• 대한금속재료학회지
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• 제48권2호
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• pp.175-179
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• 2010

We investigated the thermal conductivity of individual single-crystalline PbTe nanowires grown by chemical vapor transport method. Suspended MEMS was utilized to precisely measure the thermal conductivity of an individual nanowire. The thermal conductivity of a PbTe nanowire with diameter of 292 nm was measured to be $1.8W/m{\cdot}K$ at 300 K, which is about two thirds of that of bulk PbTe. This result indicates that the thermal conduction through a PbTe nanowire is effectively suppressed by the enhanced phonon boundary scattering. As the diameter of a PbTe nanowire decreases, the corresponding thermal conductivity linearly decreases.

• 한국압력기기공학회 논문집
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• 제17권2호
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• pp.109-118
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• 2021

In the periodic surveillance material test for the spacer component of fuel channel assembly in CANDU, a microstructural characterization analysis is required in addition to the mechanical property evaluation test. In this study, detailed microstructure analysis and simple mechanical property evaluation of archive spacer parts were conducted to indirectly support the surveillance test and assist in the study of spacer material degradation. We investigated the microstructural characteristics of the spacer garter spring coil through comparative analysis with the plate material. The main microstructure characteristics of the garter spring coil X-750 are represented by the fine grain size distribution, the ordering phase distribution developed inside the matrix, the high dislocation density inside the grains, and the arrangement of coarse carbides. In addition, the yield strength of the garter spring coil X-750 was indirectly evaluated to be approximately 1 GPa. We also established an analytical method to elucidate the microstructural evolution of the radioactive spacer garter spring coil X-750 based on Canadian research experiences. Finally, we confirmed the measurement technique for helium bubble formation through TEM examination on the helium implanted X-750 material.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.2742-2746
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• 2023

The corrosion behavior of copper immersed in dilute oxychloride solution (100 mM) was studied through surface investigation and in-situ monitoring of open-circuit potential. The copper corrosion was initiated with copper dissolution into a form of CuCl^-₂, resulting in mass decrease within the first 40 h of immersion. This was followed by a hydrolysis reaction initiated by the CuCl^-₂ at the copper surface, after which oxide products were formed and deposited on the surface, resulting in a mass increase. The formation of nucleation sites for copper oxide and its lateral extension during the corrosion process were examined using focused ion beam (FIB)-scanning electron microscopy (SEM). The presence of metastable compounds such as atacamite (CuCl₂·3Cu(OH)₂) on the corroded copper surface was revealed by X-ray photoelectron spectra (XPS) and transmission electron microscopy (TEM)-energy dispersive spectrometry (EDS) analysis.

• 대한기계학회논문집A
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• 제31권5호
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• pp.550-555
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• 2007

The effective fracture toughness testing of materials intended for application in Micro Electro Mechanical Systems (MEMS) devices is required in order to improve understanding of how micro sized material used in device may be expected to perform upon the micro scale. ${\gamma}$-TiAl based materials are being considered for application in MEMS devices at elevated temperatures. Especially, in Alloy 4, both ${\alpha}_2$ and ${\gamma}$ lamellae were altered markedly in 3,000 h, $700^{\circ}C$ exposure. Parallel decomposition of coarse ${\alpha}_2$ into bunches of very fine (${\alpha}_2+{\gamma}$) lamellae. Parallel decomposition of coarse ${\alpha}_2$ into bunches of very fine (${\alpha}_2+{\gamma}$) lamellae. The materials were examined 2 types Alloy 4 on heat exposed specimen($700^{\circ}C$, 3,000 h) and no heat exposed one. Micro sized cantilever beams were prepared mechanical polishing on both side at $25{\sim}30{\mu}m$ and electro final stage polishing to observe lamellar orientation of same colony with EBSD (Electron Backscatter Diffraction Pattern). Through lamellar orientation as inter-lamellae or trans-lamellae, Cantilever beam was fabricated with Focused Ion Beam(FIB). The directional behavior of the lamellar structure was important property in single material, because of the effects of the different processing method and variations in properties according to lamellar orientation. In MEMS application, it is first necessary to have a reliable understanding of the manufacturing methods to be used to produce micro structure.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 춘계학술대회 논문집 디스플레이 광소자 분야
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• pp.135-138
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• 2005

