrates. Atomic force microscopy (AFM) revealed presence of ultra-thin water films formed in a layer-by-layer manner between graphene and mica substrates. Raman spectroscopy showed that a few angstrom-thick water films efficiently block electron transfer from graphene to mica. Hole doping in graphene caused by underlying mica substrates was also visualized by scanning Kelvin probe microscopy (SKPM).

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.445-449
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• 2008

Micrometer-sized copper (mCu) powders are weakly surface-enhanced Raman scattering (SERS) active by the excitation at 632.8 nm, but nearly ineffective as a SERS substrate at 514.5 nm excitation. The SERS activity of mCu powders at both excitation wavelengths can be increased dramatically by a simple method of the galvanic exchange reaction with AgNO3 in aqueous medium. In this work, the SERS activity of the Ag-exchanged Cu powders (mCu@Ag) has been evaluated by taking a series of Raman spectra using benzenethiol (BT) as the probe molecule. It is clearly confirmed by field emission scanning electron microscopy and X-ray diffractometry that the SERS activity of mCu@Ag powders is, in fact, highly dependent on the extent of galvanic reaction.

• Macromolecular Research
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• v.12 no.5
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• pp.484-489
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• 2004

We have prepared a phenothiazine-based nonlinear optical (NLO) chromophore that displays a fairly high microscopic nonlinearity through intramolecular charge transfer. The phenothiazine unit plays important roles of contributing its high electron donating ability and connecting the resonance pathway through a conjugative effect in the cyclized ring adjacent to the aromatic ring. Theoretical calculations and an absorption spectroscopic study provided useful information concerning the microscopic nonlinearity of the chromophores. We investigated the electro-optic (EO) properties of the guest-host systems in amorphous polycarbonate containing the synthesized chromophores at different concentrations under different poling temperatures. A real-time pole and probe method provided a much greater amount of information regarding how the EO properties can arise and how they can be optimized.

• Journal of the Semiconductor & Display Technology
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• v.16 no.1
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• pp.112-115
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• 2017

ITO thin films were grown on the glass substrate under various oxygen gas flow and substrate temperature by using FTS (Facing Target Sputtering) system. To investigate properties of as-prepared films for transparent electrical devices, we employed four-point probe, UV-VIS spectrometer, X-ray diffractometer (XRD), scanning electron microscopy (SEM), Hall Effect measurement system and Atomic Force Microscope (AFM). As a results, all of prepared samples has high transmittance of over 80 % in the visible range (300-800 nm). Their resistivity increased as a function of oxygen gas flow and substrate temperature due to their crystal structure and oxygen defect in the films. As-prepared films have a resistivity of under $10^{-4}({\Omega}-cm)$.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1138-1139
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• 2006

The present study has shown that the effect of boron and phosphorus in Ni-Cr-Si-X alloy to interfacial reactions and bonding strength of diamond-steel substrate, and the influence of various construction parameters on the formation of the topography of the tool. And these factors are required to making a good brazed tool. The microstructures and phase change of the brazed region were analyzed into SEM, EDS. According to the electron probe microanalysis, while brazing, the chromium present in the brazing alloy segregated preferentially to the surface of the diamond to form a chromium rich reaction product, which was readily wetted by the alloy.

• Journal of Welding and Joining
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• v.35 no.3
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• pp.52-61
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• 2017

Transient liquid phase (TLP) bonding is essential technology to repair micro-cracking on the airfoil of blades and vanes for gas turbines. Understanding of the characteristics of TLP bonding of the superalloys is necessary in the application of the technology for repairing these components. In this study, the focus was on investigating TLP bonding characteristics of ${\gamma}^{\prime}$ precipitation strengthened Ni based superalloy. TLP bonding was carried out with an amorphous filler metal in various bonding conditions, and the microstructural characterization was investigated through optical microscopy (OM) and electron probe micro-analysis (EPMA). The experimantal results explained clearly that bonding temperatures had critical effects on the TLP bonding behaviors, and that isothermal solidication of the joints made at higher temperatures than $1170^{\circ}C$ was controlled by Ti diffusion instead of B.