• Korean Journal of Materials Research
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• v.15 no.7
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• pp.439-443
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• 2005

The oxidation behavior and the thermal stability of nanocrystalline Al-25Ti-8Mn intermetallic compound were investigated. $Al_3Ti$ intermetallic compound, which has a potential for high temperature structural material, was fabricated by mechanical alloying(MA) with $8at.\%$ Mn to enhance the thermal stability and ductility. And Al-25Ti-8Mn intermetallic compound was sintered by spark plasma sintering(SPS) at $700^{\circ}C$. After sintering process, cubic $Ll_2$ structure was maintained without phase transformation and the grain size was about 50nm. To investigate the oxidation behavior of the specimens, thermal gravimetric analysis(TGA) was performed at 700, 800, 900, and $1000^{\circ}C$ for 24 h in $O_2$. As the temperature increased from $700^{\circ}C\;to\;900^{\circ}C$ the weight gain of specimens increased. However at $1000^{\circ}C$, unlike the oxidation behavior of $700^{\circ}C\;to\;900^{\circ}C$, the weight gain of specimen decreased drastically and the transition from linear rate region to parabolic rate region occurred rapidly due to the dense $\alpha-Al_2O_3$.

• Korean Journal of Metals and Materials
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• v.46 no.3
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• pp.159-168
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• 2008

Thermally-evaporated 10 nm-Ni/1 nm-Ru/(30 nm or 70 nm-poly)Si structures were fabricated in order to investigate the thermal stability of Ru-inserted nickel monosilicide. The silicide samples underwent rapid thermal anne aling at $300{\sim}1,100^{\circ}C$ for 40 seconds. Silicides suitable for the salicide process were formed on the top of the single crystal and polycrystalline silicon substrates mimicking actives and gates. The sheet resistance was measured using a four-point probe. High resolution X-ray diffraction and Auger depth profiling were used for phase and chemical composition analysis, respectively. Transmission electron microscope and scanning probe microscope(SPM) were used to determine the cross-sectional structure and surface roughness. The silicide, which formed on single crystal silicon and 30 nm polysilicon substrate, could defer the transformation of $Ni_2Si $i and $NiSi_2 $, and was stable at temperatures up to $1,100^{\circ}C$ and $1,100^{\circ}C$, respectively. Regarding microstructure, the nano-size NiSi preferred phase was observed on single crystalline Si substrate, and agglomerate phase was shown on 30 nm-thick polycrystalline Si substrate, respectively. The silicide, formed on 70 nm polysilicon substrate, showed high resistance at temperatures >$700^{\circ}C$ caused by mixed microstructure. Through SPM analysis, we confirmed that the surface roughness increased abruptly on single crystal Si substrate while not changed on polycrystalline substrate. The Ru-inserted nickel monosilicide could maintain a low resistance in wide temperature range and is considered suitable for the nano-thick silicide process.

• Journal of the Korean Ceramic Society
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• v.43 no.2 s.285
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• pp.85-91
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• 2006

Electron Beam Physical Vapor Deposition (EB-PVD) was applied to fabricate a thin film YSZ electrolyte with large area on the porous NiO-YSZ anode substrate. Microstructural and thermal stability of the as-deposited electrolyte film was investigated via SEM and XRD analysis. In order to obtain an optimized YSZ film with high stability, both temperature and surface roughness of substrate were varied. A structurally homogeneous YSZ film with large area of $12\times12\;cm^2$ and high thermal stability up to $900^{\circ}C$ was fabricated at the substrate temperature of $T_s/T_m$ higher than 0.4. The smoother surface was proved to give the better film quality. Precise control of heating and cooling rate of the anode substrate was necessary to obtain a very dense YSZ electrolyte with high thermal stability, which affords to survive after post heat treatment for fabrication a cathode layer on it as well as after long time operation of solid oxide fuel cell at high temperature.

• Analytical Science and Technology
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• v.11 no.2
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• pp.92-95
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• 1998

K-SGICs(synthetic graphite intercalation compounds) were synthesized in a modified two-bulb pyrex tube. The pressure in the two-bulb tube was maintained at approximately $10^{-3}$ torr for the reaction of potassium and graphite. Deintercalation process of the K-SGlCs obtained by the modified method was heat-treated by keeping in liquid paraffin between $25^{\circ}C$ and $1400^{\circ}C$. The thermal stability and the temperature dependence of the K-SGICs were characterized using differential scanning calorimeter(DSC) analyzer. Enthalpy and entropy for K-SGIC formations were calculated by confirming the deintercalation and thermodynamic exothermic reactions depending on the various temperatures. The structure changes and thermal stability of K-SGICs during the deintercalation reaction of potassium ions and the interlayer spaces of the synthetic graphite were identified by X-ray diffraction(XRD).

• Journal of the Korean Society for Railway
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• v.9 no.2 s.33
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• pp.131-136
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• 2006

Most modern railways, especially the high speed railway tracks, use continuous welded rail(CWR) for the less maintenance. For the CWR track has very few expansion joints, track buckling has always been an unpredictable event and it happens mainly by high compressive stress in rail in summer period. Therefore, it is important to understand the variation of rail stress induced by thermal loads which has direct influence on the rail buckling and stability of railway track. This paper describes the experimental investigation of the variation of rail temperature and stress in a high speed railway track on bridge structure. Field measurement was performed to examine the correlation between the rail temperature and rail stress on the Korean High Speed Railway line. Regression functions were derived from measured data to determine the rail stress f3r an arbitrary rail temperature varies from 20 to 50 degree Celsius.

