• Korean Journal of Materials Research
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• v.11 no.12
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• pp.1014-1019
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• 2001

The diamond thin film was deposited on Si(100) substrate from$CH_3OH/H_2O$mixtured gas using a hot filament chemical vapor deposition(HFCVD) method. The deposition condition for samples has been varried with the$CH_3OH/H_2O$composition. Scanning electron microscopy(SEM) and Raman spectroscopy has been employed for the sample analysis. The diamond sample has been obtained below 20Pa with$CH_3OH/H_2O$mixtured gas. The crystallinity of diamond film improved as the composition $CH_3OH$decreases from 60Vol% to 52Vol%, and the sample structure changed from the cauliflower to the diamond structure. But the sample structure was becomes cauliflower at 50Vol% of in$CH_3OH$ in the $CH_3OH/H_2O$. It was shown that the$CH_3OH$ has threshold composition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.66-69
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• 2001

Effect of $N_2$ flow rate on properties of GaN thin films grown by plasma-enhanced molecular beam epitaxy(PEMBE) was discussed to optimize the quality of thin films. It was found that at low $N_2$ flow rate indicating high III/V flux ratio, the growth rate of GaN thin films was controlled by $N_2$ flux, and at high $N_2$ flow rate the growth rate was not controlled by $N_2$ flux any longer. It was also found that III/V flux ratio affected film quality. The film grown at higher $N_2$ flow rate showed low background carrier concentration, higher carrier mobility, and narrow FWHM in band-edge emission of low temperature PL. It is thought that the film in more Ga flux region was grown by 2-dimensional layer-by-layer growth mode, and the film in more nitrogen region was grown by 3-D island growth mode. All samples exhibited a good crystallinity.

• Korean Journal of Materials Research
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• v.20 no.7
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• pp.351-355
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• 2010

Transparent conducting aluminum-doped ZnO thin films were deposited using a sol-gel process. In this study, the important deposition parameters were investigated thoroughly to determine the appropriate procedures to grow large area thin films with low resistivity and high transparency at low cost for device applications. The doping concentration of aluminum was adjusted in a range from 1 to 4 mol% by controlling the precursor concentration. The annealing temperatures for the pre-heat treatment and post-heat treatment was $250^{\circ}C$ and 400-$600^{\circ}C$, respectively. The SEM images show that Al doped and undoped ZnO films were quite uniform and compact. The XRD pattern shows that the Al doped ZnO film has poorer crystallinity than the undoped films. The crystal quality of Al doped ZnO films was improved with an increase of the annealing temperature to $600^{\circ}C$. Although the structure of the aluminum doped ZnO films did not have a preferred orientation along the (002) plane, these films had high transmittance (> 87%) in the visible region. The absorption edge was observed at approximately 370 nm, and the absorption wavelength showed a blue-shift with increasing doping concentration. The ZnO films annealed at $500^{\circ}C$ showed the lowest resistivity at 1 mol% Al doping.

• Applied Chemistry for Engineering
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• v.8 no.1
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• pp.84-91
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• 1997

Diamond film was deposited on Mo substrate at atmospheric pressure using a combustion flame apparatus with the addition of $H_2$. With the substrate temperature, the nucleation density of the substrate was increased. At temperatures above $1000^{\circ}C$, some of diamond was partly converted into graphite and etched by hydrogen atoms. With an increase of the $C_2H_2/O_2$ ratio, the nucleation density was increased. But crystals were cauliflower-shaped and a large number of amorphous carbon were deposited. With the addition of $H_2$, the nucleation density of diamond was increased by the improvement of surface activity. Diamond film of high crystallinity was deposited by etching amorphous carbon. With an increase of deposition time, the thickness of diamond film was increased.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.305-320
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• 1999

It was grown Er2O3 doped LiNbO3 single crystal thin films with high crystal quality by liquid phase epitaxial (LPE) method. Er2O3 was doped with a concentration of 1, 3, and 5 mol% respectively. After the growth of single crystal thin film, we examined the crystallinity and the lattice mismatch along the c-axis between the film and the substrate with the variation of Er2O3 dopant using X-ray double crystal technique. There were no lattice mismatches along the c-axis for the undoped and the films doped with 1 and 3 mol% of Er2O3. For 5 mol% of Er2O3 doped film, there was a lattice mismatch of 7.86x10-4nm along the c-axis.

