• 한국표면공학회지
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• 제44권5호
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• pp.226-231
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• 2011

Graphene was coated on STS 316L by electro spray coating method to improve its properties of corrosion resistance and contact resistance. Exfoliated graphite (graphene) was made of the graphite by chemical treatment. Graphene is distributed using dispersing agent, and STS 316L was coated with diffuse graphene solution by electro spray coating method. The structure of the exfoliated graphite was analyzed using XRD and the coating layer of surface was analyzed by using SEM. Analysis showed that multi-layered graphite structure was destroyed and it was transformed into fine layers graphene structure. And the result of SEM analysis on the surface and the cross section, graphene layer was uniformly formed with 3~5 ${\mu}m$ thickness on the surface of substrate. Corrosion resistance test was applied in the corrosive solution which is similar to the PEM fuel cell stack inside. And interfacial contact resistance test was measured to simulate the internal operating conditions of PEM fuel cell stack. The results of measurements show that stainless steel coated with graphene was improved in corrosion resistance and surface contact resistance than stainless steel without graphene coating layer.

• 한국세라믹학회지
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• 제41권1호
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• pp.30-35
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• 2004

스크린 인쇄법 및 PZT sol 처리의 복합공정을 적용하여 $30{\mu}m$ 두께의 PMW-PZT 후막을 Pt/$TiO_2$/$SiN_x$Si 기판위에 제작하였다. 그 결과 PZT sol 처리 횟수가 증가함에 따라 후막의 소결 밀도가 증가하고 전기적, 압전 특성의 증진되는 것을 관찰할 수 있었다. $800^{\circ}C$에서 소결한 10회 sol 처리한 PMW-PZT 후막은 745의 유전상수 및 155 pC/N의 $d_33$ 값을 나타내었다.

• 한국전자파학회논문지
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• 제18권3호
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• pp.298-304
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• 2007

본 논문에서는 다중대역 (GSM850, EGSM, DCS1800, USPCS, W-CDMA)에서 동작하는 안테나에 대해 제안하고 있다. 상기 안테나는 상용 소프트웨어인 HFSS 3-D 시뮬레이터로 설계되었으며, FR-4(비유전율 4.4) PCB 기판위에 원형 도통관(via)과 금속 패턴으로 이루어진 미앤더 가지 구조로 구성되어 있다. 특히 이 안테나에는 전체 대역폭의 성능 향상을 위해 간극 급전 구조를 사용하였다. 디자인된 안테나는 PCB 공정을 이용하여 제작되었고, 네트웍 분석기와 테스트 챔버를 사용하여 측정하였다. 폭 8 mm에 높이 20 mm, 두께 3.2 mm의 크기를 차지하는 제작된 안테나는 다중 대역 이동 통신 단말기의 내부에 장착하여 사용할 수 있다.

• 한국통신학회논문지
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• 제42권1호
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• pp.286-290
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• 2017

본 논문에서는 노치 대역 특성을 갖는 UWB 육각형 패치 안테나를 제안하였다. 노치 대역은 WLAN의 5.15 ~ 5.85 GHz 대역이며, 원형 슬릿을 패치에 삽입하여 유도하였다. 제안된 안테나의 임피던스 대역폭은 3.1 ~ 11.85 GHz 대역으로 UWB 통신 시스템의 대역폭을 만족하였으며, 5.2 ~ 5.8 GHz 대역에서 노치 대역 특성을 보였다. 안테나의 방사패턴은 XZ-plane에서 $0^{\circ}$와 $180^{\circ}$에서 지향성의 패턴을 보이며, YX-plane에서 무지향성 패턴을 보인다. 또한, 주파수가 증가할수록 안테나 이득도 증가하며, 노치 대역 구간에서는 안테나 이득이 감소하였다. 제안된 안테나는 두께 1.62 mm, 손실 탄젠트 0.0035, 유전율 4.5를 갖는 TRF-45 기판에 설계되었으며, 설계는 Ansys사의 HFSS를 사용하였다.

• 한국전기전자재료학회논문지
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• 제18권11호
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• pp.1043-1047
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• 2005

To investigate the electrical properties of the ZnO films which are interested in the next generation of short wavelength LEDs and Lasers, our ZnO thin films were deposited by RF sputtering system. At sputtering process of ZnO thin films, substrate temperature, work pressure respectively is $300^{\circ}C$ and 5.2 mTorr, and the purity of target is ZnO 5N. The thickness of ZnO thin films was about $2.1\;{\mu}m$ at SEM analysis after sputtering process. Phosphorus (P) and arsenic (As) were diffused into the undoped ZnO thin films sputtered by RF magnetron sputtering system in ampoule tube which was below $5\times10^{-7}$ Torr. The dopant sources of phosphorus and arsenic were $Zn_3P_2$ and $ZnAs_2$. Those diffusion was perform at 500, 600, and $700^{\circ}C$ during 3 hr. We found the diffusion condition of the conductive ZnO films which had n- and p-type properties. Our ZnO thin film has not only very high carrier concentration of above $10^{17}/cm^3$ but also low resistivity of below $2.0\times10^{-2}\;{\Omega}cm$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.163-166
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• 2002

