• 한국세라믹학회지
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• 제35권6호
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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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• 제18권2호
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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.

• 한국재료학회지
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• 제28권6호
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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.

• 한국표면공학회지
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• 제48권5호
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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 ${\approx}530nm$.

• 한국재료학회지
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• 제15권5호
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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.

• 한국전기전자재료학회논문지
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• 제20권8호
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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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• 제7권2호
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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.

• 한국광학회:학술대회논문집
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• 한국광학회 2007년도 하계학술발표회 논문집
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• pp.103-103
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• 2007

• Journal of Radiation Protection and Research
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• 제36권3호
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• pp.160-167
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• 2011

본 연구는 두경부 방사선치료에서 산란판(beam spoiler)과 볼루스(bolus)를 사용함에 따라 깊이가 다른 원발종양과 림프절 전이성 종양의 선량 변화를 이온함과 광자극발광선량계(optically stimulated luminescence detectors. OSLDs)를 이용하여 치료계획검증 방법으로 교차 비교하였다. 치료계획검증은 치료계획시스템에서 얻은 동일 조사 조건을 검출기가 삽입 가능한 고체 팬텀에 모사하는 방법으로 산란판과 0.5, 1 cm 볼루스를 비교하였으며 두 선량계의 교차비교는 측정 오차가 ${\pm}$2% 미만일 때 신뢰성이 있다고 판단하였다. 연구 결과 0.5 cm 두께의 산란판과 피부간 거리가 10 cm 일 때 최적의 선량분포를 얻을 수 있었으며 볼루스에 비하여 피부선량이 작고 중심부 원발종양 선량의 감소가 작았다. 또한 두 선량계의 교차 비교는 ${\pm}$1% 이내로 유의한 결과를 보였다. 두경부 종양의 방사선치료시 산란판을 사용함으로써 피부 부작용을 줄이면서 종양에 최적의 선량분포를 달성할 수 있다고 판단되었으며 향후 임상에 적용하기 위한 연구가 시행되어야 할 것이다.

• 한국재료학회지
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• 제25권9호
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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 $Er^{3+}$.