• Journal of Magnetics
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• v.11 no.1
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• pp.25-29
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• 2006

Recent experiments have demonstrated high TMR ratios in MTJs with the MgO barrier [1,2]. The CoFeB/MgO/CoFeB junctions showed better properties than the CoFe/MgO/CoFe junctions because the MgO layer had a good crystalline structure with (001) texture and smooth and sharp interface between CoFeB/MgO [3]. The amorphous CoFeB with 20 at%B starts the crystallization at $340^{\circ}C$ [4] and this crystallization of the CoFeB helps obtaining the high TMR ratio. In this work, the compositional changes in the MgO barrier and at the interface of CoFeB/MgO/CoFeB after the CoFeB crystallization were studied in annealed MTJs. XPS depth profiles were utilized. TEM analyses showed that the MgO barrier had (100) texture on CoFeB in the junctions. B in the bottom CoFeB layer diffused into the MgO barrier and B-oxide was formed at the interface of CoFeB/MgO/CoFeB after the CoFeB crystallization.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.2
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• pp.111-115
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• 2000

$BaTIO_3$ thin films were prepared on (100) $BaTIO_3$ substrates by coating- pyrolysis process using metal-organic compounds of Ba and Ti. The amorphous films prefired at $450^{\circ}C$were crystallized above $700^{\circ}C$ under oxygen partial pressure of $2\times 10^{-4}$. The lattice parameters of the perpendicular axis for the $BaTIO_3$ thin films heat-treated below $800^{\circ}C$ were closer to a value of cubic $BaTIO_3$, whereas those above $800^{\circ}C$ were closer to a value of tetragonal BaTiG. The results of XRD P scan and pole-figure analyses indicated that BaTiO, thin films have an epitaxial relationship with the $SrTiO_3$ substrates. The $BaTIO_3$thin films annealed at$800^{\circ}C$ showed the surface with island-like grains about 0.4$mu \textrm{m}$ and the cross section of 0.8 $mu \textrm{m}$ thickness with granular grains.

• Polymer(Korea)
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• v.24 no.5
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• pp.638-645
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• 2000

Linear and star-shaped, poly(lactic acid) (PLA) stereo-block copolymers were synthesized by sequential polymerization of DL-lactic acid and L-lactide in the presence of diol or polyol compounds. The molecular weight of block copolymers could be controlled to some extent by the variation of alcohol content. These block copolymers had relatively narrow molecular weight distributions. The glass transition temperature and melting temperature of block copolymers appeared at around 5$0^{\circ}C$ and 100~14$0^{\circ}C$, respectively. The block copolymers were found to crystallize even at the high D-stereoisomer concentration of 35 mol%, in contrast to the amorphous nature of the random copolymer with similar composition. Also we could observe the crystallinity of PLA stereo-block copolymers varying with annealing temperature and time.

• Journal of the Korean Vacuum Society
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• v.18 no.1
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• pp.49-53
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• 2009

The chemical properties of SiOC film was studied for inter-layer insulator. SiOC film was formed with non polarity due to the appropriate union by the alkyl and hydroxyl group. An amorphous structure of non polarity can induce the low dielectric constant materials. The chemical properties of thin film can define the bonding structure owing to the ionic variation, and the analysis of chemical properties was researched by the carbon content using the FTIR spectra, and induced the film with non polarity. The electrical properties is the electron flow, and is always not the same as the chemical properties. The electrical properties of SiOC film with various flow rate ratios was analyzed and researched the correlation between the chemical properties. SiOC film showed the increasing of the leakage current after annealing process, and abruptly increased the carbon content at some samples. But the sample with increasing the carbon content decreased the leakage current. It means that the chemical properties is not the same as the electrical properties, and the carbon is related with the variation of the bonding structure, and does not contribute the current flow.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.3
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• pp.428-436
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• 1997

Hexacelsian ($BaO{\cdot}Al_2O_3{\cdot}2SiO_2$) powder was prepared by a solution-polymerization route employing PVA solution as a polymeric carrier. A fine amorphous-type hexacelsian powder with an average particle size of 0.8 $\mu \textrm{m}$ and a BET specific surface area of $63 \textrm{m}^2$/g was made by a ball-milling the powder precursor for 12 h after calcination at $800^{\circ}C$ for :1 h. A densified hexacelsian was obtained through sintering at $1550^{\circ}C$ for 2 h under an air atmosphere. The $\alpha\longleftrightarrow\beta$ and $\beta\longleftrightarrow\gamma$ displacive phase transformation in polycrystalline hexacelsia,n was examined by using dilatometry and differential scanning calorimtry. The reconstructive transformation between hexacelsian and celsian was obtained by annealing at $1600^{\circ}C$ for 72h. Volume contraction of 5.6% was accompanied by the reconstructive transformation.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.1
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• pp.8-12
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• 1999

