• Korean Journal of Metals and Materials
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• v.50 no.10
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• pp.703-710
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• 2012

The effects of the ordering reaction on high temperature mechanical behavior is investigated by tensile tests at $2{\times}10^{-2}/s-3.3{\times}10^{-5}/s$ up to $745^{\circ}C$. The tensile deformed region is examined by differential scanning calorimeter (DSC), TEM, and high resolution neutron diffraction (HRPD). The results showed that a plateau of tensile strength appeared at $150-500^{\circ}C$ whereas the elongation minimum occurred at about $600^{\circ}C$. This suggests that the occurrence of a plateau does not cause the elongation minimum. The temperature of the elongation minimum decreases with the strain rate. HRPD results show a lattice contraction in the tensile deformed specimen at the temperature of the plateau occurring region. The plateau of tensile strength, the lattice contraction, and the occurrence of serration appeared in the same temperature region.

• Applied Microscopy
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• v.40 no.1
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• pp.21-28
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• 2010

In a simulation study of atomic resolution transmission electron microscope images of single layer and bilayer graphene, it is demonstrated that the conventional Bloch wave formulations can be used when high-order Laue zone reflections are properly taken into account in the theory. The simulated images for bilayer graphene show 3-fold rotational lattice symmetry rather than the 6-fold one under certain conditions. This result can be understood as revealed the 3-fold rotational lattice symmetry of bilayer graphene in three dimensions along [0001]. For single layer graphene the observed phase images showing 3-fold rotational lattice symmetry were particularly noted. This phenomenon has been explained by an assumption of the re-configuration of electron density on the surface of graphene. And the matching images have been obtained as simulated with up to the second order Laue zone reflections only, reflecting the re-configuration of electrons on the surface.

• Journal of the Korean Magnetics Society
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• v.24 no.2
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• pp.51-55
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• 2014

The $Fe_3O_4$ nanoparticle was synthesized by the hot-injection method while varying the injection time of the precursor solution. The crystal structure was determined to be cubic inverse spinel with space group of Fd-3m based on X-ray diffraction (XRD) measurements and the morphology of the prepared $Fe_3O_4$ nanoparticle was studied with a high-resolution transmission electron microscope (HR-TEM). When the precursor solution was injected for 0.5 min, the size of the $Fe_3O_4$ nanoparticle was 7.63 nm, while the size of the obtained particle was 21.27 nm with the injection time of 60 min. The magnetic properties of the prepared $Fe_3O_4$ nanoparticle were investigated by both vibrating sample magnetometer (VSM) and $^{57}Co$ M$\ddot{o}$ssbauer spectroscopy at various temperatures. From the hyperthermia measurement, we observed that the temperature of the $Fe_3O_4$ nanoparticle powder reached around $120^{\circ}C$ under 250 Oe at 50 kHz, when the injection time of the precursor solution was 60 min.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.1
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• pp.16-22
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• 2008

We fabricated thermally-evaporated 10 nm-Ni/30 nm and 70 nm Poly-Si/200 nm-$SiO_2/Si$ structures to investigate the thermal stability of nickel silicides formed by rapid thermal annealing(RTA) of the temperature of $300{\sim}1100^{\circ}C$ for 40 seconds. We employed for a four-point tester, field emission scanning electron microscope(FE-SEM), transmission electron microscope(TEM), high resolution X-ray diffraction(HRIXRD), and scanning probe microscope(SPM) in order to examine the sheet resistance, in-plane microstructure, cross-sectional microstructure evolution, phase transformation, and surface roughness, respectively. The silicide on 30 nm polysilicon substrate was stable at temperature up to $900^{\circ}C$, while the one on 70 nm substrate showed the conventional $NiSi_2$ transformation temperature of $700^{\circ}C$. The HRXRD result also supported the existence of NiSi-phase up to $900^{\circ}C$ for the Ni silicide on the 30 nm polysilicon substrate. FE-SEM and TEM confirmed that 40 nm thick uniform silicide layer and island-like agglomerated silicide phase of $1{\mu}m$ pitch without residual polysilicon were formed on 30 nm polysilicon substrate at $700^{\circ}C\;and\;1000^{\circ}C$, respectively. All silicides were nonuniform and formed on top of the residual polysilicon for 70 nm polysilicon substrates. Through SPM analysis, we confirmed the surface roughness was below 17 nm, which implied the advantage on FUSI gate of CMOS process. Our results imply that we may tune the thermal stability of nickel monosilicide by reducing the height of polysilicon gate.

