• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.8
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• pp.708-712
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• 2002

The crystallization of amorphous $\alpha$-Fe$_2$O$_3$/$\alpha$-AI$_2$O$_3$(0001) thin films during thermal annealing in air has been studied using real-time synchrotron x-ray scattering. The well aligned (0.02$^{\circ}$/ FWHM) $\alpha$-Fe$_2$O$_3$and Fe$_3$O$_4$interfacial crystallites (50- -thick) coexist on the $\alpha$-AI$_2$O$_3$(0001) in the sputter-grown amorphous films at room temperature. The amorphous precursor is crystallized to the epitaxial $\alpha$-Fe$_2$O$_3$grains in three steps with annealing temperature; i ) the growth of the well aligned $\alpha$-Fe$_2$O$_3$interfacial crystallites, together with the transformation of the Fe$_3$O$_4$crystallites to the $\alpha$-Fe$_2$O$_3$ crystallites, ii ) the growth of the less aligned (3.08$^{\circ}$ FWHM)$\alpha$-Fe$_2$O$_3$grains on the well aligned grains (＞40$0^{\circ}C$), and iii) the nucleation of the other less aligned (1.39$^{\circ}$ FWHM) $\alpha$-Fe$_2$O$_3$grains directly on the $\alpha$-AI$_2$O$_3$substrate (＞$600^{\circ}C$). The effective thickness thinner than 230 may be very useful for enhancing the epitaxial quality of $\alpha$-Fe$_2$O$_3$/AI$_2$O$_3$(0001) thin films.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.6
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• pp.1000-1009
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• 2004

The environment friendly calcareous deposit films were formed on steel plates by electrodeposition technique in natural seawater and synthetic solutions such as dissolved $\textrm{Mg}^{2+}$ and $\textrm{Ca}^{2+}$ ions at various potential conditions. The influence of potential conditions on composition ratio, structure and morphology of the electrodeposited films were investigated by scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray diffractor (XRD). Accordingly, this study was provided a better understanding of the composition between the growth of $\textrm{Mg(OH)}_2$ and that of $\textrm{CaCO}_3$ during the formation of calcareous deposit films on steel substrate under cathodically electrodeposition in synthetic and natural seawater. The results showed that the formation of good overall calcareous deposited film in seawater can be achieved by controlling the Ca/Mg ratio according to interfacial pH with the effective use of the electro deposition technique.

• Journal of Magnetics
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• v.7 no.2
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• pp.51-54
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• 2002

The crystallization of amorphous Ba-ferrite/sapphire(001) thin films was studied in real-time synchrotron x-ray scattering experiments. In the sputter-grown amorphous films, we found the existence of epitaxial $Fe_3O_4$ interfacial crystallites (50-${\AA}$-thick), well aligned $[0.03^circ$full-width at half-maximum (FWHM)] to the sapphire [001] direction. The amorphous precursor was crystallized to epitaxial Ba-ferrite and \alpha-Fe_2O_3$grains in two steps; i) the nucleation of crystalline \alpha-Fe_2O_3$ phase started at $300^circ{C}$ together with the transformation of the $Fe_3O_4$ crystallites to the \alpha-Fe_2O_3$ crystallites, ii) the nucleation of Ba-ferrite phase occurred at temperature above $600^circ{C}$. In the crystallized films irrespective of the film thickness, the crystal domain size of the \alpha-Fe_2O_3$grains was about 250 ${\AA}$ in the film plane, similar to that of the Ba-ferrite grains.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.623-626
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• 1995

High coercivity thin $Fe_{3}O_{4}$ and ${\gamma}-Fe_{2}O_{3}$ films were deposited on Si substrate under well controlled $O_{2}$ partial pressure by dcreactive magnetron sputtering. The coercivity of as-deposited maggnetite films is below 640 Oe. After cxidizing at $360^{\circ}C$ for 10 minutes, the films transform to maghemite ${\gamma}-Fe_{2}O_{3}$ completely, and the coercivity increases greatly to 2100~4120 Oe, depending on modification of not with minor addition of Co or/and Mn. The orign of coercivity enhancement is attributed mainly to magnetic anisotropy arisen from interfacial stress. The addition of 5 at% Co and 5 at% Mn greatly enhances coercivity and squareness ratio. These films are potential for ultra-high density recording applications.