• Journal of Magnetics
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• v.2 no.3
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• pp.86-92
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• 1997

An artificially modulated magnetic Co/Pd multilayer is one of the promising candidates for high density magneto-optic (MO) recording media in the wavelength of a blue laser beam, due to large Kerr rotation angle. However, since the Co/Pd multilayer is a non-equilibrium state in terms of free energy and MO recording is a kind of thermal recording which is conducted around Curie temperature (Tc) of the recording media, the assessment of the thermal stability in the Co/Pd multilayer is crucially important both for basic research and applications. As the parameter of the thermal stability in this research, effective interdiffusion coefficients (Deff) perpendicular to the interface of the Co/Pd multilayers are measured in terms of Ar sputtering pressure and heat treatment temperature. From the results of the research, we find out that the magnetic exchange energy between Co and Pd sublayers strongly affects Deff of the Co/Pd multilayers. This discovery will provide the understanding of the magnetic exchange energy in the effective interdiffusion process of a magnetic multilayer structure and suggest the operating temperature range for MO recording in the Co/Pd multilayer for the basic research and applications, respectively.

• Korean Journal of Materials Research
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• v.18 no.1
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• pp.5-11
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• 2008

Thermally evaporated 10 nm-Ni/1 nm-Au/(30 nm-poly)Si structures were fabricated in order to investigate the thermal stability of Au-inserted nickel silicide. The silicide samples underwent rapid thermal annealing at $300{\sim}1100^{\circ}C$ for 40 seconds. The sheet resistance was measured using a four-point probe. A scanning electron microscope and a transmission electron microscope were used to determine the cross-sectional structure and surface image. High-resolution X-ray diffraction and a scanning probe microscope were employed for the phase and surface roughness. According to sheet resistance and XRD analyses, nickel silicide with Au had no effect on widening the NiSi stabilization temperature region. Au-inserted nickel silicide on a single crystal silicon substrate showed nano-dots due to the preferred growth and a self-arranged agglomerate nano phase due to agglomeration. It was possible to tune the characteristic size of the agglomerate phase with silicidation temperatures. The nano-thick Au-insertion was shown to lead to self-arranged microstructures of nickel silicide.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.366-371
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• 2022

Recently many efforts have been made to develop a novel class of non-fullerene electron acceptor materials for high-performance organic solar cells. In this work, anthraquinone derivatives, TMAQ and THAQ, were prepared and their availability as electron acceptor materials for organic solar cells were investigated in terms of optical, thermal, electrochemical properties, and solar cell devices. Compared to TMAQ, a significant bathochromic shift of absorption band was observed for THAQ owing to intramolecular hydrogen-bond-assisted CT interactions. Thanks to the fused aromatic ring structure and benzoquinone unit, both TMAQ and THAQ exhibited a high thermal stability and an efficient electron reduction process. In particular, the intramolecular O-H---O=C hydrogen bond of THAQ plays an important role in improving the thermal stability and electron reduction properties. In the P3HT:acceptor solar cell system, THAQ-based devices had more than ca. 6 times higher power conversion efficiency than TMAQ -based devices. These results serve as a guide for developing high-efficient anthraquinone-based electron acceptor materials.

• Journal of the Korean Ceramic Society
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• v.41 no.9
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• pp.637-641
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• 2004

We investigated the effects of SiH$_4$ gas on the surface of Hf-silicate films during the deposition of polycrystalline (poly) Si films and the thermal stability of sputtered Hf-silicate films in poly Si/Hf-silicate structure by using High Resolution Transmission Electron Microscopy (HR-TEM) and X-ray Photoelectron Spectroscopy (XPS). Hf-silicate films were deposited by using DC-mag-netron sputtering with Hf target and Si target and poly Si films were deposited at 600$^{\circ}C$ by using Low Pressure Chemical Vapor Deposition (LPCVD) with SiH$_4$ gas. After poly Si film deposition at 600$^{\circ}C$, Hf silicide layer was observed between poly Si and Hf-silicate films due to the reaction between active SiH$_4$ gas and Hf-silicate films. After annealing at 900$^{\circ}C$, Hf silicide, formed during the deposition of poly Si, changed to Hf-silicate and the phase separation of the silicate was not observed. In addition, the Hf-silicate films remain amorphous phase.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.5
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• pp.94-100
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• 1994

The junction failure mechanism of W plugs has not been fully understood while the selective W deposition has been widely used for plugging interconnection lines. In this paper, the thermal stability and junction failure mechanism of sub-micron contacts using selective CVD-W plugs were intensively studied with the metal lines of AISiCu, Ti/AISiCu and TiN/AISiCu. The experimental results showed that the contact chain resistance and leakage current in the AISiCu and Ti/AISiCu metallizations were significantly degraded after annealing. From the SEM analysis, it was found that the junction spiking, due to the Al atoms diffusion along the porous interface between selective CVD-W and contactside wall, caused the junction failure. In constast, there was no degradation of the contact resistance and junction leakage current in TiN/AISiCu metal structu-re. It is believed that the TiN barrier layer could prevent AI(Ti) atoms Fromdiffusing. Therefore, TiN barrier between W plug and Al should be used to impro-ve the thermal stability of sub-micron contacts using the selective CVD-W plugs.