• Applied Microscopy
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• 제48권4호
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• pp.128-129
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• 2018

Soft ferromagnetic materials are utilized for various electromagnetic devices such as magnetic recording heads and magnetic shielding. In situ observation of magnetic microstructures and domain wall motions are prerequisite for understanding and improving their magnetic properties. In this work, by the Fresnel (out-of-focus) method of Lorentz microscopy, we observe the domain wall motions of polycrystalline Ni/Ti thin film layers triggered by single-shot laser pulse. Random motions of domain walls were visualized at every single pulse.

• 한국진공학회지
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• 제8권3B호
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• pp.283-289
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• 1999

Multilayer thin film reference materials for the sputter depth profiling analysis are used to calibrate the sputter depth scale by measuring the sputtering rate and to optimize the sputtering conditions for the best depth resolution. Surface analysis group of Korea Research Institute of Standards and science (KRISS) have developed various types of multilayer thin films by using an ion beam sputter deposition and in-situ surface analysis system. The chemical states of the thin films reference materials were certified by in-situ XPS and the thicknesses were certified by transmission electron microscopy (TEM).

• 한국가시화정보학회지
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• 제2권1호
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• pp.12-17
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• 2004

The physical characteristics of soot near the soot inception point were investigated with various measurements. In-situ measurements of particle size and volume fraction were introduced based on time resolved laser-induced incandescence (TIRE-LII) and laser-induced ion mobility (LIIM). The one has more convenience and accuracy than conventional LII technique and the other works best for particle sizes of a few nanometers at high concentrations in a uniform concentration field. A complementary ex-situ measurement of particle size is nano differential mobility analyzer (Nano-DMA), which recently developed for measuring particle sizes between 2nm and 100nm and provides high-resolution size information for early soot. Particles will be also collected on transmission electron microscope (TEM) grids using rapid thermophoretic sampling and analyzed for morphology. These measurements will allow fresh and original insight into the characterizing soot inception process. The measured physical properties of incipient soot will clarify the controlling growth mechanism combined with chemical ones, and the dominant mechanism for soot modeling can be deduced from the information.

• 한국재료학회지
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• 제21권3호
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• pp.174-179
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• 2011

Ultra-thin aluminum (Al) and tin (Sn) films were grown by dc magnetron sputtering on a glass substrate. The electrical resistance R of films was measured in-situ method during the film growth. Also transmission electron microscopy (TEM) study was carried out to observe the microstructure of the films. In the ultra-thin film study, an exact determination of a coalescence thickness and a continuous film thickness is very important. Therefore, we tried to measure the minimum thickness for continuous film (dmin) by means of a graphical method using a number of different y-values as a function of film thickness. The raw date obtained in this study provides a graph of in-situ resistance of metal film as a function of film thickness. For the Al film, there occurs a maximum value in a graph of in-situ electrical resistance versus film thickness. Using the results in this study, we could define clearly the minimum thickness for continuous film where the position of minimum values in the graph when we put the value of Rd3 to y-axis and the film thickness to x-axis. The measured values for the minimum thickness for continuous film are 21 nm and 16 nm for sputtered Al and Sn films, respectively. The new method for defining the minimum thickness for continuous film in this study can be utilized in a basic data when we design an ultra-thin film for the metallization application in nano-scale devices.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.46.1-46.1
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• 2009

