• Journal of the Korean Ceramic Society
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• v.35 no.6
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• pp.619-625
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• 1998

Mn doped {{{{ {Zn {Ga }_{2 }O }_{4 } }} thin film phosphors were prepared on Si(100) wafers and ITO coated glass substrates by rf magnetron sputtering technique and the effects of the substrates dopant and the sputtering paramet-ers were analyzed, Changes of the oreintation were observed after annealine tratment. The grain size of {{{{ {Zn {Ga }_{2 }O }_{4 } }} : Mn thin film deposited on Si wafer was smaller than that on ITO/glass substrate which resulted in higher PL intensity. The PL spectra of Mn doped {{{{ {Zn {Ga }_{2 }O }_{4 } }} thin films showed sharp green luminescence spec-trum. According to CL spectrum it could be concluded that Mn ions acted as an actuator for green emission by substituting Zn atom sites.

• Bulletin of the Korean Chemical Society
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• v.18 no.2
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• pp.185-189
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• 1997

The effect of pH and sodium dodecyl sulfate (SDS) micelle on the quenching of Ru(bpy)32+ luminescence by N-alkyl-4,4'-bipyridinium ions (RBPY+: R=methyl, octyl, dodecyl, benzyl) were investigated. In the absence of SDS, the quenching rate at pH 2 is similar to that of the corresponding methylalkyl viologens and much greater than that in pH 8 solution due to greater reducibility of the protonated form of RBPY+ (HRBPY2+). The quenching rate at pH 2 is strongly enhanced by the presence of SDS, while that at basic pH is greatly retarded. These observations are explained by deep embedment of RBPY+ into the hydrophobic hydrocarbon region of the micelle, whereas Ru(bpy)32+ and HRBPY2+ locate in the Stern layer of the micelle.

• Korean Journal of Materials Research
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• v.28 no.6
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• pp.355-360
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• 2018

$LuNbO_4:0.2Yb^{3+},xTm^{3+}$ powders were prepared using a solid-state reaction process. The effects of the amount of Tm on up-conversion(UC) and down-conversion(DC) luminescence properties are investigated. X-ray diffraction patterns confirm that $Yb^{3+}$ and $Tm^{3+}$ ions are successfully incorporated into Lu sites. Under 980 nm excitation, the UC spectra of the powders predominantly exhibit strong near-infrared emission bands that peak at 805 nm, whereas weak 480 nm emission bands are observed as well. The emission bands are assigned to the $^1G_4{\rightarrow}^3H_6$ (480 nm) and 3 $^3H_4{\rightarrow}^3H_6$ (805 nm) transitions of the $Tm^{3+}$ ions via an energy transfer from $Yb^{3+}$ to $Tm^{3+}$; two- and three-photon UC processes are responsible for the 805 and 480 nm emissions, respectively. The DC emission spectra exhibit blue emission ($^1D_2{\rightarrow}^3F_4$) of $Tm^{3+}$ at 458 nm. The amount of Tm affects the emission intensity with the strongest emissions at x = 0.007 and 0.02 for the UC and DC luminescence, respectively. The results demonstrate that $LuNbO_4:Yb^{3+},Tm^{3+}$ phosphors are suitable for bio-applications.

• Journal of the Korean institute of surface engineering
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• v.48 no.5
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• pp.211-217
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• 2015

To fabricate white LED having a high color rendering index value, red color phosphor mixed with the green color phosphor together in the blue chip, namely the blue chips with RG phosphors packaging is most favorable for high power white LEDs. In our previous papers, we reported on successful syntheses of $Sr_{2-}$ $Si_5N_8:Eu^{2+}$ and $CaAlSiN_3$ phosphors for red phosphor. In this work, for high power green phosphor, greenemitting ternary nitride $Ba_3Si_6O_{12}N_2:Eu^{2+}$ phosphor was synthesized in a high frequency induction furnace under $N_2$ gas atmosphere at temperatures up to $1400^{\circ}C$ using $EuF_3$ as a raw material for $Eu^{2+}$ dopant. The effects of molar ratio of component and experimental conditions on luminescence property of prepared phosphors have been investigated. The structure and luminescence properties of prepared $Ba_3Si_6O_{12}N_2:Eu^{2+}$ phosphors were investigated by XRD and photoluminescence spectroscopy. The excitation spectra of $Ba_3Si_6O_{12}N_2:Eu^{2+}$ phosphors indicated broad excitation wavelength range of 250 - 500 nm, namely from UV to blue region with distinct enhanced emission spectrum peaking at ${\approx}530nm$.

