• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.399-399
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• 2013

Metal silicides는 Si 기반의microelectronic devices의 interconnect와 contact 물질 등에 사용하기 위하여 그 형성 mechanism과 전기적 특성에 대한 연구가 많이 이루어지고 있다. 이 중 Rare-earth(RE) silicides는 저온에서 silicides를 형성하고, n-type Si과 낮은 Schottky Barrier contact (~0.3 eV)을 이룬다. 또한 낮은 resistivity와 Si과의 작은 lattice mismatch, 그리고 epitaxial growth의 가능성, 높은 thermal stability 등의 장점을 갖고 있다. RE silicides 중 ytterbium silicide는 가장 낮은 electric work function을 갖고 있어 n-channel schottky barrier MOSFETs의 source/drain으로 주목받고 있다. 또한 Silicon 기반의 CMOSFETs의 성능 향상 한계로 인하여 germanium 기반의 소자에 대한 연구가 이루어져 왔다. Ge 기반 FETs 제작을 위해서는 낮은 source/drain series/contact resistances의 contact을 형성해야 한다. 본 연구에서는 저접촉 저항 contact material로서 ytterbium germanide의 가능성에 대해 고찰하고자 하였다. HRTEM과 EDS를 이용하여 ytterbium germanide의 미세구조 분석과 면저항 및 Schottky Barrier Heights 등의 전기적 특성 분석을 진행하였다. Low doped n-type Ge (100) wafer를 1%의 hydrofluoric (HF) acid solution에 세정하여 native oxide layer를 제거하고, 고진공에서 RF sputtering 법을 이용하여 ytterbium 30 nm를 먼저 증착하고, 그 위에 ytterbium의 oxidation을 방지하기 위한 capping layer로 100 nm 두께의 TiN을 증착하였다. 증착 후, rapid thermal anneal (RTA)을 이용하여 N2 분위기에서 $300{\sim}700^{\circ}C$에서 각각 1분간 열처리하여 ytterbium germanides를 형성하였다. Ytterbium germanide의 미세구조 분석은 transmission electron microscopy (JEM-2100F)을 이용하였다. 면 저항 측정을 위해 sulfuric acid와 hydrogen peroxide solution (H2SO4:H2O2=6:1)에서 strip을 진행하여 TiN과 unreacted Yb을 제거하였고, 4-point probe를 통하여 측정하였다. Yb germanides의 면저항은 열처리 온도 증가에 따라 감소하다 증가하는 경향을 보이고, $400{\sim}500^{\circ}C$에서 가장 작은 면저항을 나타내었다. HRTEM 분석 결과, deposition 과정에서 Yb과 Si의 intermixing이 일어나 amorphous layer가 존재하였고, 열처리 온도가 증가하면서 diffusion이 더 활발히 일어나 amorphous layer의 두께가 증가하였다. $350^{\circ}C$ 열처리 샘플에서 germanide/Ge interface에서 epitaxial 구조의 crystalline Yb germanide가 형성되었고, EDS 측정 및 diffraction pattern을 통하여 안정상인 YbGe2-X phase임을 확인하였다. 이러한 epitaxial growth는 면저항의 감소를 가져왔으며, 열처리 온도가 증가하면서 epitaxial layer가 증가하다가 고온에서 polycrystalline 구조의 Yb germanide가 형성되어 면저항의 증가를 가져왔다. Schottky Barrier Heights 측정 결과 또한 면저항 경향과 동일하게 열처리 증가에 따라 감소하다가 고온에서 다시 증가하였다.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.77-82
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• 2014

Stretchable electrodes are focused due to many demands for soft electronics. One of the candidates, carbon black composites have advantages of low cost, easy processing and decreasing resistivity in a certain range during stretching. However, the electrical conductivity of carbon black composites is not enough for electronic devices. Graphene is 2-dimensional nanostructured carbon based material which shows good electrical properties and flexibility. They may help to improve electrical conductivity of the carbon black composites. In this study, graphene was added to a carbon black electrode to enhance electrical properties and investigated. Electrical resistivity of graphene added carbon electrode decreased comparing with that of carbon black electrode because graphene bridged non-contacting carbon black aggregates to strengthen the conductive network. Also graphene reduced an increase in the resistance of the carbon black electrode applied to strain because they connected gap of separated carbon black aggregates and aligned along the stretching direction at the same time. In conclusion, an addition of graphene to carbon black gives two benefits on the electrical properties of carbon black composite as a stretchable electrode.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.10
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• pp.495-499
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• 2004

