• Proceedings of the Korean Magnestics Society Conference
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• 2010.06a
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• pp.79-79
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• 2010

Semimetallic bismuth (Bi) has been extensively investigated over the last decade since it exhibits very intriguing transport properties due to their highly anisotropic Fermi surface, low carrier concentration, long carrier mean free path l, and small effective carrier mass $m^*$. In particular, the great interest in Bi nanowires lies in the development of nanowire fabrication methods and the opportunity for exploring novel low-dimensional phenomena as well as practical application such as thermoelectricity[1]. In this work, we introduce a self-assembled interconnection of nanostructures produced by an on-film formation of nanowires (OFF-ON) method in order to form a highly ohmic Bi nanobridge. A Bi thin film was first deposited on a thermally oxidized Si (100) substrate at a rate of $40\;{\AA}/s$ by radio frequency (RF) sputtering at 300 K. The sputter system was kept in an ultra high vacuum (UHV) of $10^{-6}$ Torr before deposition, and sputtering was performed under an Ar gas pressure of 2m Torr for 180s. For the lateral growth of Bi nanowires, we sputtered a thin Cr (or $SiO_2$) layer on top of the Bi film. The Bi thin films were subsequently put into a custom-made vacuum furnace for thermal annealing to grow Bi nanowires by the OFF-ON method. After thermal annealing, the Bi nanowires cannot be pushed out from the topside of the Bi films due to the Cr (or $SiO_2$) layer. Instead, Bi nanowires grow laterally as a mean s of releasing the compressive stress. We fabricated a self-assembled Bi nanobridge (d=192 nm) device in-situ using OFF-ON through annealing at $250^{\circ}C$ for 10hours. From I-V measurements taken on the Bi nanobridge device, contacts to the nanobridge were found highly ohmic. The quality of the Bi nanobridge was also proved by the high MR of 123% obtained from transverse MR measurements. These results manifest the possibility of self-assembled nanowire interconnection between various nanostructures for a variety of applications and provide a simple device fabrication method to investigate transport properties on nanowires without complex patterning and etching processes.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.4 s.37
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• pp.281-287
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• 2005

in-situ electromigration test was carried out for edge drift lines of eutectic SnPb solder using Scanning Electron Microscopy (SEM). The electromigration test for the eutectic SnPb solder sample was conducted at temperature of $90^{\circ}C$ and the current density of $6{\times}10^4A/cm^2$. Edge drift at cathode and hillock growth at anode were observed in-situ in a SEM chamber during electromigration test. It was clearly revealed that eutectic SnPb solder lines has an incubation stage before void formation during electromigration test, which seemed to be related to the void nucleation stage of flip chip solder electromigration behaviors.

• Journal of the Korean Vacuum Society
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• v.8 no.1
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• pp.20-25
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• 1999

The effect of different plasma surface preparation and oxidation processes for the formation of $SiO_2-Si$(100) interfaces was studied using angle resolved uv-photoelectron spectroscopy. The surface preparation processes included ex situ preclean as well as in situ hydrogen plasma, which were compared to the processes of UHV annealing at high temperature. The spectral position of the oxide valence band features, with respect to the Fermi level. Were found to shift according to the different processes of surface preparation and oxidation. The shifts were analyzed in terms of band bending in the Si. Origins of the spectral shifts were considered to include defects at the $SiO_2Si$ interfaces and surface morphology(roughness) dependent on the surface preparation processes. From comparison of the ARUPS results of the various processes, it was concluded that the interface bonding of the silicon oxide-showed the lowest band bending.

• Korean Journal of Materials Research
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• v.8 no.10
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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.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.46.3-46.3
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• 2015

As theoretical and empirical studies have pointed out, galaxy mergers play a pivotal role in galaxy mass assembly histories. Its contribution is considered to be more significant in more massive galaxies. In order to quantitatively understand the origin of stellar components in galaxies, we investigated stellar mass assembly histories as a function of galaxy and halo mass using semi-analytic approaches. In this study, we found that the most massive galaxies (log $M/M_{\odot}$ ~ 11.75 at z = 0), which are mostly the brightest cluster galaxies, obtain roughly 70% of their stellar components via mergers. The role of mergers monotonically declines with galaxy mass: less than 20% for log $M/M_{\odot}$ = 10.75 at z = 0. The contribution of galaxy mergers to stellar mass growth decays more slowly than that of in-situ star formation. Therefore, merger accretion becomes a dominant channel for stellar mass growth of the most massive group since z~2. However, when it comes to central galaxies in haloes less massive than $10^{13}_{\odot}$, star formation is always dominant.

