• Proceedings of the Korean Magnestics Society Conference
• /
• 2008.12a
• /
• pp.265.2-265.2
• /
• 2008

• Proceedings of the Korean Magnestics Society Conference
• /
• 2008.12a
• /
• pp.81.1-81.1
• /
• 2008

• Journal of the Korean Mathematical Society
• /
• v.43 no.4
• /
• pp.691-701
• /
• 2006

In this paper, we construct a new exotic smooth 4-manifold X which is homeomorphic, but not diffeomorphic, to ${\mathbb{C}}\mathbb{P}^2{\sharp}13\overline{\mathbb{C}\mathbb{P}}^2$. Moreover the manifold X has vanishing Seiberg-Witten invariants for all $Spin^c$-structures of X and has no symplectic structure.

• Journal of the Microelectronics and Packaging Society
• /
• v.10 no.4
• /
• pp.35-38
• /
• 2003

Polymer light emitting diode (PLED) with an ITO/MEH-PPV/Al structure were prepared by spin coating method on the ITO (indium tin oxide)/glass substrates, using poly(2-methoxy-5-(2-ethylhexoxy)-1,4-phenylenevinylene (MEH-PPV) as the light emitting material. The dependence of heat treatment on the electrical and optical properties for the prepared PLED samples were investigated. The luminance decreased greatly from 630 cd/$\m^2$ to 280 cd/$\m^2$ at 10V input voltage as the heating temperature increased from $65^{\circ}C$ to $170^{\circ}C$. In addition, the luminance efficiency was found to be about 2 lm/W for the sample heat treated at $65^{\circ}C$. These results may be related to the interface roughness and/or the formation of an insulation layer, which is caused by the reaction between electrode and MEH-PPV organic luminescent film layer.

• Journal of the Korean Magnetics Society
• /
• v.11 no.6
• /
• pp.272-277
• /
• 2001

A spin valve structure of Ta/NiFe/CoFe/Cu/CoFe/Ru/CoFe/FeMn/Ta which has a synthetic antiferromagnet (CoFe/Ru/CoFe), was fabricated by using a magnetron sputtering system. The thickness and composition of magnetic free and pinned layers affect the magnetic properties such as exchange interaction strength of each layer and so on. Even though Rutherford Backscattering Spectrometry (RBS) has advantages of quantitative and non-destructive analysis, it is almost impossible to determine the thickness and composition of magnetic thin films using lBS because of its poor mass resolution for a higher atom number (Z>20). In this study, quantitative analysis of the element composition and thickness for the spin valve sample was performed by combining both Proton Induced X-ray Emission Spectrometry (PIXE), which is one of element specific analysis techniques, and grazing-exit RBS with a highly improved depth resolution and absolute quantitative analysis. For the quantitative analysis, standardization of PIXE was carried out with NiFe, CoFe, and FeMn layers, which are one of constituent layers of spin valve films. Through PIXE standardization and the aid of PHE experimental results of the spin valve sample, ire overlapped signal in a grazing-exit RBS spectrum were successfully resolved and the thickness of the Ru layer was determined with a resolution of ∼1 .

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.3 no.3
• /
• pp.161-165
• /
• 2002

Ge-doped rnulticomponent oxide glasses were prepared by a conventional melting method. The change of micro structure in glasses was investigated by using PL (photoluminescence) and ESR (electron spin resonance). Before UV irradiation, the PL intensity increased according to germanium contents, but decreased the intensity as soon as UV irradiation. A changed property was recovered near it original properties when it was annealed. These photodarkening and thermal bleaching effect were observed by ESR intrument. These effect did not change the glass phase but vary only change of micro structure.

• Journal of the Optical Society of Korea
• /
• v.18 no.1
• /
• pp.45-49
• /
• 2014

Well-crystallized $BaSi_2O_5:Eu^{2+}$ phosphor films were synthesized by heat treatment of spin-coated BaO:Eu on $SiO_2$ glass. We investigated luminescence-structure properties of these phosphor films as a function of heat-treatment temperature. From x-ray diffraction patterns, our $BaSi_2O_5:Eu^{2+}$ phosphor films revealed that (111)- and (204)-crystal planes of $BaSi_2O_5$ crystal were dominantly increased with an increase of heat-treatment temperature. Photoluminescence intensities of $BaSi_2O_5:Eu^{2+}$ phosphor films were increased with amount of these crystal planes. It can be explained that $Eu^{2+}$ ions were stably occupied at specific crystal orientation of $BaSi_2O_5$ crystal, enhancing the luminescent intensities of $BaSi_2O_5:Eu^{2+}$ phosphor films. In addition, our $BaSi_2O_5:Eu^{2+}$ phosphor films had transmittance of 70% at 510 nm,.due to the dense morphology and specific crystallinity of $BaSi_2O_5:Eu^{2+}$ phosphor films.