현재 널리 상용되어 있는PDP는 3전극 변방전형이다. 3전극 면장전형 PDP는 주방전이 유전체 아래에 서로 평행하게 위치하고 있는 ITO투명전극 사이에서 발생한다. 따라서 방전시의 전기장은 MgO 보호막 위에서 아치형태로 형성되게 된다. 플라스마 방전 시 전자에 의해 이온화된 이온 입자들은 전기장에 의해 그 방전경로가 정해지게 된다. 물론 전기장은 표면에서 수직이지만 전기장에 의해 가속되어진 이온입자들은 MgO 보호막에 기울어져서 입사하게 된다. 따라서 플라스마 방전시의 이온들의 MgO 보호막으로의 입사각은 매우 다양하다. $\gamma$-FIB (Focused ion beam) 시스템은 이온입사에 의한 물질의 이차전자방출계수 측정에 효과적인 장비이다. 본 실험은 이러한 $\gamma$-FIB 시스템을 이용하여 다양한 각도로 입사하는 이온빔에 의한 MgO 보호막의 이차전자방출계수를 측정하였다. 또한 이온화 에너지가 다른 여러 종류의 불활성 기체를 사용하여 이온의 입사하는 각도에 따른 MgO 보호막의 일함수를 측정하였다. 이온빔의 입사각은 각각 $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$로 변화시키면서 이차전자방출계수 및 일함수를 측정하였다. 이러한 실험을 통해 입사각이 클수록 이차전자방출계수는 증가하고 일수는 감소하는 것을 확인 할 수 있었다.

• Radiation Oncology Journal
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• 제18권2호
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• pp.150-156
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• 2000

서론 :정위방사선치료는 높은 정밀도로 크기가 작고 구형인 병변에 국한하여 방사선을 조사할 수 있는 기술이지만 병변의 모양이 구형이 아닌 경우에는 병변 주변의 정상조직에 고선량의 방사선이 조사될 수 있다. 본 연구는 독립턱을 부분적으로 폐쇄하여 방사선량 분포를 개선하는 방법, 선량계산과 선량분포의 도시방법을 보고하고자 한다. 방법 :정위방사선치료 시의 호의 궤적상 병변은 방사선조사영역 내에 포함하면서 주변 정상조직을 최대한 차폐하도록 원형 콜리메이터와 독립턱 부분페쇄를 적절히 조합하였다. 물 펜톰과 마이크로 전리함을 이용하여 출력인자와 조직최대선량비를 측정하여 이론적 계산치와 비교하였다. 필름선량측정계를 이용하여 5 cm 깊이에서의 심부선량분포를 측정하여 계산치와 비교하였다. 이와 같은 측정자료를 자가 개발한 치료계획 프로그램에 반영하여 뇌전이 환자의 정위 방사선치료 선량계산과 도시에 적용하여 원형 콜리메이터만을 이용하였을 경우와 독립턱 부분폐쇄를 추가하였을 경우의 병변과 정상 뇌의 선량체적표를 각각 비교하였다. 결과 : 5.0 cm 직경의 원형 콜리메이터를 사용하고 한 쪽 독립턱을 중심축으로부터 30 mm, 15.5 mm, 8.6 mm, 0 mm 까지 열었을 때 측정한 출력인자와 조직최대선량비는 계산치와 각각 0.5%와 0.3%의 오차범위로 잘 부합하였다. 필름선량계로 얻은 5 cm 깊이의 심부선량분포도 역시 계산치와 잘 부합하였다. 자가 개발한 치료계획 프로그램으로 병변과 정상 뇌의 선량체적표를의 상호 비교를 통하여 독립턱 부분폐쇄를 적용한 경우에 있어서 보다 개선된 선량분포를 얻을 수 있음을 확인하였다. 결론 : 정위방사선치료에 있어서 독립턱의 부분폐쇄를 적용함으로써 보다 개선된 선량분포계획을 얻을 수 있으며 이를 적용하여 비교적 크기가 크고 모양이 불규칙한 병변에 대하여도 정위방사선치료를 확대 적용할 수 있겠다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.358-358
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• 2012

The application of BZO (Boron-doped Zinc Oxide) films use as the TCO(Transparent Conductive Oxide) material for display and solar cell industries, where the conductivity of the BZO films plays a critical role for improvement of cell performance. Thin BZO films are deposited on glass substrates by using RF sputter system. Then charging flow rates of O2 gas from zero to 10 sccm, thereby controlling the impurity concentration of BZO. BZO deposited on soda lime glass and RF power was 300 W, frequency was 13.56 MHz, and working pressure was $5.0{\times}10-6$ Torr. The Substrate and glass between distance 200 mm. We measured resistivity, conductivity, mobility by hall measurement system. Optical properties measured by photo voltaic device analysis system. We measured surface build according to oxygen flow rate from XPS (X-ray Photoelectron Spectroscopy) system. The profile of the energy distribution of the electrons emitted from BZO films by the Auger neutralization is measured and rescaled so that Auger self-convolution arises, revealing the detail structure of the valence band. It may be observed coefficient ${\gamma}$ of the secondary electron emission from BZO by using ${\gamma}$-FIB (Gamma-Focused Ion Beam) system. We observed the change in electrical conductivity by correlation of the valence band structure. Therefore one of the key issues in BZO films may be the valence band that detail structure dominates performance of solar cell devices. Demonstrating the secondary electron emission by the Auger neutralization of ions is useful for the determination of the characteristics of BZO films for solar cell and display developments.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 및 기술 세미나 논문집 디스플레이 광소자
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• pp.42-42
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• 2008

