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구리 전기도금박막의 자기-어닐링 과정에 대한 동력학적 고찰
梁鐵雄,金忠彦 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.1
This paper concerns the kinetics of the self-annealing mechanism in electroplated Cu thin films. The annealing kinetics of electroplated Cu thin films is characterized by monitoring the change in the sheet resistance and X-ray diffraction intensity with the variation of film thickness and temperature. The kinetic parameters of annealing, the time exponent and the activation energy, are determined by fitting the results to the KJMA (Kolmogorov, Johnson, Mehl and Avrami) model. It is found that the film thickness has little influence on the activation energy but does change the time exponent. From subsequent analysis of the final grain structure using transmission electron microscopy, it is then concluded that the self-annealing occurs mainly by the process of the recrystallization and that annealing kinetics dependence on film thickness stems from the hindering of grain boundary migration at the Cu/substrate interface. In case the film thickness is smaller than the nuclei size or when there is not enough stored energy in the film to drive nucleation and grain growth, the self-annealing may occur by recovery.
분석전자현미경을 이용한 Invar 합금의 저온 상변화 연구
양철웅 成均館大學校 科學技術硏究所 1998 論文集 Vol.49 No.2
The low-temperature phase transformations occurring in the invar alloys can be understood by investigating microstructure and microchemistry of the meteoritic metal which is basically an Fe-Ni alloy. At the invar composition (Fe-36Ni), meteoritic metal contains a cloudy zone structure composed of an island region (high Ni ordered FeNi with low Ni precipitates) and a surrounding honeycomb region (low Ni single phase martensite). The low-temperature Fe-Ni phase diagram has been assessed experimentally by investigating Fe-Ni regions of meteorites using high resolution analytical electron microscopy techniques. The microstructural development of the cloudy zone can be understood by application of the Fe-Ni phase diagram. At low temperatures below 400℃, metastable phase transformations such as spinodal decomposition, ordering reaction, precipitation and martensitic transformation occur and form metastable phases in the parent γ -fcc phase.
Time-Resolved Observation of Carbon Nanotube Growth by Using an Environmental TEM
양철웅,박종윤,강한별,Jae-Wook Lee,Ji-Beom Yoo,Ji-Hwan Bae,Min-Ho Park 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.6
We report in-situ observations of the growth of carbon nanotubes (CNTs) by using an environmental transmission electron microscope (E-TEM). E-TEM is a specially designed transmission electron microscope (TEM) with a differential pumping system where gas can be flowed into the specimen whilst keeping a high vacuum level in the remainder of the TEM column. In order to grow CNTs, Ni nanoparticles as a catalyst were deposited on holey SiO$_x$-TEM mesh grids by using a solution phase catalyst deposition method. Chemical vapor deposition (CVD) was carried out inside the TEM column by flowing acetylene gas ($\sim$10 mTorr) over the Ni catalyst heated to 600 $^\circ$C. At a given growth condition, the CNTs grew with a serpentine morphology with the growing apex frequently returning to the substrate to become anchored at both ends. The growth durations were observed to be quite short, and the growth rate was estimated to be $\sim$0.2 mm/sec, which is relatively fast, at low C$_2$H$_2$ pressures of $<$10 mTorr. Growth was confirmed to occur at the tip where the nickel catalyst particle is located, rather than at the base of the tube, as suggested in the tip growth model. Both multi-walled CNT and single-walled CNT were synthesized simultaneously under the same reaction conditions. This suggests that the nature of the catalyst still plays an important role in determining the characteristics of the CNT even though these characteristics can be controlled by altering either the reaction temperature or pressure.
Modelling FCW 용착금속의 기계적 성질에 미치는 Si, Mn의 영향
양철웅,강춘식,김경중 대한용접접합학회 1990 대한용접·접합학회지 Vol.8 No.2
The effect of silicon and manganese, in the ranges of 0.3% to 1.0wt% Si and 0.7 to 2.6wt%Mn, on the microstructure and mechanical properties of flux cored arc welded deposits have been investigated for the purpose of improving mechanical properties. Microstructure of weld metals was mainly influenced by manganese content, and manganese increased the volum fraction of acicular ferrite and refined the microstructure. Also, tensile properties were governed by manganese content, ultimate tensile strength and yield strength were increased by approximately 82MPa and 58MPa per 1% Mn addition to the deposit. Toughness was improved by increasing Mn content and lowering Si content. Optimal impact properties were obtained at above 1.8wt% Mn and below 0.5wt% Si. Acicular ferrite was predominant factor in improving mechanical properties. Formation of acicular ferrite was promoted by manganese and no direct relationship between AF(acicular ferrite) proportion and oxygen in weld metal was found.
안병선,양철웅,권예나,오진수,신연주,주재선 한국현미경학회 2019 Applied microscopy Vol.49 No.2
Focused ion beam method, which has excellent capabilities such as local deposition and selective etching, is widely used for micro-electromechanical system (MEMS)-based in situ transmission electron microscopy (TEM) sample fabrication. Among the MEMS chips in which one can apply various external stimuli, the electrical MEMS chips require connection between the TEM sample and the electrodes in MEMS chip, and a connected deposition material with low electrical resistance is required to apply the electrical signal. Therefore, in this study, we introduce an optimized condition by comparing the electrical resistance for C-, Pt-, and W- ion beam induced deposition (IBID) at 30 kV and electron beam induced deposition (EBID) at 1 and 5 kV. The W-IBID at 30 kV with the lowest electrical resistance of about 30 Ω shows better electrical properties than C- and Pt-IBID electrodes. The W-EBID at 1 kV has lower electrical resistance than that at 5 kV; thus, confirming its potential as an electrode. Therefore, for the materials that are susceptible to ion beam damage, it is recommended to fabricate electrical connections using W-EBID at 1 kV.
A Study on Oxidation Behavior of Poly-Si1-xGex Films
강한별,양철웅,민병기,고대홍,J. H. Lee,강성관,안태항,여인석,K. C. Lee,T. W. Lee,Y. H. Lee 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
We have investigated the oxidation behavior of poly-Si$_{1-x}$Ge$_x$ films with 20 \%, 40 \%, and 60 \% Ge content in both dry and wet oxygen ambient. Poly-Si$_{1-x}$Ge$_x$ films with various compositions and about 1000 {\AA} in thickness were deposited on oxidized Si wafers (with 1000 {\AA} thick thermal SiO$_2$). Oxidation was carried out in a conventional tube furnace at 800 $^\circ$C. The composition and thickness of the oxide were analyzed by RBS using rump simulation. The redistribution and chemical bonding of Si, Ge, and O elements were analyzed by XPS. The microstructure and phases formed in the films were analyzed by HR-TEM. In this study, it was found that Si was oxidized preferentially when the content of Ge in the alloy was low (20 \%, 40 \%). SiO$_2$ was formed on the poly-Si$_{1-x}$Ge$_x$ films, rejecting Ge and the oxidation rate of the poly-Si$_{1-x}$Ge$_x$ films depends weakly on the Ge concentration. On the other hand, Si and Ge were oxidized simultaneously when the content of Ge was high (60 \%). The formation of a mixed oxide layer on the poly-Si$_{1-x}$Ge$_x$ films was observed. It was also found that oxide surface has a tendency to be flat from the initial oxidation stage due to the fast oxidation rate of Ge-rich films.