• Tribology and Lubricants
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• v.11 no.5
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• pp.177-183
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• 1995

Recent work with phosphate esters has shown that a lubricious polymeric film can formed from the vapor phase on interacting during and sliding. This lubrication technique has led to methods to reduce friction and wear to very low values at high temperatures up to 700$^{\circ}$C. Preliminary with synthetic tri aryl phosphates are very promising. The vaporized lubricant forms a polymeric film on the sliding and rolling surfaces reducing the coefficient of friction below 0.05. In-situ formation of the polymeric films shows that the polymer that is formed on the surface exists in different states depending on surface temperature.

• Tribology and Lubricants
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• v.11 no.2
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• pp.34-43
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• 1995

The boundary films formed in sliding on steel surfaces were characterized using various lubricants. The mechanism of boundary film formation and loss was investigated over a range of temperature. The thickness of the boundary films was monitored in-situ by an ellipsometer, and the composition of the films was analyzed by XPS. The performance of the lubricants is closely associated with boundary film forming ability. In order to achieve high load carrying capacity, a boundary film must be formed on the surface. Sliding is necessary to form the films and some time is also required. As temperature increases, chemical reactivity increases the film formation rate, while the film removal rate increases due to thg decrease of durability of the boundary film material. There is a balance between these two competing mechanisms and this balance is reflected in the boundary film thickness.

• Journal of Korea Foundry Society
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• v.18 no.6
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• pp.593-603
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• 1998

Commercial ductile iron was coated with titanium and aluminum powders by low pressure plasma spraying and then irradiated with a $CO_2$ laser to produce anti-corrosive TiC composite layer. TiC carbides were precipitated homogeneously in a laser alloyed layer by in-situ reaction between carbon existed in the base metal and titanium with thermal sprayed coating. The formation of gas pores and brittle limited mixing zone with ledeburite microstructure in TiC composite layer were surpressed by the complementary alloying of aluminum. The hardness of TiC composite layer obtained by addition of titanium and aluminum was between 600 and 660 Hv, which was three times as high as the hardness of ferritic ductile iron. From the results of isothermal oxidation at 1123k for 24 hours in air, high temperature oxidation resistance of the TiC composite layer with aluminum was improved and doubled when compared with the TiC composite layer without aluminum.

• Economic and Environmental Geology
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• v.38 no.2 s.171
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• pp.165-176
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• 2005

Natural gas in deep sediment may occur in three phases based on the physical and chemical conditions. If the concentration of gas in pore water is less than the solubility, gas is dissolved. If the concentration of gas is greater than its solubility (water is saturated or supersaturated with gas), gas occurs as a fee gas below the gas hydrate stability Lone (GHSZ) and is present as solid hydrate within the GHSZ. The knowledge of gas concentration in deep sediment appears critical to determine the phase of natural gases and to understand the formation and distribution of gas hydrate. However, reliable data on gas concentration are usually available only from the upper section of marine sediment by the headspace gas technique, which is widely used for sampling of gases from the sediments. The headspace gas technique represents only a fraction of gases present in situ because sediments release most of the gases during recovery and sampling. The PCS (Pressure Core Sampler) is a downhole tool developed to recover a nominal $1{\cal}m$ long, $4.32{\cal}cm$ diameter core containing $1,465cm^3$ of sediment, pore water and gas at in situ pressure up to 68.9 MPa. During Leg 204, the PCS was deployed at 6 Sites. In situ methane gas concentration and distribution of gas hydrate was measured by using PCS tool. Characteristics of methane concentration and distribution is different from site to site. Distribution of gas hydrate in the study area is closely related to characteristics of in situ gas concentration measured by PCS.

• Journal of the Korean Vacuum Society
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• v.4 no.S1
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• pp.113-117
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• 1995

MOCVD of Cu films were carried out on gold-TiN(1000$\AA$)/Ti/Si wafers from hexafluoroacetylacetonate-Cu(l) vinyltrimethylsilane, Cu(l)(hafac)(vtms), in a small cold-wall type reactor. Effects of the substrate and bubbler temperatures on the film growth rate were studied, and a film with $\rho$=1.8$\pm$0.1$\mu$$\Omega$.cm could be deposited 150nm/min at Ts=200 and Tb=$30^{\circ}C$, respectively. The initial stage of the film formation was also investigated by in-situ laser reflectivity monitoring combined with SEM observations, based on which variations in the film properties depending on the growth conditions were discussed in terms of the nucleation rate and grain size.