$\textrm{WO}_3$ semiconductive film, which is known to have a sensitivity on $\textrm{NO}_X$ gas was prepared on 8YSZ (8% Yttria stabilized $\textrm{ZrO}_2$) ionic conductor substrate that has oxygen ion pumping effect. Microstructure and electrical properity, especially $\textrm{NO}_X$ sensitivity as a function of DC voltage applied to 8YSZ substrate was examined. When the $\textrm{WO}_3$ film was annealed, it showed amorphous structure, while crystallization was occurred at $600^{\circ}$C revealing orthorhombic phase of $\textrm{WO}_3$. As the annealing temperature increases, (111) and (001) peaks of $\textrm{WO}_3$ film was enhanced. At $400^{\circ}C$ when DC voltage was applied, comparing with no DC bias, more stable and large response characteristics was showed, and the best sensitivity was observed at 2V. Recovery characteristics of NO gas was much better that that of $\textrm{NO}_2$ gas.

• Journal of the Korean Electrochemical Society
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• v.18 no.1
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• pp.31-37
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• 2015

Composition-controlled ternary components chalcogenides germanium tin sulfide ($Sn_xGe_{1-x}S$) nanoparticles were synthesized by a novel gas-phase laser photolysis reaction of tetramethyl germanium, tetramethyl tin, and hydrogen sulfide mixture. Subsequent thermal annealing of as-grown amorphous nanoparticles produced the crystalline orthorhombic phase nanoparticles. All these composition-tuned nanoparticles showed excellent cycling performance of the lithium ion battery. The germanium sulfide nanoparticles exhibit a maximum capacity of 1200 mAh/g after 70 cycles. As the tin composition (x) increases, the capacity maintains better at the higher discharge/charge rate. This novel synthesis method of tin germanium sulfide nanoparticles is expected to contribute to expand their applications in high-performance energy conversion systems.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.5
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• pp.401-406
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• 2008

Recently, portable magnetic sensors with high sensitivity are strongly required for various applications such as biosensor, nondestructive testing and directional sensor. A novel magnetic sensor system was developed by utilizing giant magnetoimpedance(MI) effect of soft magnetic ribbons. The sensor system consists of sensing head of $Co_{66}Fe_{4}Si_{15}B_{15}$ ribbon having asymmetric MI characteristics through exchange coupling produced by field-annealing in open air and circuit for signal processing. The sensor system showed almost linear characteristics in dynamic range of $-1\;Oe\;{\sim}\;1\;Oe$ and sensitivity of 10.5 V/Oe. The sensor was applicable to nondestructive testing system to detect defects in wire ropes.

• Korean Journal of Materials Research
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• v.8 no.3
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• pp.224-228
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• 1998

Phase transition kinetics of nonstoichiometric amorphous titanium oxide thin films deposited by reactive sputtering was investigated after cooling down with various rate followed by l0min.-3hrs. annealing at $500^{\circ}C$~$600^{\circ}C$ After short duration and fast cooling. Magneli was the only crystalline phase because the oxidation rates of $TiO_{2-x}$, could be relatively slower than that of crystallization. When the films were cooled slowly between $500^{\circ}C$~$300{\circ}C$, Magneli was transformed into an anatase and stabilized, but directly into a rutile under fast cooling. Because the rutile also prevailed after cooling from $600^{\circ}C$, it was concluded that the rutile phase could be formed directly from Magneli as well as converted from the anatase. Changes in volume and surface morphology were observed related to crystallization and oxidation processduring heat treatment.

• Journal of Powder Materials
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• v.23 no.2
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• pp.108-111
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• 2016

$Y_2O_3-H_3BO_3:Eu^{3+}$ powders are synthesized using a mechanical alloying method, and their photoluminescence (PL) properties are investigated through luminescence spectrophotometry. For samples milled for 300 min, some $Y_2O_3$ peaks ([222], [440], and [622]) and amorphous formations are observed. The 300-min-milled mixture annealed at $800^{\circ}C$ for 1 h with Eu = 8 mol% has the strongest PL intensity at every temperature increase of $100^{\circ}C$ (increasing from 700 to $1200^{\circ}C$ in $100^{\circ}C$ increments). PL peaks of the powder mixture, as excited by a xenon discharge lamp (20 kW) at 240 nm, are detected at approximately 592 nm (orange light, $^5D_o{\rightarrow}^7F_1$), 613 nm, 628 nm (red light, $^5D_o{\rightarrow}^7F_2$), and 650 nm. The PL intensity of powder mixtures milled for 120 min is generally lower than that of powder mixtures milled for 300 min under the same conditions. PL peaks due to $YBO_3$ and $Y_2O_3$ are observed for 300-min-milled $Y_2O_3-H_3BO_3$ with Eu = 8 mol% after annealing at $800^{\circ}C$ for 1 h.