• Journal of the Korean Ceramic Society
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• v.29 no.11
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• pp.863-869
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• 1992

A SOG(spin glass) solution with excellent wetting to Si wafers was prepared by acid-hydrolysis of Si(OEt)4 and Me2Si(OEt)2. The solution was spin coated on Si wafers, and effects of heat treatment of the film were characterized by TG/DTA, FTIR and Ellipsometry. Silica film was obtained by heat treatment at $600^{\circ}C$ within one hour, but heat treatment at 80$0^{\circ}C$ caused interfacial oxidation of the silicon substrate. Unexpectedly silica films with much better adhesion were obtained by curing at $600^{\circ}C$ for over 30 min. than those obtained by thermal oxidation.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.432.1-432.1
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• 2016

We demonstrated that the power conversion efficiency (PCE) of bilayer solar cell was significantly enhanced by inserting interfacial layer between the organic bilayer film and the Al electrode. Moreover, the water contact angle shows that the bilayer solar cells suffer from the undesirable surface component which limits the charge transport to the Al electrode. The AFM measurement has revealed that the pre- and post-thermal annealing treatments results in different morphologies of the interfacial layer which is critical for the higher PCE of the bilayer solar cells. Furthermore we have investigated the electrical properties of the bilayer solar cells and obtained insights into the detailed device mechanisms. The transient photovoltage measurements suggests that the significantly enhanced Voc is caused by reducing the recombination at the interface between the organic films and the Al electrode. By inserting the TiO2 layer between the bilayer film and Al electrode, the open circuit voltage (Voc) was increased from 0.37 to 0.66V. Consequently, the power conversion efficiency (PCE) of bilayer solar cells was significantly enhanced from 1.23% to 3.71%. As the results, the TiO2 interfacial layer can be used to form an ohmic contact layer, serveing as a blocking layer to prevent the penetration of the Al, and to reduce the recombination at the interface.

• Composites Research
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• v.12 no.6
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• pp.15-21
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• 1999

Carbon fibers were coated with carboxy modified poly(hydroxy ether)(C-PHE, water dispersed), water soluble polymers poly(hydroxy ether ethanol amine)(PHEA) or water insoluble poly(hydroxy ether)(PHE). Interfacial shear strength of polymer coated carbon fibers was measured by micro-droplet tests with vinyl ester resin, and approximately 30 samples were tested. The interfacial adhesion of poly-mers to carbon fibers was also evaluated, and diffusion behavior of polymer films in vinyl ester resin was investigated. The carbon fibers after testing and diffusion samples were analysed by SEM in order to understand adhesion mechanism. Interfacial shear strength of carbon fibers was enhanced by the coating of PHE and C-PHE which have good or marginal solubility in vinyl ester resin, respectively, but not by the coating of PHEA possibly due to the poor solubility in vinyl ester resin.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.4
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• pp.350-356
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• 2005

We report the space charge and the surface potential of the interface between metal and copper(Ⅱ)-phthalocyanine(CuPc) thin films by measuring the microwave reflection coefficients S/sub 11/ of thin films using a near-field scanning microwave microscope(NSMM). CuPc thin films were prepared on Au and Al thin films using a thermal evaporation method. Two kinds of CuPc thin films were prepared by different substrate heating conditions; one was deposited on preheated substrate at 150。C and the other was annealed after deposition. The microwave reflection coefficients S/sub 11/ of CuPc thin films were changed by the dependence on grain alignment due to heat treatment conditions and depended on thickness of CuPc thin films. Electrical conductivity of interface between metal and organic CuPc was changed by the space charge of the interface. By comparing reflection coefficient S/sub 11/ we observed the electrical conductivity changes of CuPc thin films by the changes of surface potential and space charge at the interface.

• Korean Journal of Materials Research
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• v.17 no.5
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• pp.263-267
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• 2007

Hafnium oxide $(HfO_2)$ films were deposited on Si(100) substrates by remote plasma-enhanced atomic layer deposition (PEALD) method at $250^{\circ}C$ using TEMAH [tetrakis(ethylmethylamino)hafnium] and $O_2$ plasma. $(HfO_2)$ films showed a relatively low carbon contamination of about 3 at %. As-deposited and annealed $(HfO_2)$ films showed amorphous and randomly oriented polycrystalline structure. respectively. The interfacial layer of $(HfO_2)$ films deposited using remote PEALD was Hf silicate and its thickness increased with increasing annealing temperature. The hysteresis of $(HfO_2)$ films became lower and the flat band voltages shifted towards the positive direction after annealing. Post-annealing process significantly changed the physical, chemical, and electrical properties of $(HfO_2)$ films. $(HfO_2)$ films deposited by remote PEALD using TEMAH and $O_2$ plasma showed generally improved film qualities compare to those of the films deposited by conventional ALD.

• Fibers and Polymers
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• v.2 no.2
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• pp.58-63
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• 2001

Silk fibroin (SF) was dissolved in calcium chloride/ethanol/water mixture(1/2/8 in mole ratio) at $70^{\circ}C$ for 4h. The dissolved silk fibroin was regenerated by casting the dialyzed solution into films. The films were treated with 50% aqueous solution of methanol for different times, and their antithrombogenicity was evaluated by in vivo tests. In vivo blood tests were made by a method of peripheral vein indwelling suture. It was found that the silk fibroin had a good antithrombogenicity and an absorbability even though the polymer showed foreign body reaction. Finally, the blood compatibilty of silk fibroin films which were subjected to structural change by the methoanl treatment, was examined in connection with their interfacial surface energy, and a correlation between these properties was found to be present.