산업이 점차 발달함에 따라 발생하는 환경오염으로 인해 인간의 삶에 있어 불가분의 관계에 있는 물에 대한 관심이 지속적으로 높아지고 있는 추세이다. 각종 질병의 요인이 되는 박테리아는 주로 물을 운송 매개체로 하기 때문에 이로 인한 물의 오염으로 인도의 경우 모든 질병 발생의 80%를 차지하는 것으로 세계보건기구(WHO)에 의해 보고되었다. 현재까지물 또는 공기의 항균 및 살균 정화를 위해 화학적, 생물학적 방식 등 다양한 기술이 개발되었으나 박테리아와같은 세균제거에는 무리가 있는 실정이다. 따라서 본 연구에서는 여러 물질 중에서도 특히 항균작용(Antibacterial activity)이 탁월한 은(Ag)을 나노입자화하여 in-situ 코팅을 통한 다공성 알루미늄 하이드록사이드 나노복합재의 제조함으로써 생물학, 생체의용공학, 약학 등에 응용될 수 있는 새로운 형태의 항균재료제조방법을 제안하였다. 우선, 다공성 알루미늄 하이드록사이드기판은 알루미늄 기판에 알칼리 표면개질을 실시함으로서 표면에 마이크로포어가 형성된 알루미늄 하이드록사이드 기판을 제조하였다. 이렇게 제조된 다공성 기판에 Polyol 공정으로 은나노입자를 합성 및 분산시킴으로서 in-situ로 은나노입자가 분산된 알루미늄 하이드록사이드 나노복합재 기판을 만들수 있었다. 본 연구를 통하여 제조된 은나노입자가 분산된 알루미늄 하이드록사이드 나노복합재 기판은 주사전자현미경(SEM) 및 투과전자현미경(TEM)을 통하여 미세구조와 상분석을 실시하였으며 X선 광전자분석(XPS)를 이용하여 기판 표면의 화학적 상태를 분석하였다.

• 마이크로전자및패키징학회지
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• 제10권2호
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• pp.39-47
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• 2003

감광성 폴리이미드 위에 Cr을 RF 바이어스 스퍼터링 및 RF클리닝 후 DC 스퍼터링한 Cr/폴리이미드의 계면을 TEM으로 관찰하였다. RF power 밀도를 $0.13W/cm^2$에서 $2.12W/cm^2$로 증가시키면서 RF클리닝을 실시한 결과 폴리이미드의 에칭 양상이 둥근 모양에서 뾰족한 모양으로 변하였고 이방성 에칭으로 인해 거칠기가 크게 증가하였다. RF 바이어스 스퍼터링의 경우 RF power를 올리는 동안 RF 클리닝에 의해 폴리이미드가 에칭되었고, 에칭된 부분에 Cr이 증착된 계면을 단면으로 관찰한 결과 Cr과 폴리이미드가 겹쳐져서 혼합된 것처럼 보였다. 그러나 RF power를 올리는 시간을 단축시켜 Cr을 바이어스 스퍼터링했을 때에는 계면이 분명하게 관찰되어 Cr의 implantation이 일어나지 않았음을 알 수 있었다. RF 클리닝한 Cu/Cr/Polyimide를 필 테스트한 결과 짧은 시간의 RF 클리닝으로도 접착력이 크게 증가하였다. 그러므로 RF power를 올리는 동안 실시되었던 RF 클리닝이 RF 바이어스 스퍼터링한 Cr/Polyimide의 접착력 향상에 영향을 주었을 것으로 예상된다.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2394-2401
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• 2020

Octadecylamine is an effective film-forming amine that protects carbon steel from corrosion. In the present study, the effect of octadecylamine concentration on adsorption on a carbon steel surface was investigated in anaerobic alkaline solution by using SEM/EDS, TEM and the Materials Studio simulation techniques. TEM morphology observation and EDS elemental detection determine the thicknesses of octadecylamine film on a carbon steel surface, which are confirmed by the in-situ electrochemical impedance spectroscopy measurement and resistance calculation. The Materials Studio simulation reveals the number of octadecylamine film layers at different concentrations. Results obtained in this study indicate that adsorption of octadecylamine film on carbon steel proceeds with the multi-layer adsorption mechanism.

• 한국재료학회지
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• 제8권10호
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• pp.912-917
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• 1998

