• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.2
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• pp.83-86
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• 2013

The optical properties of ZnO thin film have been studied using photoluminescence(PL) spectroscopy with the change of sample temperatures from 10 K to 290 K. The spectrum at 10 K showed the characteristic emission lines of ZnO which were as follows: free exciton(FX) at 3.369 eV, neutral donor-bound exciton($D^0X$) at 3.360 eV, two electron satellite(TES) at 3.332 eV, $D^0X$-1LO at 3.289 eV, and donor-acceptor pair(DAP) transiton at 3.217 eV. From the spectral evolution with temperatures, two features could be identified as temperature went higher: (1) the bound excitons changed gradually into free excitons, (2) DAP turned into free electron-acceptor transition(e,$A^0$). The PL intensity of free exciton increased with the increase of temperatures, which was accompanied by the decrease of the intensity of bound excitions and bound excition-related transitons such as TES and $D^0X$-1LO. At 80 K DAP transition disappeared, while (e,$A^0$) transition started to appear at 30 K.

• Transactions on Electrical and Electronic Materials
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• v.1 no.3
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• pp.6-9
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• 2000

Selectively excited photoluminescence(PL) spectroscopy has been carried out on the ~1540 nm $^{4}$I$_{13}$ 3/ to $^{4}$I/wub 15/2/ emissions of the multiple Er$^{3+}$ centers observed in Er-implante undoped and Mg-doped GAN at temperatures ranging from 6K to 295K. The temperature dependence of the Er$^{3+}$ PL spectra selectively excited by below -gap light demonstrates different quenching rates for the distinct Er$^{3+}$ centers, and indicates that the PL spectra with the most rapid thermal quenching rats do not contribute to the room temperature, above-p-pumped Er$^{3+}$ spectrum. In addition, selective PL spectroscopy has ben carried out on the Er$^{3+}$ emission in Er-implanted undoped and Mg-doped GaN at temperatures ranging 6K to 295K. The results indicate that the previously reported enhancement of the violet-pumped centers contribution to the low temperature above excited Er$^{3+}$ PL in Mg-doped GaN is also evident at room temperature.temperature.

• Journal of the Korean Ceramic Society
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• v.44 no.5 s.300
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• pp.155-159
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• 2007

Blue light-emitting phosphors having the excitation spectrum range of the medium-long ultraviolet ($280nm{\sim}400nm$) have been prepared by solid state reaction method. As a starting material the natural alkaline feldspar powder produced from the domestic mine field in Buyeo, Chungnam-do. The photoluminescence characteristics and crystal structures have been analyzed for the phosphor samples. The powder mixture of the natural alkaline feldspar and the rare-earth oxide was calcined at $800{\sim}1000^{\circ}C\;for\;3{\sim}4h$ in air. The calcined samples we fully ground at room temperature and then heat-treated in the mild reducing gas atmosphere of $5%H_2-95%N_2$ mixture at $1100{\sim}1150^{\circ}C\;for\;3{\sim}4h$. The natural alkaline feldspar material consists of the monoclinic orthoclase ($KAlSi_3O_8$) and the triclinic albite ($NaAlSi_3O_8$) phases. At the $0.5wt%Eu_2O_3$ addition the PL spectrum showed the maximum intensity and with further increase of $Eu_2O_3$ the PL intensity decreased. The albite phase disappeared in the $Eu_2O_3$ doped phosphors. The effect of the co-doped activator on the PL characteristics have been also discussed.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.348-352
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• 2011

In this research, we have synthesized new pendant-type polyurethane polymers by introducing various chromophores with stilbene derivatives in the side-chain of the polymer backbone. The Stilbene monomers, N,N-bis(2-hydroxyethyl) amino-4'-cyanostilbene, N,N-bis(2-hydroxyethyl)amino-4'-methoxy stilbene, N,N-bis(2-hydroxyethyl)amino-4'-acetylstilbene, and N,N-bis(2-hydroxyethyl) amino stilbene, were synthesized by Wittig reaction. Another stilbene monomer, N,N-bis(2-hydroxyethyl)amino-4'-nitrostilbene, was synthesized by Knoevenagel condensation. By the measurement of UV-Vis absorption and Photoluminescence (PL) spectrum, we found that introduction of the electron-withdrawing group as a substituent shifts both UV-Vis and PL spectra to longer wavelength, and the introduction of the electron-donating group results in blue-shift of the spectrum. In case of polymer with $NO_2$ group as a substituent, PL is quenched.

• Journal of the Korean Ceramic Society
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• v.35 no.2
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• pp.145-150
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• 1998

ZnGa2O4 thin film phosphors were deposited on Si(100) (111) wafers by rf magnetron sputtering. The ef-fects of substrates and deposition parameters on the growing mechanisms were studied. As a results of the effect of substrate temperature tranistions of growth orientation and different growing behaviors were ob-served. Also polycrystalline ZnGa2O4 thin film could not be achieved without oxygen gas. PL spectrum of ZnGa2O4 thin films were analyzed and showed broad band luminescence spectrum.