Characteristics of ohmic Ni/Si/Ni contacts to n-type 4H-SiC are investigated systematically. The ohmic contacts were formed by annealing Ni/Si/Ni sputtered sequentially The annealings were performed at 950℃ using RTP in vacuum ambient and N₂ ambient, respectively. The specific contact resistivity(p/sub c/), sheet resistance(R/sub s/), contact resistance (R/sub c/) transfer length(L/sub T/) were calculated from resistance(R/sub T/) versus contact spacing(d) measurements obtained from TLM(transmission line method) structure. While the resulting measurement values of sample annealed at vacuum ambient were p/sub c/ = 3.8×10/sup -5/Ω㎠, R/sub c/ = 4.9 Ω and R/sub T/ = 9.8 Ω, those of sample annealed at N₂ ambient were p/sub c/ = 2.29×10/sup -4/Ω㎠, R/sub c/ = 12.9 Ω and R/sub T/ = 25.8 Ω. The physical properties of contacts were examined using XRD 3nd AES. The results showed that nickel silicide was formed on SiC and Ni was migrated into SiC. This result indicates that Ni/Si/Ni ohmic contact would be useful in high performance electronic devices.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.41-44
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• 2008

본 연구에서는 고분자 전해질 연료전지용 금속분리판의 전기화학적 부식을 방지하기 위한 금속 첨가 DLC(Diamond-like-carbon) 표면처리 방법을 개발하였으며, stainless steel 304를 모재로 하여 텅스텐 첨가 DLC, 티타늄 첨가 DLC, 몰리브덴 첨가 DLC 금속분리판을 제작하였다. 제작된 금속분리판을 이용하여 내구성 평가,전기화학적 부식 특성, 성능평가 및 접촉저항 특성 등을 평가하였다. 전기화학적 부식특성의 경우 각각의 분리판에 대해 6.69, 1.2, 1.0 ${\mu}A/cm^2$로 모재인 STS 304의 25 ${\mu}A/cm^2$의 부식전류밀도에 비해 우수한 부식특성을 보였다. 또한 초기 성능에서 몰리브덴 첨가 DLC 분리판의 경우 300 mA/$cm^2$에서 0.757 V로 측정되었으며, 이는 graphite 분리판 측정 결과인 0.758 V와 유사한 성능을 보였다. 또한 내구성 평가에서 초기 성능 대비 성능 감소율이 10% 감소하는데 소요된 시간은 graphite 분리판의 경우 2,000시간으로 나타났으며, 몰리브덴 첨가 DLC 분리판의 경우 1,700시간으로 측정되었다. 1,500시간 까지의 성능 감소율은 grphite,텅스텐 첨가DLC,티타늄 첨가DLC, 몰리브덴 첨가 DLC 분리판 순으로 각각에 대해 37.7, 60.3, 92.8, 45.7 ${\mu}V$/hr로 나타났다.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.1 no.2
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• pp.62-69
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• 1987

In the thesis research on the C.T.I for the borne by tracking phenolic resin, electolytic errosion appearance of electrode materials causes the part of electrode to increase the failure of tracking. $\circled1$ In the material of insulation in which C.T.I has 350 degree or so, We can obtain the constant value by Cu.Zn electrode than Pt electrode. $\circled2$ C.T.I value has noting to do with resistance rate of electrolyte. $\circled3$ As the contact angle of interface grow, the starting electric stress of corona and the value of C.T.I increase.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.4
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• pp.147-151
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• 2002

The resistances of metal2 contact to metall and poly Si are checked by various RF etch conditions in terms of pre-cleaning. The changes of resistance are evaluated by statistical analysis method(SAS) for the AC bias power, coil power and RF target. The contact area on poly Si is shown by TEM image and the distributions of contact resistance according to ar etch target and RTP are investigated. The RTP groups have larger variations than normal RF etch targets. When the RF etch target becomes lower and coil power becomes higher, the resistances of metal2 contact to metals and poly Si have lower contact resistance. But the condition of AC bias power did not satisfied low meta12 contacts resistance for metall and poly Si simultaneously. The R-square of ststistical analysis was 0.98 for resistances of meta12 contact to poly Si and 0.87 for resistances of meta12 contact to metall.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.116-116
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• 2000

