• Journal of the Korean institute of surface engineering
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• v.46 no.3
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• pp.116-119
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• 2013

To improve the corrosion resistance of an electrogalvanized steel sheet, we deposited magnesium film on it using a vacuum evaporation method and annealed the films at $250-330^{\circ}C$. The zinc-magnesium alloy is consequently formed by diffusion of magnesium into the zinc coating. From the anodic polarization test in 3% NaCl solution, the films annealed at $270-310^{\circ}C$ showed better corrosion resistance than others. In X-ray diffraction analysis, $ZnMg_2$ was detected through out the temperature range, whereas $Mg_2Zn_{11}$ and $FeZn_{13}$ were detected only in the film annealed at $310^{\circ}C$. The depth composition profile showed that the compositions of Mg at $270-290^{\circ}C$ are evenly and deeply distributed in the film surface layer. These results demonstrate that $270-290^{\circ}C$ is a proper temperature range to produce a layer of $MgZn_2$ intermetallic compound to act as a homogeneous passive layer.

• Journal of the Korean Ceramic Society
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• v.53 no.1
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• pp.81-86
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• 2016

The effect of substrate rotation speed on the phase forming behavior and microstructural variation of 8 wt% yttria ($Y_2O_3$) stabilized $ZrO_2$ (8YSZ) coatings as a thermal barrier coating has been investigated. 8YSZ coatings with $100{\sim}200{\mu}m$ thickness were deposited by electron beam-physical vapor deposition onto a super alloy (Ni-Cr-Co-Al) substrate with a bond coating (NiCo-CrAlY). The width of the columnar grains of the 8YSZ coatings increased with increasing substrate rotation speed from 1 to 30 rpm at a substrate temperature range of $900{\sim}950^{\circ}C$. In spite of the different growth behaviors of coatings with different substrate rotation speeds, the phases of each coating were not changed remarkably. Even after post heat treatments with various conditions of the coated specimens fabricated at 20 rpm, only a change of color was noticeable, without any remarkable change in the phase or microstructure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.292-292
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• 2009

OLED(Organic Light Emitting Device)는 LCD(Liquid Crystal Display)의 뒤를 잇는 차세대 디스플레이의 선두주자로서 자체발광형이기 때문에 백라이트 등의 보조광원이 불필요하며, 구동전압이 낮고 넓은 시야각과 빠른 응답속도 등의 특징을 가지고 있다. 또한 플렉서블 기판을 사용할 수 있어 차세대 디스플레이인 플렉서블 디스플레이에 적합하다. 플렉서블한 디스플레이를 만들기 위해서 플라스틱 기판에 OLED 물질을 사용하여 기존에 무겁고, 깨지기 쉬우며, 변형이 불가능한 유리로 만든 소자 보다 더 가볍고 깨지지 않고 변형이 가능한 플렉서블 디스플레이를 제작 할 수 있다. 그러나 플라스틱 기판은 매우 큰 투습율을 가지고 있어 OLED소자에 적용시키면 공기 중의 수분이나 산소와 접촉이 많아져 쉽게 산화되어 소자의 효율 및 수명이 짧아진다. 또한 OLED에 사용되는 유기물도 산소나 수분에 의해 특성이 급격히 저하되기 때문에 산소 및 수분의 차단은 필수적이다. 이러한 단점을 최소화하기 위해서 PECVD(Plasma Enhanced Chemical Vapor Deposition)로 만든 SiON(Silicon Oxynitride) 박막을 차단막(Passivation layer)으로 사용하였다. PECVD를 이용하여 SiON 박막을 증착시킬 때 RF Power, 공정압력, Distance의 변화에 따른 박막의 결정화도, 수분투습도, 광투과도 등의 특성을 FT-IR(Fourier Transform Infrared Spectroscopy), Ellipsometer, UV-visible Spectrophotometer, MOCON를 이용하여 SiON 박막의 특성을 고찰하였다.