• 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 Vacuum Society
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• v.2 no.4
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• pp.501-506
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• 1993

The spatial potential distribution of electron cyclotron resonance plasma is measured as a function of tehsubstrate DC bias by Langmuir probe method. It is observed that the substrate DC bias changes the slope of the plasma potential near the subsrate, resulting in changes in flux and energy of the impinging ions across plasma $_strate boundary along themagnetric field. The effect of the substrate DC bias on the low-temperature silicon homoepitaxy (below $560^{\circ}C$) is examine dby in situ reflection high energy electron diffraction (RHEED), cross-section transmission electron microscopy (XTEM),plan-view TEM and high resolution transmision electron microscopy(HRTEM). While the polycrystalline silicon layers are grow withnegative substrate biases, the single crystaline silicon layers are grown with negative substrate biases, the singel crystalline silicon layers are grown with positive substrate biases. As the substrate bias changes form negative to positive values, the growth rate decreases. It is concluded that the control of the ion energy during plasma deposition is very important in silicon epitaxy at low temperatures below $560^{\circ}C$ by UHV-ECRCVD.VD.

• Applied Science and Convergence Technology
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• v.26 no.3
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• pp.52-54
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• 2017

An InGaN/GaN multiple quantum well (MQW) structure is grown on a GaN/sapphire template using a plasma-assisted molecular beam epitaxy (PA-MBE). The fluctuation of the quantum well thickness formed from roughly-grown InGaN layer results in a disordered photoluminescence (PL) spectrum. The surface morphologies of the InGaN layers with various In compositions are investigated by reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM). A blurred InGaN/GaN hetero-interface and the non-uniform QW size is confirmed by high resolution transmission electron microscopy (HR-TEM). Inhomogeneity of the quantum confinement results in a degradation of the quantum efficiency even though the InGaN layer has a uniform In composition.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.1
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• pp.27-30
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• 2013

Catalyst-free graphene nano-sheets without substrates have been synthesized using fullerene and a high direct current (dc) pulse in the spark plasma sintering (SPS) process. Graphene nano-sheets were synthesized directly in the gas phase of carbon atoms which are generated from fullerene at a temperature of $600^{\circ}C$. Characterization has been carried out by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD).

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.51-55
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• 2000

Using modified melt-textured grown targets, YBa$_2$Cu$_3$O$_{7-{\delta}}$ thin films were prepared by pulsed laser deposition technique at the laser energy density from 1 J/cm$_2$ to 4 J/cm$_2$. All the films showed c-axis preferred orientations, however, a-axis outgrowths on the film surface were considerably increased with an increase of the laser energy density. To examine the origin of the a-axis outgrowth formation, the microstructures of films deposited at 2 J/cm$_2$ and 4 J/cm$_2$ were investigated using X-ray diffraction, transmission electron microscopy, and high-resolution electron microscopy. It was shown that a significant number of Y$_2$O$_3$ inclusions were formed during the growth of c-axis oriented films at 4 J/cm$_2$. These inclusions formed nucleation sites for the a-axis outgrowths. It is considered that, due to the unstable growth conditions with a high flux density of incident vapor species and the strain induced by the surrounding c-axis films, the Y$_2$O$_3$ inclusions would prefer the nucleation of α-axis grains.

• Toxicological Research
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• v.17 no.3
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• pp.163-165
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• 2001

A patient,58 years of age, with suspected 0/l pneumoconiosis since 1993, complained of a dry cough and exertioning dyspnea for 6 months. He had worked in an asbestos company for more than 20 years from 1974. He was subsequently diagnosed with an interstitial lung disease during an annual special health check-up for asbestos workers. h chest X-ray showed an interstitial lung disease and high-resolution computed tomography (HRCT) showed a round opaque asbestosis with chronic hypersensitivity pneumonitis. A pulmonary function test indicated that the patient had a mild restrictive lung disease with FEV1 1.67 litters and 82% FEVl/FVC. The bronchoalveloar larvage fluid included many asbestos bodies, indicating previous exposure to asbestos. Transmission electron microscopy (TEM) using an energy dispersive X-ray analyzer (EDX) revealed many asbestos bodies consisting of mainly crocidolite fibers (6,071$\times$$10^6$fibers/g of dry lung). The patient had an unusually high asbestos content of 6,112$\times$$10^6$ asbestos fibers/9 of dry lung.