질화물 반도체는 LED, LD, Transistor, 그리고 Photodetector 등 광소자 및 전자소자를 실현할 수 있는 소재로써 최근에 각광 받고 있으며, 또한 국·내외적으로 연구가 활발히 진행되고 잇다. 질화물 발광 다이오드 제작에는 소자의 효율과 수명시간의 향상을 위하여 질화물 반도체와 금속과의 접합시 고 품질의 오믹 접합이 필수적이다. 특히 p-형 GaN의 경우에는 높은 정공 농도를 갖는 p-형 GaN를 얻기가 어렵고 GaN의 일함수에 비하여 높은 일함수를 갖는 금속이 없기 때문에 매우 낮은 접합 저항을 가지며 안정성이 매우 우수한 금 접합을 얻기가 어렵다고 알려져 있다. 또한, GaN 계열의 발광 다이오드는 일반적으로 표면 발광 다이오드 형태로 제작되기 때문에 p-형 GaN 층의 오믹 접촉으로 사용되는 금속의 전기적 특성뿐만 아니라 발광 다이오드의 활성층에서 발광되어 나오는 빛에 대한 투과도 또한 우수하여야 발광 다이오드의 효율이 우수해진다. 본 연구에서는 p-형 GaN층의 접합 금속으로 Pt(80nm)과 Ni(5nm)/Au(7nm)를 사용하여 InGaN/GaN 다중양자우물 구조의 발광 다이오드를 제작하여 전기적 특성 및 발광효율을 측정하였다. 그리고, Pt(80nm)과 p-형 GaN와의 접합시 온도 변화에 따른 전기적 특성을 TLM 방법으로 조사하고, 가시광선 영역에서의 빛에 대한 투과도를 UV/VIS spectrometer, X-ray reflectivity, 그리고 Atomic Force Microscopy 등을 이용하여 분석하였다.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.4
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• pp.9-16
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• 2014

Electrode contact resistance is a crucial factor in physiological measurements and can be an accuracy limiting factor to perform electrical impedance measurements. The electrical bio-impedance values can be calculated by the conductivity and permittivity of underlying tissue using implant electrode in human skin. In this study we focus on detecting physiological changes in the human skin layers such as the sebum layer, stratum corneum layer, epidermis layer, dermis layer, subcutaneous fat and muscle. The aim of this paper is to obtain optimal design for implantable electrode at subcutaneous fat layer through the simulation by finite element methods(FEM). This is achieved by evaluating FEM simulations geometrically for different electrodes in length(50 mm, 70 mm), in shape(rectangle, round square, sexangle column), in material(gold) and in depth(22.325 mm) based on the information coming from the subcutaneous fat layer. In bio-impedance measurement experiments, according to electrode shapes and applied voltage, we have ascertained that there was the highest difference of bio-impedance in subcutaneous fat layer. The methodology of simulation can be extended to account for different electrode designs as well as more physical phenomena that are relevant to electrical impedance measurements of skin and their interpretation.

• Journal of Adhesion and Interface
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• v.12 no.3
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• pp.88-93
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• 2011

Optimal dispersion and fabrication conditions of carbon nanotube (CNT) embedded in phenolic resin were determined by electrical resistance measurement; and interfacial property was investigated between plasma treated carbon fiber and CNT-phenolic composites by electro-micromechanical techniques. Wettability of carbon fiber was improved significantly after plasma treatment. Surface energies of carbon fiber and CNT-phenolic nanocomposites were measured using Wilhelmy plate technique. Since surface activation of carbon fiber, the advancing contact angle decreased from $65^{\circ}$ to $28^{\circ}$ after plasma treatment. It was consistent with static contact angle results of carbon fiber. Work of adhesion between plasma treated carbon fiber and CNT-phenolic nanocomposites was higher than that without modification. The interfacial shear strength (IFSS) and apparent modulus also increased with plasma treatment of carbon fiber.

• Composites Research
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• v.25 no.3
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• pp.76-81
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• 2012

Atmospheric pressure plasma treatment on carbon nanotube (CNT) surfaces was performed to modify reinforcement effect and interfacial adhesion of carbon fiber reinforced CNT-phenolic composites. The surface changes occurring on CNT treated with plasma were analyzed by using Fourier transform infrared spectroscope (FT-IR). The significant improvement of wettability on CNT was confirmed by static contact angle test after plasma treatment. Such plasma treatment resulted in a decrease in the advancing contact angle from $118^{\circ}$ to $60^{\circ}$. The interfacial adhesion between carbon fiber and CNT-phenolic composites increased by plasma treatment based on apparent modulus test results during quasi-static tensile strength. Furthermore, the proposed database offers valuable knowledge for evaluating interfacial shear strength (IFSS).