화학적 산화막(SiOx)이 형성된 Si(100)기판 위에 Co-silicide의 형성과 계면 형상에 관한 연구를 하였다. 화학적 산화막은 과산화수소수(H2O2)의 인위적 처리에 의해 약 2nm을 형성시켰다. 그 위에 5nm 두께의 Co 박막을 전자빔 증착기에 의해 증착시킨 후 열처리하여 Co-silicide를 형성하였다. 화학적 산화막 위에서 Co-silicide 반응기구를 알아 보기 위해 $500^{\circ}C$-$900^{\circ}C$의 온도 범위에서 ex-situ와 in-situ 열처리를 하였다. 이와같이 형성된 Co-silicide 시편의 상형성, 표면 및 계면 형상, 그리고 화학적 조성을 XRD, SEM, TEM, 그리고 AES를 이용하여 분석하였다. 분석 결과 es-situ 열처리시 $700^{\circ}C$까지 CoSi2 상은 형성되지 않았고 Co의 응집화현상이 일어났다. $800^{\circ}C$ 열처리한 경우에는 CoSI2가 형성되었고 facet 현상이 크게 나타났으며 불연속적인 grain 들이 형성되었다. In-situ 열처리한 경우에는 저온에서 ($550 ^{\circ}C$)반응하여 Co-silicide가 형성되기 시작하였으며 $600^{\circ}C$부터는 facet에 의해 박막의 특성이 나빠지기 시작했다. $550^{\circ}C$에서 Co가 화학적 산화막 층을 통해 확산하여 균질한 Co-silicide를 형성하였다. 이와같이 형성된 균질한 실리사이드 층을 이용하여 다단계(55$0^{\circ}C$-$650^{\circ}C$-$800^{\circ}C$)열처리에 의해 균질한 다결정 CoSI2의 형성이 관찰되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.99-99
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• 2013

In this talk, I will present two research works in progress, which are: i) mapping of piezoelectric polarization and associated charge density distribution in the heteroepitaxial InGaN/GaN multi-quantum well (MQW) structure of a light emitting diode (LED) by using inline electron holography and ii) in-situ observation of the polarization switching process of an ferroelectric Pb(Zr1-x,Tix)O3 (PZT) thin film capacitor under an applied electric field in transmission electron microscope (TEM). In the first part, I will show that strain as well as total charge density distributions can be mapped quantitatively across all the functional layers constituting a LED, including n-type GaN, InGaN/GaN MQWs, and p-type GaN with sub-nm spatial resolution (~0.8 nm) by using inline electron holography. The experimentally obtained strain maps were verified by comparison with finite element method simulations and confirmed that not only InGaN QWs (2.5 nm in thickness) but also GaN QBs (10 nm in thickness) in the MQW structure are strained complementary to accommodate the lattice misfit strain. Because of this complementary strain of GaN QBs, the strain gradient and also (piezoelectric) polarization gradient across the MQW changes more steeply than expected, resulting in more polarization charge density at the MQW interfaces than the typically expected value from the spontaneous polarization mismatch alone. By quantitative and comparative analysis of the total charge density map with the polarization charge map, we can clarify what extent of the polarization charges are compensated by the electrons supplied from the n-doped GaN QBs. Comparison with the simulated energy band diagrams with various screening parameters show that only 60% of the net polarization charges are compensated by the electrons from the GaN QBs, which results in the internal field of ~2.0 MV cm-1 across each pair of GaN/InGaN of the MQW structure. In the second part of my talk, I will present in-situ observations of the polarization switching process of a planar Ni/PZT/SrRuO3 capacitor using TEM. We observed the preferential, but asymmetric, nucleation and forward growth of switched c-domains at the PZT/electrode interfaces arising from the built-in electric field beneath each interface. The subsequent sideways growth was inhibited by the depolarization field due to the imperfect charge compensation at the counter electrode and preexisting a-domain walls, leading to asymmetric switching. It was found that the preexisting a-domains split into fine a- and c-domains constituting a $90^{\circ}$ stripe domain pattern during the $180^{\circ}$ polarization switching process, revealing that these domains also actively participated in the out-of-plane polarization switching. The real-time observations uncovered the origin of the switching asymmetry and further clarified the importance of charged domain walls and the interfaces with electrodes in the ferroelectric switching processes.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.385-385
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• 2012

Understanding the thermodynamics and structural transformation during the Metal-Insulator Transition (MIT) is critical to better understand the underlying physical origin of phase transition in the vanadiumdioxide ($VO_2$). Here, through the temperature-dependent in-situ high resolutiontransmission electron microscopy (HR-TEM), and systematic electrical transport study, we have shown that the tunable MIT transition of $VO_2$ nanowires is strongly affected by interplay between strain and domain nucleation by ion beam irradiation. Surprsingly, we have also observed that the $VO_2$ rutile (R) metallic phase could form directly in a strain-induced metastable monoclinic (M2) phase. These insights open the door toward more systematic approaches to synthesis for $VO_2$ nanostructures in desired phase and to use for applications including ultrafast optical switching, smart window, metamaterial, resistance RAM and synapse devices.