• Journal of Welding and Joining
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• 제17권4호
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• pp.32-38
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• 1999

PAL(Pohang Accelerator Laboratory) designed and manufactured a 5m-long straight vacuum chamber to adopt U7 undulator that is the first insertion device. Top and bottom plates of the vacuum chamber were made of Al alloy A5083-H321, and welded together by the GTAW welding. The leak rate is less than 1×{TEX}$10^{-10}${/TEX} torr·ℓ/s with negligible welding deformation. The pressure has been maintained below {TEX}$10^{-10}${/TEX} torr after installation. This paper reports the welding process and the method applied to achieve ultimate vacuum performance and t satisfy integrity of welds.

• Journal of Welding and Joining
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• 제13권1호
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• pp.73-77
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• 1995

이 글에서는 챔버의 용접에 대해서 기술하였다. 전자빔용접에 의하여 누설률이 1*$10^{-10}$ torr.1/sec 이하로 목표값을 만족하기 때문에 초고진공에 적합한 용접법이다. 챔버는 용접부에 trench 구조를 가져야 진공용접을 하는데 보다 효과적이다. 이것은 지금까지 전자빔 용접에서 시험되지 않은 것이기 때문에 향후 보다 많은 연구가 있으리라고 본다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.173.2-173.2
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• 2014

Thin nitride thin films were synthesized by reactive radio-frequency magnetron sputtering in the ultra high vacuum (UHV) chamber. To control the characteristics of thin films, tin nitride thin films were obtained various argon and nitrogen gas mixtures, especially low nitrogen gas ratios. Tin nitride thin films were analyzed with alpha step, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and 4 point probe measurement. The result of alpha step and SEM showed that the thickness of thin nitride thin films were decreased with increasing nitrogen gas ratios. The metallic tin structure was decreased and the amorphous tin nitride structure were observed by XRD with higher nitrogen gas ratios. The oxidation state of tin and nitride were studied with high resolution Sn 3d and N 1s XP spectra.

• 한국재료학회지
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• 제30권2호
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• pp.57-60
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• 2020

Titanium aluminides have attracted special interest as light-weight/high-temperature materials for structural applications. The major problem limiting practical use of these compounds is their poor ductility and formability. The powder metallurgy processing route has been an attractive alternative for such materials. A mixture of Ti and Al elemental powders was fabricated to a mechanical alloying process. The processed powder was hot pressed in a vacuum, and a fully densified compact with ultra-fine grain structure consisting of Ti₃Al intermetallic compound was obtained. During the compressive deformation of the compact at 1173 K, typical dynamic recrystallization (DR), which introduces a certain extent of grain refinement, was observed. The compact had high density and consisted of an ultra-fine equiaxial grain structure. Average grain diameter was 1.5 ㎛. Typical TEM micrographs depicting the internal structure of the specimen deformed to 0.09 true strain are provided, in which it can be seen that many small recrystallized grains having no apparent dislocation structure are generated at grain boundaries where well-developed dislocations with high density are observed in the neighboring grains. The compact showed a large m-value such as 0.44 at 1173 K. Moreover, the grain structure remained equiaxed during deformation at this temperature. Therefore, the compressive deformation of the compact was presumed to progress by superplastic flow, primarily controlled by DR.

• 폴리머
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• 제34권5호
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• pp.454-458
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• 2010

본 연구에서는 인공관절 베어링 부품으로 가장 널리 사용되는 초고분자량 폴리에틸렌(UHMWPE)을 대상으로 6가지 감마선 조사 방법에 따른 UHMWPE의 미세구조 변화를 비교 분석하였다. 감마선을 조사하지 않은 폴리에틸렌(UGI)과 비교하여, 기존의 멸균처리에 해당하는 공기 중 상온에서 감마선 조사한 폴리에틸렌(AR)의 결정화도와 가교 정도는 유의한 차이를 보이며 증가하였다. 감마선 조사 환경 중, 상온에서의 산소(AR)와 진공상태(VR) 영향을 비교하면, AR과 VR의 결정화도는 유의한 차이가 없었으며, VR의 가교정도는 유의한 차이를 보이며 증가하였다. 감마선 조사 환경 중, 진공상태에서의 상온(VR)과 극저온(V77) 영향을 비교하면, 결정화도와 가교정도 모두 유의한 차이가 없었다. 그러나, VR과 V77에서의 가교정도는 AR에서의 가교정도보다 유의한 차이를 보이며 증가하였다. 3가지 감마선 조사 환경에 대하여 감마선 조사 이후 열처리(/S) 영향을 비교하면, 결정화도는 AR/S와 VR/S에서 유의한 차이가 없었으나, V77/S에서는 유의한 차이를 보이며 감소하였다. 또한, 가교정도는 AR/S와 V77/S에서 유의한 차이를 보이며 증가하였으며, VR/S에서는 유의한 차이가 없었다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.530-537
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• 2004