• Journal of the Korean institute of surface engineering
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• v.44 no.6
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• pp.260-263
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• 2011

GZO/ITO double layered films were deposited on unheated non-alkali glass substrates by RF magnetron sputtering using an ITO ($SnO_2$: 10 wt%) and GZO($Ga_2O_3$: 5.57 wt%) ceramic targets, respectively. The electrical resistivity of GZO/ITO films depends on the thickness ratio between the GZO film and ITO film. With increasing ITO film thickness, the resistivity of GZO/ITO films decreased which due to large increase in the Hall mobility. Also, the crystallinity of GZO/ITO film was improved with an increase in ITO thickness which was evaluated by X-ray diffraction. The average transmittance of the films was more than 85% in the visible region, which is slightly higher than ITO single layer films.

• Korea-Australia Rheology Journal
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• v.13 no.1
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• pp.1-12
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• 2001

This paper describes the application of our recently developed two-phase model for flow-induced crystallization (FIC) to the simulation of fiber spinning and film blowing. 1-D and 2-D simulations of fiber spinning include the combined effects of (FIC), viscoelasticity, filament cooling, air drag, inertia, surface tension and gravity and the process dynamics are modeled from the spinneret to the take-up roll device (below the freeze point). 1-D model fits and predictions are in very good quantitative agreement with high- and low-speed spinline data for both nylon and PET systems. Necking and the associated extensional softening are also predicted. Consistent with experimental observations, the 2-D model also predicts a skin-core structure at low and intermediate spin speeds, with the stress, chain extension and crystallinity being highest at the surface. Film blowing is simulated using a "quasi-cylindrical" approximation for the momentum equations, and simulations include the combined effects of flow-induced crystallization, viscoelasticity, and bubble cooling. The effects of inflation pressure, melt extrusion temperature and take-up ratio on the bubble shape are predicted to be in agreement with experimental observations, and the location of the frost line is predicted naturally as a consequence of flow-induced crystallization. An important feature of our FIC model is the ability to predict stresses at the freeze point in fiber spinning and the frost line in film blowing, both of which are related to the physical and mechanical properties of the final product.l product.

• Korean Journal of Materials Research
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• v.22 no.8
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• pp.385-389
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• 2012

Significant improvements in the switching voltage distribution are required for the development of unipolar resistive memory devices using $MnO_x$ thin films. The $V_{set}$ of the as-grown $MnO_x$ film ranged from 1 to 6.2 V, whereas the $V_{set}$ of the oxygen-annealed film ranged from 2.3 to 3 V. An excess of oxygen in an $MnO_x$ film leads to an increase in $Mn^{4+}$ content at the $MnO_x$ film surface with a subsequent change in the $Mn^{4+}/Mn^{3+}$ ratio at the surface. This was attributed to the change in $Mn^{4+}/Mn^{3+}$ ratios at the $MnO_x$ surface and to grain growth. Oxygen annealing is a possible solution for improving the switching voltage distribution of $MnO_x$ thin films. In addition, crystalline $MnO_x$ can help stabilize the $V_{set}$ and $V_{reset}$ distribution in memory switching in a Ti/$MnO_x$/Pt structure. The improved uniformity was attributed not only to the change of the crystallinity but also to the redox reaction at the interface between Ti and $MnO_x$.

• Korean Journal of Environmental Biology
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• v.17 no.3
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• pp.249-255
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• 1999

The effect of surface roughness on biodegradability of poly (3-hydroxybutyrate) was investigated. The PHB film prepared by cooling the molten polymer slowly ($-0.5^{\circ}C$/min) had higher crystallinity and melting temperature than that prepared by quenching into liquid nitrogen followed by annealing at $90^{\circ}C$ for 2 hours. However, the former sample was found to degrade faster than the latter due to presence of microscopic crack. Roughening the surface of a PHB film by hot pressing under a coarse surfaced plate accelerated the bioerosion considerably of the sample in comparison with the sample having the same thermal history but smooth surface.

• Korean Journal of Materials Research
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• v.12 no.9
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• pp.718-723
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• 2002

$Ti_{1-x}$ $Al_{ x}$N thin films as barrier layer for memory devices application were deposited by reactive magnetron sputtering. The crystallinity, micro-structure, oxidation resistance and oxidation mechanism of films were investigated as a function of Al content. Lattice parameter and grain size of thin films were decreased with increasing the Al content Oxidation of the film with higher Al content is slow and then, total oxide thickness is thinner than that of lower Al content film. Oxide layer formed on the surface is AlTiNO layer. Oxidation of $Ti_{1-x}$ /$Al_{x}$ N barrier layer is diffusion limited process and thickness of oxide layer with oxidation time increased with a parabolic law. The activation energy of oxygen diffusion, Ea and diffusion coefficient, D of $Ti_{0.74}$ /X$0.74_{0.26}$N film is 2.1eV and $10^{-16}$ ~$10^{-15}$ $\textrm{cm}^2$/s, respectively. $_Ti{1-x}$ /$Al_{x}$ XN barrier layer showed good oxidation resistance.