• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.4
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• pp.145-151
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• 2005

Color enhancement of African rubies with dark red was carried out by the heat treatment and the hydrothermal treatment method respectively. The heat treatment method brought about an adverse effect causing the color to be deteriorated. However, the hydrothermal treatment method enhanced its color and clarity. The hydrothermal treatment conditions for color enhancement of them were as follows: solvent: 0.9M $Na_2CO_3-1M\;K_2CO_3$, temperature: $450^{\circ}C$, duration: 48 hrs, filling: $30\%$, pressure: 375 atm. As the results of characteristics for African rubies obtained under these conditions, it was known that the amount of $Cr^{3+},\;Fe^{3+},\;Ti^{4+}$ was reduced after the hydrothermal treatment from the ICP/MS and XRF analyses. Also, it was found that the red color from the colorimeter analyses was getting lighter. These results were consistent with the PL analysis showing that the intensity of the luminescence peak generated by the electron transition of $Cr^{3+}$ ion became lower after the hydrothermal treatment compared with the non-treated rubies.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.370-373
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• 2003

A search for a new phosphor composition of excellent performance in systematic ways requires lots of research efforts, and often turns out to be very timeconsuming and difficult. Thus, usually practical ways are taken to improve the performance of phosphors. A few examples of practical surface treatments on phosphors such as $In_2O_3$ coating on $ZnGa_2O_4:Mn$, phosphoric acid treatment on ZnS:Ag,Cl, and base KOH treatment with ultrasonication on ZnS:Ag,Cl are presented. The reasons for the improvement of luminescence intensity or degradation properties after these treatments are discussed based upon careful analyses on the surface of the phosphors and a proposed model on charge carriers generated by electron beam excitation.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.243-252
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• 2002

We propose a new concept: that of photonic crystal phosphors (PCPs) for display and phosphor related applications. It is well known that microcavities with dimensions comparable to the emitting wavelength strongly enhance light-matter interactions, resulting in a significant increase in spontaneous emission rate, which can be directly translated into enhancement in phosphor efficiency. In recent simulations we have demonstrated that when a microcavity is formed in a nano-phosphor structure, the luminescence band is modified, and can be made spectrally sharp and tunable by engineering the geometry/material properties of the cavity and the surrounding photonic crystal lattice. New phosphor material structures based on photonic crystals are proposed. Applications to thin film EL phosphors and particle phosphors are discussed. Additionally, economic methods of synthesizing and incorporating PCPs into current display applications are proposed.

• Journal of Integrative Natural Science
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• v.1 no.1
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• pp.32-35
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• 2008

We fabricated surface pattern on a light guide panel (LGP) using $CO_2$ laser to improve the luminescence performance of inner-scatterer LGP, which is made of PMMA sample with exploiting Q-switched $2^{nd}$ harmonic Nd:YAG laser engraving system, and the effect of surface pattern in the brightness distribution of LGP was analysed. To prove the feasibility of proposed method in the enhancement of LGP performance, we designed three different surface patterns on the inner-scatterer LGP. The experimental results has proved the potential in the application of surface pattern to increasing the brightness of inner-scatterer LGP.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.444-445
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• 2007

Aluminum-doped zinc oxide (AZO) films are attractive materials as transparent conductive electrode because they are inexpensive, nontoxic and abundant element compared with indium tin oxide (ITO). AZO films have been deposited on glass (coming 1737) substrates by RF magnetron sputtering system. An ultrathin layer of nickel oxide (NiO) was deposited on the AZO anode to enhance the hole injections in organic light-emitting diodes (OLED). The current density-voltage and luminescence-voltage properties of devices were studied and compared with ITO device.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.09a
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• pp.35-39
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• 2005

Phosphor powders of zinc gal late added with Mg and rare-earth elements were prepared by sol id state reaction to improve luminescent properties. Green emitting $ZnMnGa_{2}O_{4}$ reached maximum intensity at Mn=0,005 mole$\%$ and further improvement was achieved by addition of $Mg^{2+}$. Tm, Mg-added zinc gallate phosphor exhibited a strong blue band emission, peaking at about 420 nm with the maximum intensity at the concentration of 0.003 mole$\%$ Mg and 0.015 mole$\%$ Tm. Deepening of the potential wells of the ground and excited states was suggested to be the cause for the enhancement in emission intensity at optimal doping of Mg and Tm.

• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.189-192
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• 2012

Manufacturing process for silicate glass phosphors containing Eu2+ activator and their photoluminescence property have been studied. We adopted powder sintering process instead of traditional glass melting process for making glass phosphor. At first, phosphor powders were synthesized at 1200 ℃ for 2-3 hours under a reducing atmosphere with 10% H2-90% N2 gas mixture. The reduced powders were compacted into discs and then the discs weresintered at 1400 ~ 1500 ℃ for 1 hr under a reducing atmosphere of 5H2-95% N2. The enhancement of PL intensity by Al2O3 addition, XPS binding energy shift of Si 2p and O 1s, sintering shrinkage, and crystallization were characterized.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.141-141
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• 2010

The effect of thermal anneal on the characteristics of structural properties and the enhancement of luminescence and photovoltaic (PV) characteristics of silicon-rich silicon-nitride films were investigated. By using an ultra high vacuum ion beam sputtering deposition, B-doped silicon-rich silicon-nitride (SRSN) thin films, with excess silicon content of 15 at. %, on P-doped (n-type) Si substrate was fabricated, sputtering a highly B doped Si wafer with a BN chip by N plasma. In order to examine the influence of thermal anneal, films were then annealed at different temperature up to $1100^{\circ}C$ under $N_2$ environment. Raman, X-ray diffraction, and X-ray photoemission spectroscopy did not show any reliable evidence of amorphous or crystalline Si clusters allowing us concluding that nearly no Si nano-cluster could be formed through the precipitation of excess Si from SRSN matrix during thermal anneal. Instead, results of Fourier transform infrared and X-ray photoemission spectroscopy clearly indicated that defective, amorphous Si-N matrix of films was changed to be well-ordered thanks to high temperature anneal. The measurement of spectral ellipsometry in UV-visible range was carried out and we found that the optical absorption edge of film was shifted to higher energy as the anneal temperature increased as the results of thermal anneal induced formation of $Si_3N_4$-like matrix. These are consistent with the observation that higher visible photoluminescence, which is likely due to the presence of Si-N bonds, from anneals at higher temperature. Based on these films, PV cells were fabricated by the formation of front/back metal electrodes. For all cells, typical I-V characteristic of p-n diode junction was observed. We also tried to measure PV properties using a solar-simulator and confirmed successful operation of PV devices. Carrier transport mechanism depending on anneal temperature and the implication of PV cells based on SRSN films were also discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.420.2-420.2
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• 2016

Various fields have been paid attention to upconversion nanoparticles (UCNPs) because of its unique optical properties. Moreover, to use the UC luminescent techniques through cell images for identified apoptosis/necrosis of cancer cells have been performed. They have been studied for a versatile biomedical application such as a biosensing tool, or delivery of active forms of medicines inside living cells. UCNPs have distinctive characteristics such as photoluminescence, special emission, low background fluorescence signal and good colloidal stability, which have many advantages compared with the organic dyes and quantum dots. UCNPs have not only a great potential for imaging (UC luminescence) but also therapies (photo-thermal therapy, PTT and photo-dynamic therapy, PDT) in cancer diagnostics. Therefore, we report the enhancement of upconversion red emission in NaYF4:Yb3+,Er3+ nanoparticles, synthesized via solid-state method with the thermal decomposition of trifluoroacetate as precursors and organic solvent at a high boiling point. The UCNPs have an emission in the field of near infrared wavelength, cubic shape and nano-size in length. In this study, we will further investigate it for cancer therapy with NIR optical detection onto the solid substrate.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.9
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• pp.812-815
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• 2003

In this study, the MgO thin-film passivation layer was adopted to protect passive matrix organic light emitting diode(PMOLED) with the cathode separator from moisture and oxygen. Using the substrate rotate and tilt technique during the deposition, the organic and cathode layers were perfectly covered with MgO. And then, we analyzed the difference of the current-voltage and luminescence characteristics between passivated OLED of the MgO and non-passivated OLED. It was found that the number of dark spot generated from the degradated pixel was decreased owing to the Mgo thin-film passivation layer using the tilt ＆ rotate technique. And the half-life time passivated OLED was improved two times more. Thus, the MgO could be vaccum-deposited under the low temperature and had a merit that the organic layer was not much affected. We can consider that MgO thin film passivation method can be adopted to protect the OLED from moisture and oxygen and can offer the enhancement of lifetime.