• 대한기계학회논문집
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• 제16권9호
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• pp.1632-1642
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• 1992

본 연구에서는 방전가공(electric disharge machining, EDM) 또는 공기연마 분사기(air-abrasive jet machine, AJM) 가공에 의하여 인장 시험편 또는 외팔보 시험 편에 구멍깊이를 증가시켜 가면서 구멍을 뚫었다. 여기에서 방저가공(EDM)을 채택한 것은 구멍깊이를 직접 계측하는 것이 가능하여 구멍깊이 측정 오차에 기인하는 잔류응 력 측정오차를 최소화 할 수 있기 때문이며, 공기연마 분사기를 채택한 것은 구멍을 뚫는 동안 가공응력을 유발시키지 않기 때문이었다. 위 인장 시험편 또는 외팔보 시 험편을 이용하여 균일한 응력장과 두께 방향으로 변하는 선형적 구배응력장을 구현하 고, 이 때 각각 구멍깊이가 다른 원통형 막힘 구멍으로 부터 이완되는 스트레인을 계 측하였다. Schajer가 제안한 멱급수법과 최소장승법을 적용하여 균일응력장 또는 구 배 응력장에서 측정되는 스트레인을 잔류응력으로 환산하였으며, 환산된 잔류응력과 실제로 작용하는 응력을 비교하므로서 이론적으로 제시된 멱급수법과 최소자승법의 타 당성을 실험적으로 검토하는데 본 연구의 목적이 있다. 이 때 얕은 구멍깊이 (0.3∼ 1.2mm)에서 측정되는 스트레인을 이용하여 Schajer의 제안에 따라 잔류응력을 산정하 므로서, 잔류응력 계측 대상 구조물을 가급적 덜파괴시키며 잔류응력을 측정할 수 있 는지 여부를 실험적으로 검토하였다.

• 마이크로전자및패키징학회지
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• 제11권4호
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• pp.49-53
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• 2004

고분자 재료가 전자산업분야에서 절연재료나 접착제로 널리 사용되고 있다. 실리콘 기판위에 증착된 고분자 층에는 기판과의 열팽창계수 차이로 인해 열응력이 발생할 수 있다 고분자 층과 기판사이의 열적 성질의 차이로 인해 큰 잔류응력이 야기된다. 본 연구에서는 레이저 주사법을 이용하여 열적변형으로 인한 곡률변화를 측정한 후, 해석적 방법을 적용하여 수정된 박막 물성을 구하는 방법을 제시하고 있다.

• 한국표면공학회지
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• 제39권5호
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• pp.199-205
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• 2006

Titanium nitride (TiN) coatings were produced on AISI 420 stainless steel by DC magnetron sputtering of a Ti target changing the processing variables, such as the flow rate of $N_2/Ar$, substrate temperature and the existence of Ti interlayer between TiN coatings and substrates. The hardness and residual stress in the films were investigated using nanoindentation and a laser scanning device, respectively. The stoichiometry and surface morphology were investigated using X-Ray Diffraction and SEM. The corrosion property of the films was also studied using a polarization method in NaCl (0.9%) solution. Mechanical properties including hardness and residual stress were related to the ratio of $N_2/Ar$ flow rate. The corrosion resistance also was related to the processing variables.

• 한국표면공학회지
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• 제48권1호
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• pp.23-26
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• 2015

What causes the transformation of a solar cell is the behavior difference of thermal expansion occurred between the substrate and the layer of semiconductor used in the solar cell. Therefore, the substrate has to possess a behavior of thermal expansion that is similar with that of semiconductor layer. This study employed electroforming to manufacture Fe-Ni alloy materials of different compositions. To verify the result from a finite element analysis, a two-dimensional Mo substrate was calculated and its verification experiment was conducted. The absolute values from the finite element analysis of Mo/substrate structure and its verification experiment showed a difference. However, the size of residual stress of individual substrate compositions had a similar tendency. Two-dimensional CIGS/Mo/$SiO_2$/substrate was modeled. Looking into the residual stress of CIGS layer occurred while the temperature declined from $550^{\circ}C$ to room temperature, the smallest residual stress was found with the use of Fe-52 wt%Ni substrate material.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.94.2-94.2
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• 2010

