• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1096-1099
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• 2006

$II-III_2-(S,Se)_4$ structured of phosphor have been used at various field because those have high luminescent efficiency and broad emission band. Among these phosphors, europium doped $BaGa_2S_4$ was prepared by solid-state method and we try to look into an application possibility due to an emissive property of UV region. Also, general sulfide phosphors were synthesized by using injurious $H_2S\;CS_2$ gas. However, this study prepared $BaGa_2S_4:Eu^{2+}$ phosphor is addition to excess sulfur under 5% $H_2/95%\;N_2$ reduction atmosphere. So, this process could large scale synthesis because of non-harmfulness and simple process. The photo-luminescence efficiency of the prepared $BaGa_2S_4:Eu^{2+}$ phosphor increased 20% than commercial $SrGa_2S_4:Eu^{2+}$ phosphor. The prepared $BaGa_2S_4:Eu^{2+}$ could apply to green phosphor for white LED of three wavelengths.

• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.237-242
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• 2006

Nowadays, LEDs has been applied to the luminescent devices of various fields because of the invention of high efficient blue chip. Recently, especially, the white LEDs composed of InGaN blue chips and a yellow phosphor (YAG:Ce3+) have been investigated extensively. With the exception of YAG:Ce3+ phosphor, however, there are no reports on yellow phosphor that has significant emission in the 450~470 nm excitation range and this LED system is the rather low color rendering index due to their using two wavelength. Hence, we have attempted to synthesize thiogallate phosphors that efficiently under the long wavelength excitation range in the present case. Among those phosphors, we have synthesized Sr2Ga2S5:Eu2+ phosphor by change the host material of SrGa2S4:Eu2+ which is well known phosphor and we investigated the luminescent properties. In order to obtain the harmlessness and simplification of the synthesis process, sulfide materials and mixture gas of 5 % H2/95 % N2 were used instead of the CS2 or H2S gas. The prepared phosphor shows the yellow color peaking at the 550 nm wavelength and it possible to emit efficiently under the broad excitation band in the range of 300~500 nm. And this phosphor shows high luminescent intensity more than 110 % in comparison with commercial YAG:Ce3+ phosphor and it can be applied for UV LED due to excitation property in UV region.

• Korean Journal of Materials Research
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• v.12 no.9
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• pp.735-739
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• 2002

$(Y,Gd)BO_3$: Eu, $Zn_2$$SiO_4$ : Mn and $BaMgAl_{10}$ $O_{17}$ : Eu phosphors used in PDP were continuously irradiated by vacuum ultra violet generated from the penning gas (96%Ar+4%Xe) discharge and then the change of emitting intensity with time was investigated. The brightness of these phosphors decreased exponentially with VUV excitation time. The experimental data showed that the degradation rate increased in the order of $Zn_2$$SiO_4$ : Mn>(Y,Gd)$BO_3$: Eu>$BaMgAl_{10}$ $O_{17}$ : Eu phosphor. This different degradation property of phosphors was interpreted in terms of brightness saturation and stability against VUV irradiation. It was found that the degradation property of $(Y,Gd)BO_3$ : Eu red phosphor synthesized by ultrasonic thermal spray was superior to commercial phosphor.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.447-453
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• 2011

The monodisperse spherical $SiO_2$ particles were overcoated with $Y_2O_3:Eu^{3+}$ phosphor layers via a Pechini sol-gel process and the resulting $SiO_2@Y_2O_3:Eu^{3+}$ core-shell phosphors were subsequently annealed at $800^{\circ}C$ at an ambient atmosphere. The crystallographic structure, morphology, and luminescent property of core-shell structured $SiO_2@Y_2O_3:Eu^{3+}$ phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL). The spherical, nonagglomerated $SiO_2$ particles prepared by a Stober method exhibited a relatively narrow size distribution in the range of 260-300 nm. The thickness of phosphor shell layer in the core-shell particles can be facilely controlled by varying the coating number of $Y_2O_3:Eu^{3+}$ phosphors. The core-shell structured $SiO_2@Y_2O_3:Eu^{3+}$ phosphors showed a strong red emission, which was dominated by the $^5D_0-^7F_2$ transition (610 nm) of $Eu^{3+}$ ion under the ultraviolet excitation (263 nm). The PL emission properties of $SiO_2@Y_2O_3:Eu^{3+}$ phosphors were also compared with pure $Y_2O_3:Eu^{3+}$ nanophosphors.