• Korean Journal of Materials Research
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• v.15 no.7
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• pp.448-452
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• 2005

This study was based on organic electroluminescence display. Especially, TPD and $\alpha-NPD$ for the hole transport materials were synthesized by Ullmann reaction. This reaction was conducted between 3­methylphenylamine, 1-naphthylamine and 4,4'-diiodobiphenyl in toluene containing CuCl catalyst and KOH base. The structural property of reaction products were analyzed by FT-IR, $^1H-NMR$ spectroscopy, and thermal stability, reactivity and PL property were analyzed by melting point, yield and emission spectrum, respectively. The photoluminescence spectra of a pure TPD and $\alpha-NPD$ were observed at approximately 416nm and 438nm respectively. In this study, it was known that the melting point, yield, PL properties of TPD and $\alpha-NPD$ were changed by substituent group of amines.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1491-1504
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• 2012

InP quantum dot (QD)-organosilicon nanocomposites were synthesized and their photoluminescence quenching was mainly investigated because of their applicability to white LEDs (light emitting diodes). The as-synthesized InP QDs are capped with myristic acid (MA), which are incompatible with typical silicone encapsulants. We have introduced a new ligand, 3-aminopropyldimethylsilane (APDMS), which enables embedding the QDs into vinyl-functionalized silicones through direct chemical bonding. The exchange of ligand from MA to APDMS does not significantly affect the UV absorbance of the InP QDs, but quenches the PL to about 10% of its original value with the relative increase in surface related emission intensities, which is explained by stronger coordination of the APDMS ligands to the surface indium atoms. InP QD-organosilicon nanocomposites were synthesized by connecting the QDs using a short cross-linker such as 1,4-divinyltetramethylsilylethane (DVMSE) by the hydrosilylation reaction. The formation and changes in the optical properties of the InP QD-organosilicon nanocomposite were monitored by ultraviolet visible (UV-vis) absorbance and steady state photoluminescence (PL) spectroscopies. As the hydrosilylation reaction proceeds, the QD-organosilicon nanocomposite is formed and grows in size, causing an increase in the UV-vis absorbance due to the scattering effect. At the same time, the PL spectrum is red-shifted and, very interestingly, the PL is quenched gradually. Three PL quenching mechanisms are regarded as strong candidates for the PL quenching of the QD nanocomposites, namely the scattering effect, F$\ddot{o}$rster resonance energy transfer (FRET) and cross-linker tension preventing the QD's surface relaxation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.12
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• pp.992-995
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• 2011

The optical properties of ZnO thin film, being treated by O-plasma, have been studied using Photoluminescence(PL) spectroscopy with the change of temperature from 10 K to 290 K. Two characteristic peaks were identified at 10 K : 3.357 eV($D^{\circ}X$) and 3.324 eV(TES). The peak of $D^{\circ}X$ is believed to be due to neutral donor bound excitons where the donor is in the ground state. However, the TES(Two Electron Satellite) peak indicates the excited state of the donor(excitation energy was ~30 meV). The donor binding energy was estimated to be 44 meV, which indicates the possible presence of the neutral donor bound excitons at RT. The thermal effect including thermal broadening was identified from temperature evolution of the spectrum. Both the peak intensity and the peak energy have decreased as the temperature increases. As the temperature approaches to RT, the two peak merges into one broad peak, which is considered a combination of multiple peaks having different physical origins.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.6
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• pp.279-283
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• 2003

In this study, ZnTe : S single crystal thin films substituted by sulfur were grown on GaAs (100) substrates by hot-wall epitaxy. The photoluminescence (PL) characteristics of ZnTe : S single crystal thin films was measured to investigate the effects due to sulfur atoms in the ZnTe layer. The Peak of 2.339 eV identified as the isoelectronic center was observed in low temperature PL spectrum, but PL spectra which the origin had not been well-explained were not observed. Temperature dependence of PL intensities of the light hole free exciton was explained by extrinsic self-trapping. Besides it is reported that the emission lines near absorption edge at room temperature were observed.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.191-191
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• 2012

InP quantum dot (QD) - organosilicon nanocomposites were synthesized and their photoluminescence quenching was mainly investigated because of their applicability to white LEDs (light emitting diodes). The as-synthesized InP QDs which were capped with myristic acid (MA) were incompatible with typical silicone encapsulants. Post ligand exchange the MA with a new ligand, 3-aminopropyldimethylsilane (APDMS), resulted in soluble InP QDs bearing Si-H groups on their surface (InP-APDMS) which allow embedding the QDs into vinyl-functionalized silicones through direct chemical bonding, overcoming the phase separation problem. However, the ligand exchange from MA to APDMS caused a significant decrease in the photoluminescent efficiency which is interpreted by ligand induced surface corrosion relying on theoretical calculations. The InP-APDMS QDs were cross-linked by 1,4-divinyltetramethylsilylethane (DVMSE) molecules via hydrosilylation reaction. As the InP-organosilicon nanocomposite grew, its UV-vis absorbance was increased and at the same time, the PL spectrum was red-shifted and, very interestingly, the PL was quenched gradually. Three PL quenching mechanisms are regarded as strong candidates for the PL quenching of the QD nano-composites, namely the scattering effect, Forster resonance energy transfer (FRET) and cross-linker tension preventing the QD's surface relaxation.