Development of a versatile nanomanipulation tool is an overarching theme in nanotechnology. Such a tool will likely revolutionize the field given that it will enable fabrication and operation of a wealth of interesting nanodevices. This study seeks funding to create a novel nanomanipulation system with the ultimate goal of using this system for nanomanufacturing at the molecular level. The proposed design differs from existing approaches. It is based on a nanoscale ion trap integrated to a scanning prove microscope (SPM) tip. In this design, molecules to be assembled will be ionized and collected in the nanoscale ion trap all in an ultra high vacuum (UHV) environment. Once filled with the molecular ions, the nanoscale ion trap-SPM tip will be moved on a substrate surface using scanning probe microscopy techniques. The molecular ions will be placed at their precise locations on the surface. By virtue of the SPM, the devices that are being nanomanufactured will be imaged in real time as the molecular assembly process is carried out. In the later stages, automation of arrays of these nanomanipulators will be developed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.255-256
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• 2006

The electrical properties of viologen ($VC_8SH$) were studied in terms of the tunneling current characteristics using self-assembling techniques and ultra high vacuum scanning tunneling microscopy (UHV-STM). We fabricated the Au substrate were deposited by thermal evaporation system($420^{\circ}C$). Self-assembled monolayers (SAMs) were prepared on Au(111), which had been thermally deposited onto freshly cleaved, heated mica. The Au substrate was exposed to a 1 mM/L solution of Octanethiol in ethanol for 24 h to form a monolayer. After through rinsing the sample, it was exposed to a 0.1 mM/L solution of $VC_8SH$ in ethanol for 30 min. We measurement of the morphology on the single viologen molecule. The current-voltage (I-V) properties were measured at arbitary configured points on the surface of the sample by using a STS.

• 대한전자공학회논문지SD
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• 제39권9호
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• pp.1-10
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• 2002

유기 발광 다이오드를 위한 indium oxide (ITO) 기판을 여러 가지로 방법으로 표면처리를 하고, 이에 따른 atomic force microscopy (AFM)에 의한 morphology의 변화와 표면에서 변화된 원소들의 조성비를 Auger electron spectroscopy (AES)분석에 의하여 조사하였다. 또한 이 기판을 사용하여 초고진공분자선 증착방법에 의하여 유기 발광다이오드를 제작하고 그 특성을 조사하였다. 그 결과 산소플라즈마으로 표면 처리한 ITO 기판 위에 제조된 organic light-emitting diode (OLED)소자의 특성이 향상되었다. 그것은 AES의 분석에 의하면 ITO 표면의 오염된 탄소가 제거되고 ITO의 일함수가 증가되어 정공이 유기물 층으로 용이하게 주입한 결과로 판단된다.

• Applied Science and Convergence Technology
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• 제24권6호
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• pp.228-231
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• 2015

We investigated the adsorption structures and the initial growth mode of ultra-thin Al films on a W(110) surface at a high temperature. When Al atoms were adsorbed on the W(110) at the substrate temperature of 1100 K and with coverage of 0.5ML, Al atoms formed a p($2{\times}1$) double-domain structure. When the coverage was 1.0 ML, the double domain of a hexagonal structure (fcc(111) face) rotated ${\pm}5^{\circ}$ from the [100] direction of the W(110) surface and another distorted hexagonal structure were found. Low-energy electron diffraction results along with ion scattering spectroscopy results showed that the Al atoms followed the Volmer-Weber growth mode at a high temperature.

• Journal of Korean Vacuum Science & Technology
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• 제2권2호
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• pp.107-117
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• 1998

Epitaxial undoped and Sb-doped si films have been grown on Si(001) substrates at temperatures T between 80 and 750$^{\circ}C$ using energetic Si in ultra-high-vacuum Kr+-ion-beam sputter deposition(IBSD). Critical epitaxial thicknesses te, The average thickness of epitaxial layers, in undoped films were found to range from 8nm at Ts=80$^{\circ}C$ to > 1.2 ${\mu}$m at Ts=300$^{\circ}C$ while Sb incorporation probabilities $\sigma$sb varied from unity at Ts 550$^{\circ}C$ to 0.1 at 750$^{\circ}C$. These te and $\sigma$Sb values are approximately one and one-to-three orders of magnitude, respectively, higher than reported results achieved with molecular-beam epitaxy. Plan-view and cross-sectional transmission electron microscopy, high-resolution x-ray diffraction, channeling and axial angular-yield profiles by Rutherford back scattering spectroscopy for epitaxial Si1-x Gex(001) alloy films (0.15$\leq$x$\leq$0.30) demonstrated that the films are of extremely high crystalline quality. critical layer thicknesses hc the film thickness where strain relaxation starts, I these alloys wre found to increase rapidly with decreasing growth temperature. For Si0.70 Ge0.30, hc ranged from 35nm at Ts=550$^{\circ}C$ to 650nm at 350$^{\circ}C$ compared to an equilibrium value of 8nm.