• Journal of the Korean Vacuum Society
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• v.12 no.4
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• pp.275-280
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• 2003

Epitaxial Gd$_2O_3:Eu^{3+}$luminescent thin films have been grout on Si(III) substrates using ionized Cluster Beam Deposition (ICBD). After the film growing, they were implanted and post annealed to change the crystal structure. The initial growth stage was monitored by using in-situ Reflection High Energy Electron Diffraction (RHEED). The formed crystal structure was identified with X-ray diffraction (XRD) technique and Fourier transform infrared (FT-R) spectroscopy. The electronic states variations were investigated by Near Edge X-ray Absorption Fine Structure (NEXAFS). Photoluminescence (PL), Cathodoluminescence (CL). and Vacuum ultraviolet (VUV) spectrum were used for examining the optical properties. We report the optical property changes depending on crystal structure and the electronic states.

• Korean Journal of Materials Research
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• v.16 no.12
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• pp.761-765
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• 2006

[ $II-III_2-(S,Se)_4$ ] structured of phosphor has been used at various field because those have high luminescent efficiency and broad emission band. Among these phosphors, the europium doped $BaGa_2S_4$ was prepared by solid-state method and had high potential application due to an emissive property of UV region. Also, the common sulfide phosphors were synthesized by using injurious $H_2S\;or\;CS_2$ gas. However, in this study $BaGa_2S_4:Eu^{2+}$ phosphor in addition to excess sulfur was prepared under at 5% $H_2/95%\;N_2$ reduction atmosphere. Thus, this process could be considered as large scale synthesis because of non-harmfulness and simplification. The photoluminescence efficiency of the prepared $BaGa_2S_4:Eu^{2+}$ phosphor increased 20% than that of commercial $SrGa_2S_4:Eu^{2+}$ phosphor. The prepared $BaGa_2S_4:Eu^{2+}$ could be applied to green phosphor for white LED of three wavelengths.

• Korean Journal of Materials Research
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• v.16 no.3
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• pp.145-150
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• 2006

Various colors of light emitting diodes(LED) and four-band white light sources are obtained using a violet LED and various phosphor films. $BaMg_2Al_{16}O_{27}:Eu\;(blue),\;SrGa_2S_4:Eu\;(green),\;and\;Eu(TTA)_3(PTA)$ (red) phosphors are dispersed in poly-vinyl-alcohol aqueous solutions, and phosphor films are prepared by coating the suspensions to PET film. The narrow band emission of $Eu(TTA)_3(PTA)$ phosphor has excellent red luminescent property for four-band white light excited by the violet LED.

• Journal of Powder Materials
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• v.19 no.6
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• pp.442-445
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• 2012

The quantum dots (QD) have unique electrical and optical properties due to quantum dot confinement effect. The optical properties of QDs are decided by various synthesis conditions. In a prior QDs study, a study on the QDs size with synthesis condition such as synthesis time and temperature is being extensively researched. However, the research on QDs size with composition ratio has hitherto received scant attention. In order to evaluate the ratio dependence of CdSe crystal, synthesis ratio of Se precursor is changed from 16.7 mol%Se to 44 mol%Se. As the increasing Se ratio, the band gap was increased. This is caused by red shift of emission. We confirmed optical property of CdSe QDs with composition ratio.

• Korean Journal of Materials Research
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• v.17 no.6
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• pp.303-307
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• 2007

ZnO thin films were prepared by pulsed laser deposition on amorphous fused silica substrates at different ambient $O_2$ pressures varying from 0.5 to 500 mTorr, to observe the effect of ambient gas on their crystalline structure, morphology and optical properties. Results of X-ray diffraction, scanning electron microscopy, atomic force microscopy and photoluminescence studies showed that crystallinity, surface features and optical properties of the films significantly depended on the oxygen background pressure during growth. A low oxygen pressure (0.5 mTorr) seems to be suitable for the growth of highly c-axis oriented and smoother films possessing a superior luminescent property. The films grown at the higher $O_2$ pressures (50-500 mTorr) were found to have many defects probably due to an excessive incorporation of oxygen into ZnO lattice. We speculate that the film crystallinity could be affected by the kinetics of atomic arrangement during deposition at the higher oxygen pressures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05a
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• pp.102-105
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• 2004

With varying rapid thermal annealing (RTA) temperature, luminescent properties of ZnMgS:Mn thin film sputter-deposited with one target were measured. Although all samples have the same composition, $Zn_{1-x}Mg_xS:Mn$ (x=0.25) can emit luminescence between 580 and 614 nm, which is controlled by only RTA temperature. It is understood that the energy band gap shift of ZnMgS:Mn thin film phosphor occurs with varying RTA temperature.