• Korean Journal of Materials Research
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• v.15 no.5
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• pp.323-333
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• 2005

Effects of gases to growth of $SiO_2$ nanowires were characterized. $N_2$, Ar, and $O_2$ gas's effect were determined. $SiO_2$ nanowires growth scheme was varied by kind and flow rates of gases because of amounts of $O_2$. Flow rates of gases and kind of substrates affected nanowires' diameters, lengths and morphologies of grown nano wires. With increasing flow rates of gases, nanowire's diameter increased because of additional VS and SLS reactions. By TEM characterization, We knows that, grown $SiO_2$ nanowires on Si substrate showed two shell structures. These shapes of nanowires were formed by reaction of additional SLS growth. Grown $SiO_2$ nanowires showed blue luminescence by PL characterization These Blue luminescence was due to quantum confinement effect and oxygen vacancies in the nanowires.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.8
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• pp.716-719
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• 2007

The effects of the evaporation rate of MgO films using an electron beam on the MgO properties and the discharge characteristics of a plasma display panel (PDP) were investigated and analyzed. MgO films were deposited with the various MgO evaporation rates. The MgO properties such as the crystal orientation, the surface roughness, and the film structure were inspected using XRD (X-ray diffraction), AFM (atomic force microscopy). From the experiments and Paschen law, the maximum value of the secondary electron emission coefficient $({\gamma})$ was obtained at the evaporation rate of $5{\AA}/sec$. The XRD results and cathode-luminescence (CL) spectra show the ${\gamma}$ values are correlated with F/F+ centers of the molecular structure of MgO films. The minimum firing voltage and the maximum luminous efficiency were obtained at an evaporation rate of $5{\AA}/sec$. In the MgO film deposited at $5{\AA}/sec$, the (200) orientation and F+ center were most intensive.

• Journal of Information Display
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• v.7 no.2
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• pp.1-5
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• 2006

The characteristics of MgO layer deposited under hydrogen atmosphere were investigated. Hydrogen gas was introduced during e-beam evaporation coating process of MgO layer and its effects on microstructure, cathode luminescence spectra, discharge voltages and effective yield of secondary electron emission were examined. The results indicated that the hydrogen influences the concentration and energy levels of defects in MgO layer, which in turn affects the luminance efficiency and discharge delays of the panels significantly.

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.103-103
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• 2007

• Journal of Radiation Protection and Research
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• v.36 no.3
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• pp.160-167
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• 2011

This study conducts cross-comparison through verification of treatment planning of using beam spoiler and bolus, according to the dose variation of different tumor bed and metastatic lymph node cancers, against ionization and optically stimulated luminescence detectors(OSLDs), in head and neck radiotherapy. Verification of treatment planning examined the feasibility of inserting detectors through simulated solid dry water slabs under identical irradiated conditions from treatment planning system to measure beam spoiler and 0.5, 1 cm bolus. In addition, two detectors were cross-compared for verification of treatment planning accuracy and reliability within ${\pm}$2%. The study found that, given a beam spoiler thickness of 0.5 cm and beam spoiler-to-skin distance of 10 cm subjected to optimal dose distribution given for metastatic lymph node cancers, the bolus low-level skin dose was less, and the tumor bed dose reduced slightly. Additionally, two detectors were cross-compared for accuracy within ${\pm}$1%. Accordingly, The use of beam spoiler was determined that reduces skin side effects and can deliver an optimal dose distribution for tumor, and to apply to future clinical studies should be performed.

• Korean Journal of Materials Research
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• v.25 no.9
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• pp.475-479
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• 2015

$YNbO_4:Yb^{3+}/Er^{3+}$ is synthesized using a solid-state reaction process with a LiCl flux. The effects of the Er/(Yb+Er) ratios ($R_{Er}$) on the up-conversion (UC) and down-conversion (DC) spectra are investigated. The XRD data confirm that the $Yb^{3+}$ and $Er^{3+}$ ions are fully substituted for the $Y^{3+}$ sites. The UC emission spectra activated by 980 nm consists of green and red emission bands, which originate from the $Er^{3+}$ ions through an energy transfer (ET) process from $Yb^{3+}$ to $Er^{3+}$. The UC emission intensity depends on the $R_{Er}$ value, and the findings demonstrate that $R_{Er}{\leq}0.14$ is suitable for an effective UC process. The DC emission spectra under 269 nm radiation of the synthesized powders exhibits not only a strong blue emission assigned to the $[NbO_4]^{3-}$ niobates, but also green peaks that originate from the $Er^{3+}$ ions through an ET process between $[NbO_4]^{3-}$ and $Er^{3+}$.