• 한국초전도학회:학술대회논문집
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• v.10
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• pp.125-127
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• 2000

We report high pressure synthesis of Sr$_{0.9}$Sm$_{0.1}$CuO$_2$. Powder x-ray diffraction showed that the synthesized compounds have infinite layer structure as a major component. Slow heating at the first stage of heating processes after pressurization resulted in several larger grains. The largest grain was found to have the longest edge length of about 100 micrometer. Through magnetic property measurement in superconducting state, we found that pinning in this compound has substantial difference from that of La doped infinite layer, which has no unpaired spin at Sr site.

• Journal of the Korean Wood Science and Technology
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• v.44 no.4
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• pp.539-550
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• 2016

The objective of this research was to evaluate physical and mechanical properties of three species of Styrax woods from North Tapanuli in Indonesia. The woods were more than 15 years old. Physical properties such as specific gravity, green moisture content, and volume shrinkage were determined by the procedures based on BS-373 standard for small clear specimen. Furthermore, mechanical properties, including modulus of rupture, modulus of elasticity, compression parallel to grain and hardness were also tested according to the standard. Along the stem direction, the edge section had better properties compared with those near the pith section. And the base section had also better properties than upper section. Based on the specific gravity, all of the Styrax woods in this research were classified into III-IV strength classes. A good dimensional stability was demonstrated by the value of the tangential and radial ratio which reached one. With the consideration of the mechanical properties, Styrax woods were suitable use for raw materials of light construction, furniture and handy craft.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.83-83
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• 2011

본 연구에서는 p-type Si (100) 위에 분자선 에피택시 성장방법으로 ZnO 완충층이 삽입된 ZnO 박막을 성장시켰다. ZnO 완충층은 Zn 셀 셔터의 열림/닫힘을 반복하는 성장 멈춤법으로 성장되었다. Zn 셀 셔터의 열림 시간은 4분, 2분, 1분이며 닫힘 시간은 2분으로 동일하게 유지하였다. 이러한 과정은 각각 5, 10, 20회로 반복되었으며 ZnO 완충층을 성장한 후 ZnO 박막은 기존의 분자선 에피택시 방법으로 성장되었다. ZnO 박막의 구조적, 광학적 특성은 field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), photoluminescence (PL)로 조사하였다. SEM 측정결과 성장 멈춤 횟수가 증가함에 따라 ZnO 박막의 표면은 섬(island) 구조에서 미로(maze) 구조로 변화하였고, XRD 측정결과 full-width at half-maximum (FWHM) 이 감소하고 결정립 크기(grain size)가 증가하였다. 그리고 PL 측정결과 성장 멈춤 횟수가 증가함에 따라 near-band-edge emission (NBE) 피크의 세기가 증가하였고 deep-level emission (DLE) 피크의 위치는 오렌지 발광에서 녹색 발광으로 청색편이(blue-shift)하였다.

• Journal of the Mineralogical Society of Korea
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• v.13 no.4
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• pp.196-204
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• 2000

We present characteristics of hydrothermal chlorite and its interstratification with 7-$\AA$ mineral phase that occur in the propylitic alteration zone of the Bobae sericite deposit formed in rhyodacitic tuff. Chlorite is found as disseminated fine-grained aggregate or replacement materials of precursor minerals such as Fe-oxides and amphibole. Based on X-ray diffraction(XRD), all chlorites belong to IIb polytype and the (060) reflections averaging $1.53~1.54\AA$ indicate a trioctahedral structure. Chemical compositions of chlorite show that the Fe/(Fe+Mg) values are mostly in the range of 0.44~0.53, and cation deficiencies in octahedral sites range from 0.06 to 0.37. Under scanning electron microscope(SEM) chlorite occurs as well-crystallized aggregates and is subparallely stacked in interstices or between grain boundaries of associated minerals. transmission electron microscopic(TEM) images reveal that chlorite shows regular layers with $14-\AA$ spacings, locally interstratified with $7-\AA$ or $21-\AA$ periodicities. The $21- \AA$ periodicity corresponds to the sum of the $d_{001}$ values of chlorite and $7-\AA$ phase. The chlorite packet coexisting with 7-$\AA$ layers displays abundant defects such as edge dislocations and layer terminations. Selected-area electron diffraction(SAED) indicates that chlorite and $7-\AA$ phase are randomly interstratified in the mixed-layer areas. We propose a lateral change of layers for the polymorphic transition of $7-\AA$ phase to chlorite.e.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.2
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• pp.32-36
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• 2001

We investigate the surface order, defects and morphology of hexagonal columnar mesophases, Having a crown ether at one end which forms the center of the column and three fluorinated tails at the other, The orientation of the columns was successfully controlled by surface anchoring: Columns were aligned perpendicularly to an evaporated carbon surface, and the planar alignment do asymmetric compounds was induced by a water surface. TEM images show that there is a high degree of perfection in the packing do the cylinders. The hexagonal columnar mesophase (F(sub)h) was confirmed by direct images and the corresponding electron diffractions, where ordered cylindrical moieties are packed on a hexagonal lattice. The column of 12F8-ABG-15C5 was much straighter, compared with that of 12F8-AG-B15C5, resulting from the degrees of regular stacking. Elementary edge dislocation, grain boundary and +1/2 disclination have been observed, although the defects are generally rare.