• Macromolecular Research
• /
• v.16 no.8
• /
• pp.725-733
• /
• 2008

Polyimide (PI) multilayer thin films were prepared by spin-coating from a poly(amic acid) (PAA) and poly(amic acid) ammonium salt (PAAS). PI was prepared from pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA) PAA. Different compositions of PAAS were prepared by incorporating triethylamine (TEA) into PMDA-ODA PAA in dimethylacetamide. PI multilayer thin films were spin-coated from PMDA-ODA PAA and PAAS. The PAAS comprising cationic and anionic moieties were spherical with a particle size of $20{\sim}40\;nm$. Some particles showed layers with ammonium salts, despite poor ordering. Too much salt obstructed the interaction between the polymer chains and caused phase separation. A small amount of salt did not affect the interactions of the interlayer structure but did interrupt the stacking between chains. Thermogravimetric analysis (TGA) showed that the average decomposition temperature of the thin films was $611^{\circ}C$. All the films showed almost single-step, thermal decomposition behavior. The nanostructure of the multilayer thin films was confirmed by X -ray reflectivity (XRR). The LF 43 film, which was prepared with a 4:3 molar ratio of PMDA and ODA, was comprised of uniformly spherical PAAS particles that influenced the nanostructure of the interlayer by increasing the interaction forces. This result was supported by the atomic force microscopy (AFM) data. It was concluded that the relationship between the uniformity of the PAAS particle shapes and the interaction between the layers affected the optical and thermal properties of PI layered films.

• Journal of the Korean Magnetics Society
• /
• v.8 no.5
• /
• pp.288-294
• /
• 1998

Effect of degree of intermixing at the Ta/NiFe interface induced by varying applied substrate bias voltage during NiFe free layer deposition on change of magnetoresistance in Substrate/Ta/NiFe/Cu/NiFe/FeMn/Ta spin valve multilayers was investigated. It was found that the optimum NiFe free layer thickness showing a maximum MR increase with increasing the bias voltage. The increase of the optimum thickness was due to the increase of the intermixed layer thickness with a bias voltage. The weak ferromagnetic or non ferromagnetic intermixed layer plays as a spin-independent scattering region and does not contribute on spin-dependent scattering. The existence of the intermixed layer was proved by the means of electrical resistivity and magnetization changes. In the present study, the optimum "effective" free layer thickness which gives the highest MR ratio was a constant independent of the magnitude of the bias voltage we have used.have used.

• Journal of the Korean Magnetic Resonance Society
• /
• v.9 no.2
• /
• pp.138-154
• /
• 2005

Vanadium-incorporated aluminophosphate molecular sieve $VO^{2+}-SAPO-5$ was studied by electron spin resonance (ESR) and electron spin echo modulation (ESEM) spectroscopies to determine the vanadium structure and interaction with various adsorbate molecules. It was found that the main species at low concentration of vanadium is a monomeric vanadium units in square pyramidal or distorted octahedral coordination, both in oxidation state (IV) for the calcined hydrated material and in oxidation state (V) for the calcined material. After calcinations in $O_2$ and exposure to moisture, only species A is observed with reduced intensities. It is suggested as a $VO(H_2O)_3^{2+}$ complex coordinated to two framework oxygen bonded aluminum. When calcined, hydrated $VO^{2+}-}SAPO-5$ is dehydrated at elevated temperature, a species loses its water ligands and transforms to $VO^{2+}$ ions coordinated to two framework oxygens (species B). Species B reduces its intensity, significantly after treatment with $O_2\;at\;600^{\circ}C$ for 5 h, thus suggesting oxidation of $V^{4+}\;to\;V^{5+}$. When dehydrated $VO^{2+}-SAPO-5$ contacts with $D_2O$ at room temperature, the EPR signal of species A is observed. Thus species assumed as a $VO^{2+}(O_f)_2(D_2O)_3$, by considering two framework oxygens. Adsorption of deuterated ethanol, propanol on dehydrated $VO^{2+}_{-}SAPO-5$ result in another new vanadium species E and F, respectively, which are identified as a $VO^{2+}-(CH_3CH_2OD)_3,\;VO^{2+}-(CH_3CH_2CH_2OD)_2$ complex. When deuterated benzene is adsorbed on dehydrated $VO^{2+}-SAPO-5$, another new vanadium species G, identified as a $VO^{2+}-(C_6D_6)$ is observed. Possible coordination geometries of these various complexes are discussed.