Indium tin oxide (ITO) Thin films were grown on Non-alkarai glass Substrates by PVD method and Subsequently Subjected to ($100^{\circ}C-350^{\circ}C$) Thermal Annealing (TA) In Nitr Oxygen ambinent. Most of all, The effect of TA treatment on the structural properties were studied by using X-Ray diffraction and atomic force microscopy, while optical properties were studied by UV-Transmittance measurements. After TA treatment, the XRD spectra have shown an effective relaxation of the residual compressive stress, As a result, XRD peaks increase of the intensity and narrowing of full width at half-maximun (FWHM). In addtion The microstructure, The surface morphology, the optical transmittance changed and improved, and we investigated The effects of temperature, Time and atmosphere during the TA on the structural and electrical properties of the ITO/glass on TA at $300^{\circ}C$. As a results, the films are highly transparent (80%～89%) in visible region. AFM analysis shows that the films are very smooth with root mean square surface roughness 0.58nm -2.75nm thickness film. It is observed that resistivity of the films drcreases T0 $1.05{\times}10^{-4}{\Omega}cmt$ $6.06{\times}10^{-4}{\Omega}cm$, while mobility increases from $152cm^2/vs$ to $275cm^2/vs$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.43-43
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• 2011

BN(Boron Nitride)은 온도와 압력 조건에 따라 안정한 상이 sp3 결합인 cubic 구조의 BN(cBN)과 sp2 결합인 hexagonal 구조의 BN(hBN or tBN)으로 나뉘는데, 이 중 cBN은 우수한 기계적, 물리적, 화학적 특성으로 인해 박막 분야에서 매우 높은 응용가능성을 지니고 있다. 하지만 cBN 박막의 합성과정에서의 필수적인 요소인 높은 압축잔류응력은 cBN을 응용분야에 적용하는데 있어 한계점으로 계속 남아 있었다. 그동안 이러한 잔류응력을 감소시키기 위해 열처리, 이온 주입, 제 3의 물질 첨가 등 다양한 관점에서 접근한 연구들이 진행되어 왔다. 본 연구에서는 cBN 합성과정에서 잔류응력을 감소시키기 위한 방법으로 수소를 첨가하였고, 그에 따른 잔류응력의 변화를 분석하고, 그 과정에서 잔류응력의 형성에 수소가 어떤 역할을 하는지 규명하고자 하였다. cBN 박막은 hBN을 target으로한 unbalanced magnetron sputtering를 사용하여, 실리콘 wafer 위에 합성하였다. 증착압력은 1.3mTorr로, 수소의 첨가량을 증가시키며 잔류응력과 cBN fraction을 관찰하였다. cBN fraction은 FTIR로 분석하였고, 잔류응력은 실리콘 strip의 in-situ 곡률측정법으로 계산하였다. cBN 박막의 조성과 구조 분석, 수소의 역할 규명을 위해 RBS 및 HRTEM을 이용하였다.

• 한국진공학회지
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• 제18권3호
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• pp.213-220
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• 2009

Al이 도핑된 투명 전도성 Al:ZnO (AZO) 박막에 대한 RF magnetron sputtering 증착 법을 이용한 저온 최적공정조건을 연구하였다. 투명전극 재료로써의 AZO 박막의 전기적, 결정학적 물성을 최대한 향상시키기 위해서, in-situ상태에서 유리기판상에 최적화된 증착 조건의 AZO 버퍼 층을 삽입하는 이중박막 구조를 제작하였다. RF 인가 전력 $50{\sim}60\;W$에서 증착된 버퍼층 위에 120 W의 RF 전력에서 성장한 AZO 박막의 경우, 비저항 $3.9{\times}10^{-4}{\Omega}cm$, 전하 캐리어농도 $1.22{\times}10^{21}/cm^3$, 홀 이동도 $9.9\;cm^2/Vs$의 전기적 특성을 보였다. 이러한 결과는 버퍼 층이 없는 기존의 단일 구조와 비슷하나, 전기적 비저항 특성을 약 30% 정도 향상시킬 수 있었으며, 전기적 특성의 향상 원인을 $Ar^+$ 이온의 입사 에너지의 변화에 따른 버퍼 층의 압축응력과 결정화 정도와의 의존성으로 설명하였다.