• Journal of Advanced Marine Engineering and Technology
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• v.10 no.1
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• pp.65-73
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• 1986

Surface fatigue crack propagation tests by plane bending fatigue were conducted on the welding specimens of an aluminium alloy, A5083-0, having an edge through thickness notch to study the fatigue crack growth characteristics. Moreover, the experiments were performed in order to clarify the fatigue crack initiation and growth. The properties of fatigue crack growth were quantitatively inspected in welded metal, heat-affected zone and base metal of the welding specimens. The main results obtained are summarized as follows: 1. It is found that the hardness distributions of A5083-0 aluminium alloy weldments are quite different with those of steel material weldments, so that the hardness distribution becomes lower in the following order: base metal, heat-affected zone and weld metal. 2. It is observed that the grain size of this specimen weldment appears to be almost equal to the base metal, when TIC welding method is adopted. 3. In a surface fatigue crack initiation and growth, the fatigue crack does not begin by opening-closing mechanism until hardening is saturated at the crack tip. 4. The fatigue crack growth characteristics of A5083-0 alluminium alloy weldments can be concluded.$${\frac{da}{dn}}=C({\Delta}K)^n=3.8{\times}10^{-9}{({\frac}{1}{2}{\Delta}S_t{\sqrt{{\pi}a}})}^{2.4}$$

• Electrical & Electronic Materials
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• v.7 no.4
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• pp.331-340
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• 1994

Polysilicon on insulator has been recrystallized by zone melting recrystallization method with graphite strip heaters. Experiments are performed with non-seed SOI structures. When the capping layer thickness of Si$\_$3/N$\_$4//SiO$\_$2/ is 2.0.mu.m, grain boundaries are about 120.mu.m spacing and protrusions reduced. After the seed SOI films are annealed at 1100.deg. C in NH$\_$3/ ambient for 3 hours, the recrystallized silicon surface has convex shape. After ZMR process, the tensile stress is 2.49*10$\^$9/dyn/cm$\^$2/ and 3.74*10$\^$9/dyn/cm$\^$2/ in the seed edge and seed center regions. The phenomenon of convex shape and tensile stress difference are completely eliminated by using the PSG/SiO$\_$2/ capping layer. The characterization of SOI films are showed that the SOI films are improved in wetting properties. N channel SOI MOSFET has been fabricated to investigate the electrical characteristics of the recrystallized SOI films. In the 0.7.mu.m thickness SOI MOSFET, kink effects due to the floating substrate occur and the electron mobility was calculated from the measured g$\_$m/ characteristics, which is about 589cm$\^$2//V.s. The recrystallized SOI films are shown to be a good single crystal silicon.

• Journal of Surface Science and Engineering
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• v.52 no.6
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• pp.310-315
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• 2019

The use of a silicon carbide (SiC)-based composite ceramic layer for the mold of a curved cover glass was demonstrated. The stress of SiC/VDR/graphite-based mold structure was evaluated via finite element analysis. The results revealed that the maximum tensile stress primarly occured at the edge region. Moreover, the stress can be reduced by employing a relatively thick SiC coating layer and, therefore, layers of various thicknesses were deposited by means of chemical vapor deposition. During growth of the layer, the orientation of the facets comprising the SiC grain became dominant with additional intense SiC(220) and SiC(004). However, the roughness of the SiC layer increased with increasing thickness of the layer and. Hence, the thickness of the SiC layer needs to be adjusted by values lower than the tolerance band of the curved cover glass mold.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.9
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• pp.818-824
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• 2008

The Separated Pulsed Laser Deposition (SPLD) technique uses two chambers that are separated by a conic metallic wall with a central orifice. The pressures of ablation chamber and deposition chamber were controlled by the differential vacuum system. We deposited zinc oxide (ZnO) thin films by SPLD method to obtain high quality thin films. When the bias voltage of +500 V was applied between a substrate and an orifice, the ZnO thin film was deposited efficiently. The deposited ZnO thin film at ablation chamber gas pressure of Ar 5 mTorr showed the sharpest ultraviolet absorption edge indicatory the band gap of about 3.1 eV. ZnO thin films were deposited using effect of electric and magnetic fields in the SPLD method. E${\times}$B drift happened by an electric fields and a magnetic fields, activated plasma plume, as a result the film surface became very smooth. When the bias voltage of +500 V and magnet of 0,1 T were applied the ZnO thin films surface state showed high quality. Grain size was 41.99 nm and RMS was 0.84 nm.

• Bulletin of the Korean Chemical Society
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• v.22 no.2
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• pp.154-158
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• 2001

The steps for the generation of very thin GaN films on ultrathin AlN/6H-SiC surface by alternating a pulsative supply (APS) of trimethyl gallium and NH3 gases have been examined by ASED-MO calculations. We postulate that the gallium cul ster was formed with the evaporation of CH4 gases via the decomposition of trimethyl gallium (TMG), dimethyl gallium (DMG), and monomethyl galluim (MMG). During the injection of NH3 gas into the reactor, the atomic hydrogens were produced from the thermal decomposition of NH3 molecule. These hydrogen gases activated the Ga-C bond cleavage. An energetically stable GaN nucleation site was formed via nitrogen incorporation into the layer of gallium cluster. The nitrogen atoms produced from the thermal degradation of NH3 were expected to incorporate into the edge of the gallium cluster since the galliums bind weakly to each other (0.19 eV). The structure was stabilized by 2.08 eV, as an adsorbed N atom incorporated into a tetrahedral site of the Ga cluster. This suggests that the adhesion of the initial layer can be reinforced by the incorporation of nitrogen atom through the formation of large grain boundary GaN crystals at the early stage of GaN film growth.