We investigated structural and electrical properties of Metal-Oxide-Semiconductor(MOS) structure using Hafnium $oxide(HfO_{2})$ as high-k gate dielectric material. $HfO_{2}$ films are ultrathin gate dielectric material witch have a thickness less than 2.0nm， so it is spotlighted to be substituted $SiO_{2}$ as gate dielectric material. In this paper We have grown $HfO_{2}$ films with pt electrode on P-type Silicon substrate by RF magnetron sputtering system using $HfO_{2}$ target and oserved the property of semiconductor-oxide interface. Using pt electrode, it is necessary to be annealed at ${300^{\circ}C}$. This process is to increase an adhesion ratio between $HfO_{2}$ films with pt electrode. In film deposition process, the deposition time of $HfO_{2}$ films is an important parameter. Structura1 properties are invetigated by AES depth profile, and electrical properties by Capacitance-Voltage characteristic. Interface trap density are measured to observe the interface between $HfO_{2}$ with Si using High-frequency(1MHz) C-V and Quasi - static C-V characteristic.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 제5회 영호남 학술대회 논문집
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• pp.85-88
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• 2003

$Sr_xBa_{1-x}Nb_2O_6$(SBN, $025{\leq}x{\leq}0.75$) ceramic is a ferroelectric material with tetragonal tungsten bronze (TTB) type structure, which has a high pyroelectric coefficient and a nonlinear electro-optic coefficient value. In spite of its advantages, SBN has not been investigated well compared to other ferroelectric materials with perovskite structure. In this study, SBN thin film was manufactured by ion beam sputtering technique using the prepared SBN target in Ar/$O_2$ atmosphere. SBN30 thin film of 500 ${\AA}$ was pre-deposited as a seed layer on Pt(l00)/$TiO_2$/$SiO_2$/Si substrate followed by SBN60 deposition up to 4500 ${\AA}$ in thickness. SBN60/SBN30 layer was deposited at different Oxygen amount of 0, 8.1, 17, and 31.8 sccm, respectively. The crystallinity and orientation behavior as well as electric properties of SBN60/SBN30 multi-layer were examined. The deposited layer was uniform and the orientation was shown primarily along (001) plane from XRD pattern. The crystal structure and the electric properties depended on the Oxygen amount, heating temperature and was the best at O2 = 8.1 seem, $750^{\circ}C$. In electric properties of Pt/SBN60/SBN30/Pt thin film capacitor prepared, the remnant polarization (2Pr) value was 13 ${\mu}C/cm^2$, the coercive field (Ec) 75 kV/cm, and the dielectric constant 1492, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.9-9
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• 2009

Coated conductor is required to have good critical current property for high efficiency of electric power applications. Until now, long coated conductor does not show high Jc over 3 MA/$cm^2$ in thick superconducting layer because of texture degradation by thick superconducting layer. In this study, in order to overcome this issue, thicker superconducting layer was deposited with optimized conditions to reduce the degradation of critical current density. SmBCO superconducting coated conductor was deposited with 1~3 um of thickness at $750\sim850^{\circ}C$ under 15~20 mTorr of oxygen partial pressure using batch type EDDC( evaporation using drum in dual chamber). The buffered substrate for superconducting layer deposition was used IBAD-MgO template with the architecture of $LaMnO_3/MgO/Y_2O_3/Al_2O_3$/Hastelloy. After fabrication of coated conductor, critical current was measured by 4-prove method under self-magnetic field and 77K. In addition, surface morphology and texture were analyzed by SEM and XRD, respectively. 3 um thick SmBCO coated conductor shows highest $I_C$ values of 638A/cm-w in 1 m long in the world.

• 한국전자파학회논문지
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• 제25권1호
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• pp.39-46
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• 2014

본 논문에서는 On-Board Broadband 특성을 갖는 2.4 GHz Inverted-L 안테나를 제안하였다. 안테나는 시스템 보드에 Inverted-L 안테나를 설계하였으며, 공통 모드와 차동 모드를 형성하도록 스터브를 설계하여 안테나의 리액턴스를 조정하여 대역폭을 개선하였다. 시스템 크기는 $80mm{\times}60mm$이고, 안테나 영역은 $30mm{\times}60mm$로 제한하였으며, 기판은 두께가 0.8 mm이고, 유전율이 4.4인 FR4를 사용하였다. 실험 결과, 대역폭은 17.2~24.1 %이고, 이득은 3.01~4.71 dB이며, 방사 패턴은 전방향 특성의 결과를 얻었다. 본 논문의 결과를 적용함으로써 휴대 단말기의 가격경쟁력과 생산효율을 향상시킬 수 있다.

• Nuclear Engineering and Technology
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• 제45권5호
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• pp.683-688
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• 2013

Candidate coating materials for re-usable metallic nuclear fuel crucibles, TaC, TiC, ZrC, $ZrO_2$, and $Y_2O_3$, were plasmasprayed onto a niobium substrate. The microstructure of the plasma-sprayed coatings and thermal cycling behavior were characterized, and U-Zr melt interaction studies were carried out. The TaC and $Y_2O_3$ coating layers had a uniform thickness, and high density with only a few small closed pores showing good consolidation, while the ZrC, TiC, and $ZrO_2$ coatings were not well consolidated with a considerable amount of porosity. Thermal cycling tests showed that the adhesion of the TiC, ZrC, and $ZrO_2$ coating layers with niobium was relatively weak compared to the TaC and $Y_2O_3$ coatings. The TaC and $Y_2O_3$ coatings had better cycling characteristics with no interconnected cracks. In the interaction studies, ZrC and $ZrO_2$ coated rods showed significant degradations after exposure to U-10 wt.% Zr melt at $1600^{\circ}C$ for 15 min., but TaC, TiC, and $Y_2O_3$ coatings showed good compatibility with U-Zr melt.