• Bulletin of the Korean Chemical Society
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• 제28권4호
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• pp.533-537
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• 2007

This paper describes the heteroepitaxial growth of single-crystalline 3C-SiC (cubic silicon carbide) thin films on Si (100) wafers by atmospheric pressure chemical vapor deposition (APCVD) at 1350 oC for micro/nanoelectromechanical system (M/NEMS) applications, in which hexamethyldisilane (HMDS, Si2(CH3)6) was used as a safe organosilane single-source precursor. The HMDS flow rate was 0.5 sccm and the H2 carrier gas flow rate was 2.5 slm. The HMDS flow rate was important in obtaing a mirror-like crystalline surface. The growth rate of the 3C-SiC film in this work was 4.3 μm/h. A 3C-SiC epitaxial film grown on the Si (100) substrate was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Raman scattering, respectively. These results show that the main chemical components of the grown film were single-crystalline 3C-SiC layers. The 3C-SiC film had a very good crystal quality without twins, defects or dislocations, and a very low residual stress.

• Progress in Superconductivity
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• 제11권1호
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• pp.36-41
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• 2009

Superconducting quantum phenomena are getting attention from the field of metrology area. Following its first successful application of Josephson effect to voltage standard, piconewton force standard was suggested as a candidate for the next application of superconducting quantum effects in metrology. It is predicted that a micron-sized superconducting Nb ring in a strong magnetic field gradient generates a quantized force of the order of sub-piconewtons. In this work, we studied the design and fabrication of Nb superconducting quantum interference device (SQUID) on an ultra-thin silicon cantilever. The Nb SQUID and electrodes were structured on a silicon-on-insulator (SOI) wafer by dc magnetron sputtering and lift-off lithography. Using the resulting SOI wafer, we fabricated V-shaped and parallel-beam cantilevers, each with a $30-{\mu}m$-wide paddle; the length, width, and thickness of each cantilever arm were typically $440{\mu}m,\;4.5{\mu}m$, and $0.34{\mu}m$, respectively. However, the cantilevers underwent bending, a technical difficulty commonly encountered during the fabrication of electrical circuits on ultra-soft mechanical substrates. In order to circumvent this difficulty, we controlled the Ar pressure during Nb sputtering to minimize the intrinsic stress in the Nb film and studied the effect of residual stress on the resultant device.

• 한국재료학회지
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• 제22권1호
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• pp.8-15
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• 2012

Silicon-based thin film was prepared at room temperature by an electrochemical deposition method and a feasibility study was conducted for its use as an anode material in a rechargeable lithium battery. The growth of the electrodeposits was mainly concentrated on the surface defects of the Cu substrate while that growth was trivial on the defect-free surface region. Intentional formation of random defects on the substrate by chemical etching led to uniform formation of deposits throughout the surface. The morphology of the electrodeposits reflected first the roughened surface of the substrate, but it became flattened as the deposition time increased, due primarily to the concentration of reduction current on the convex region of the deposits. The electrodeposits proved to be amorphous and to contain chlorine and carbon, together with silicon, indicating that the electrolyte is captured in the deposits during the fabrication process. The silicon in the deposits readily reacted with lithium, but thick deposits resulted in significant reaction overvoltage. The charge efficiency of oxidation (lithiation) to reduction (delithiation) was higher in the relatively thick deposit. This abnormal behavior needs to clarified in view of the thickness dependence of the internal residual stress and the relaxation tendency of the reaction-induced stress due to the porous structure of the deposits and the deposit components other than silicon.