• Journal of the Korean institute of surface engineering
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• v.43 no.6
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• pp.266-271
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• 2010

Ternary Mo-Cu-N films were deposited on Si wafer substrates with various copper contents by magnetron sputtering method using Mo target and Cu target in $Ar/N_2$ gaseous atmosphere. As increasing $N_2$ pressure, the microstructure of Mo-N films changed from ${\gamma}-Mo_2N$ of (111) having face-centered-cubic (FCC) structure to $\delta$-MoN of (200) having hexagonal structure. Detailed the microstructures of the Mo-Cu-N coatings were studied by X-ray diffraction, scanning electron microscopy and field emission transmission electron microscope. The results indicated that the incorporation of copper into the growing Mo-N coating led to the $Mo_2N$ and MoN crystallites were more well-distributed and refined and the copper existed in grain boundary. Ternary Mo-Cu-N films had a composite microstructure of the nanosized crystal crystalline ${\gamma}-Mo_2N$ and $\delta$-MoN surrounded by amorphous $Cu_3N$ phase.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.4
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• pp.123-130
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• 2013

Zirconia is well known in industrial applications for its mechanical characteristics. DLC (diamond-like carbon) have high elastic modulus, high electric resistivity, high dielectric constant, high wear resistance, low friction coefficient, bio compatibility, chemically inert and thermally stable. Because of all these physical and chemical properties these types of coatings have become key procedure for thin coating. Friction coefficient of DLC films is already evaluated and the current work is a further advancement by calculating the fracture toughness and wear resistance of these coatings. In the present study DLC thin film coatings are developed on $ZrO_2$ alloy surface using Plasma Enhanced Chemical Vapor Deposition (PECVD) method. Vicker hardness test is employed and it was concluded that, DLC coatings increase the Vickers hardness of ceramics.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.484-484
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• 2013

기존 진단용 Digital X-ray Detector이 직접방식에서는 a-Se (Amorphous Selenium)이 대중화되었지만 고전압을 인가하여야한다는 점과 그로 인한 물질 자체의 Life time 감소 등 여러 단점들 때문에 기타 후보물질들로 HgI2, PbI2, PbO, CdTe, CdZnTe가 연구 되고 있다. 이러한 후보 물질들 중 본 연구에서는 PVD (Physical Vapor Deposition)방식을 이용하여 Polycrystalline CdTe 박막을 제작하고 특성 향상을 위해 유전물질을 Passive layer와 Protect layer로써 증착하였다. 또한 유전체층의 위치에 따른 특성 분석을 위해 제작된 박막은 FE-SEM (Field Emission Scanning Electron Microscope), XRD (X-ray Diffraction)을 통해 구조적인 특성을 확인하였다. 그리고 입사되는 X-ray 선량에 의해 생성되는 전기적 특성을 분석하였다, 그 결과 박막의 Grain Size는 약 $5{\mu}M$이며 (111)방향의 주 peak를 띄는 Poly CdTe형태로 증착된 것을 확인하였다. 전기적인 신호 결과 Passive layer와 Protect layer를 증착한 박막 모두 Darkcurrent가 감소된 것을 확인하였다. 또한 Sensitivity 측정 결과 Passive layer를 삽입한 경우 신호 값이 감소하였으며 Protect layer를 삽입한 경우 신호 값의 변화가 일어나지 않았다. 그러므로 Protect layer를 등착한 박막의 경우 SNR이 현저히 높아지는 결과를 낳았다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.470-473
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• 2001