Considerable attention has been focused on the applications of flexible liquid crystal (LC)-based displays because of their many potential advantages, such as portability, durability, light weight, thin packaging, flexibility, and low power consumption. To develop flexible LCDs that are capable of delivering high-quality moving images, like conventional glass-substrate LCDs, the LC device structure must have a stable alignment layer of LC molecules, concurrently support uniform cell gaps, and tightly bind two flexible substrates under external tension. However, stable LC molecular alignment has not been achieved because of the layerless LC alignment, and consequently high-quality images cannot be guaranteed. To solve these critical problems, we have proposed a PDMS pixel-wall based bonding method via the IB irradiation was developed for fasten the two substrates together strongly and maintain uniform cell gaps. The effect of the IB irradiation on PDMS with PI surface was also evaluated by side structure configuration and a result of x-ray photoelectron spectroscopic analysis of PDMS interlayer as a function of binder with substrates. large number of PDMS pixel-walls are tightly fastened to the surface of each flexible substrate and could maintain a constant cell gap between the LC molecules without using any other epoxy or polymer. To enhance the electro-optical performance of the LC device, we applied an alignment method that creates pretilt angle on the PI surface via ion beam irradiation. Using this approach, our flexible LCDs have a contrast ratio of 132:1 and a response time of about 15 ms, resulting in highly reliable electro-optical performance in the bent state, comparable to that of glass-substrate LCDs.

• 한국전기전자재료학회논문지
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• 제23권6호
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• pp.481-486
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• 2010

ENIG (electroless Ni immersion gold) is one of surface finishing which has been most widely used in fine pitch SMT (surface mount technology) and BGA (ball grid array) packaging process. The reliability for package bondability is mainly affected by interfacial reaction between solder and surface finishing. Since the behavior of IMC (intermetallic compound), or the interfacial reaction between Ni and solder, affects to some product reliabilities such as solderability and bondability, understanding behavior of IMC should be important issue. Thus, we studied the properties of ENIG with P contents (9 wt% and 13 wt%), where the P contents is one of main factors in formation of IMC layer. The effect of P content was discussed using the results obtained from FE-SEM(field-emission scanning electron microscope), EPMA(electron probe micro analyzer), EDS(energy dispersive spectroscopy) and Dual-FIB(focused ion beam). Especially, we observed needle type irregular IMC layer with decreasing Ni contents under high P contents (13 wt%). Also, we found how IMC layer affects to bondability with forming continuous Kirkendall voids and thick P-rich layer.

• 한국재료학회지
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• 제26권9호
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• pp.486-492
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• 2016

Tungsten (W) thin film was deposited at $400^{\circ}C$ using pulsed chemical vapor deposition (pulsed CVD); film was then evaluated as a nucleation layer for W-plug deposition at the contact, with an ultrahigh aspect ratio of about 14~15 (top opening diameter: 240~250 nm, bottom diameter: 98~100 nm) for dynamic random access memory. The deposition stage of pulsed CVD has four steps resulting in one deposition cycle: (1) Reaction of $WF_6$ with $SiH_4$. (2) Inert gas purge. (3) $SiH_4$ exposure without $WF_6$ supply. (4) Inert gas purge while conventional CVD consists of the continuous reaction of $WF_6$ and $SiH_4$. The pulsed CVD-W film showed better conformality at contacts compared to that of conventional CVD-W nucleation layer. It was found that resistivities of films deposited by pulsed CVD were closely related with the phases formed and with the microstructure, as characterized by the grain size. A lower contact resistance was obtained by using pulsed CVD-W film as a nucleation layer compared to that of the conventional CVD-W nucleation layer, even though the former has a higher resistivity (${\sim}100{\mu}{\Omega}-cm$) than that of the latter (${\sim}25{\mu}{\Omega}-cm$). The plan-view scanning electron microscopy images after focused ion beam milling showed that the lower contact resistance of the pulsed CVD-W based W-plug fill scheme was mainly due to its better plug filling capability.