In this study, 70/30 mol% P(VDF-TrFE) copolymer thin films were prepared by physical vapor deposition, and dielectric properties with frequency were investigated. From results of TA(Thermal Analysis), the Curie transition temperature and melting temperature were observed at 118.8$^{\circ}C$ and 146$^{\circ}C$, respectively. Therefore, while thin films were prepared, the substrate temperature was varied from 30$^{\circ}C$ to 90$^{\circ}C$. The dielectric constant decreased with increasing frequency. At measuring frequency of 1kHz, the relative dielectric constant increased from 3.643 to 23.998 with increasing substrate temperature from 30$^{\circ}C$ to 90$^{\circ}C$. As a result of dielectric loss factor, ${\alpha}$-relaxation and ${\beta}$-relaxation were observed near at 100Hz and 1MHz, respectively. And the magnitude of ${\alpha}$-relaxation decreased and that of ${\beta}$-relaxation increased with increasing substrate temperature.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.271-284
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• 1999

As a semiconductor material for electronic devices operated under extreme environmental conditions, silicon carbides (SiCs) have been intensively studied because of their excellent electrical, thermal and other physical properties. The growth characteristics of single-crystalline 4H-SiC homoepitaxial layers grown by a thermal chemical vapor deposition (CVD) were investigated. Especially, the successful growth condition of 4H-SiC homoepitaxial layers using a SiC-uncoated graphite susceptor that utilized Mo-plates was obtained. The CVD growth was performed in an RF-induction heated atmospheric pressure chamber and carried out using off-oriented substrates prepared by a modified Lely method. In order to investigate the crystallinity of grown epilayers, Nomarski optical microscopy, Raman spectroscopy, photoluminescence(PL), scanning electron microscopy (SEM) and other techniques were utilized. The best quality of 4H-SiC homoepitaxial layers was observed in conditions of growth temperature 1500$^{\circ}C$ and C/Si flow ratio 2.0 of C3H3 0.2sccm & SiH4 0.3sccm. The growth rate of epilayers was about 1.0$\mu\textrm{m}$/h in the above growth condition.

• Progress in Superconductivity and Cryogenics
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• v.17 no.2
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• pp.1-17
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• 2015

$MgB_2$ thin films with superior superconducting properties are very promising for superconducting magnets, electronic devices and coated conductor electric power applications. A clear understanding of flux pinning mechanism in $MgB_2$ films could be a big aid in improving the performance of $MgB_2$ by the enhancement of $J_c$. The fabrication advancement and the understanding of flux pinning mechanism of $MgB_2$ thin and thick films fabricated by using hybrid physical-chemical vapor deposition (HPCVD) are reviewed. The distinct kind of $MgB_2$ films, such as single-crystal like $MgB_2$ thin films, $MgB_2$ epitaxial columnar thick films, and a-axis-oriented $MgB_2$ films are included for flux pinning mechanism investigation. Various attempts made by researchers to improve further the flux pinning property and $J_c$ performance by means of doping in $MgB_2$ thin films by using HPCVD are also summarized.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.11
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• pp.953-957
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• 2002

Single crystal 3C-SiC (cubic silicon carbide) thin-films were deposited on Si(100) wafer up to the thickness of 4.3 ${\mu}{\textrm}{m}$ by APCVD (atmospheric pressure chemical vapor deposition) method using HMDS (hexamethyildisilane; ｛CH$_{3}$｝$_{6}$ Si$_{2}$) at 135$0^{\circ}C$. The HMDS flow rate was 0.5 sccm and the carrier gas flow rate was 2.5 slm. The HMDS flow rate was important to get a mirror-like crystal surface. The growth rate of the 3C-SiC film was 4.3 ${\mu}{\textrm}{m}$/hr. The 3C-SiC epitaxial film grown on Si(100) wafer was characterized by XRD (X-ray diffraction), AFM (atomic force microscopy), RHEED (reflection high energy electron diffraction), XPS (X-ray photoelecron spectroscopy), and Raman scattering, respectively. Two distinct phonon modes of TO (transverse optical) near 796 $cm^{-1}$ / and LO (longitudinal optical) near 974$\pm$1 $cm^{-1}$ / of 3C-SiC were observed by Raman scattering measurement. The heteroepitaxially grown film was identified as the single crystal 3C-SiC phase by XRD spectra (2$\theta$=41.5。).).