BUSANIL Science High School

Busan, South Korea

BUSANIL Science High School

Busan, South Korea
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Shin S.S.,Silla University | Yi S.S.,Silla University | Park S.J.,Busanil Science High School | Hong C.B.,Busanil Science High School | And 6 more authors.
New Physics: Sae Mulli | Year: 2016

Tm3+ and Yb3+ co-doped LaNbO4 polycrystalline powders were prepared by using a solid-state reaction method, and their crystallinities and surface morphologies were analyzed by using X-ray diffraction and scanning electron microscopy, respectively. According to the results of X-ray diffraction, the powders showed a polycrystalline monoclinic structure. The photoluminescence and the upconversion luminescence properties of (La0.875-xYb0.125)NbO4:Tm3 x +(x = 0.006, 0.008, 0.01, 0.03 and 0.05) phosphors were investigated in detail. Blue upconversion emissions were observed in the phosphors under excitation by 980 nm laser diode. The powders exhibited strong blue upconversion emission peaks at 476 nm. The maximum emission intensity was obtained for the 0.006 mol Tm3+-doped powders, and intensity decreased as the concentration of Tm3+ ions was increased to 0.05 mol.


Choi S.W.,Silla University | Shin S.S.,Silla University | Yi S.S.,Silla University | Kim I.K.,Busanil Science High School | And 6 more authors.
New Physics: Sae Mulli | Year: 2016

Er3+ and Yb3+ co-doped GdVO4 polycrystalline powders were prepared by using a solid-state reaction method, and their crystallinity and surface morphology were analyzed by using X-ray diffraction and scanning electron microscopy, respectively. According to the X-ray diffraction results, the crystallinity of the powders showed a polycrystalline tetragonal structure. Photoluminescence and the upconversion luminescence properties of (Gd0.94-xYb0.06)VO4:Erx(x = 0, 0.02, 0.04 and 0.06) phosphors were investigated in detail. The red and the green upconversion emissions were observed in the phosphors under excitation by using a 980 nm laser diode. The powders exhibited strong green and red upconversion emission peaks at 553 and 660 nm, respectively. Also, their upconversion processes were explained by measuring the dependence of the upconversion luminescence on the pump's power intensity. © 2016, Korean Physical Society. All rights reserved.


Joo J.S.,Pukyong National University | Yang H.K.,Pukyong National University | Kim G.H.,Busanil Science High School | Kim B.G.,Busanil Science High School | Kim J.H.,Busanil Science High School
New Physics: Sae Mulli | Year: 2017

A high powered light-emitting diode (LED) chip elevates heat generation, which has led to in- creased interest in that development of heat radiation materials. A heat-radiation polymer composite composed of metal particle fillers has been researched due to its being easier to manufacture than metal-based heat-radiation materials. Poly lactic acid (PLA) is converted from glucose extracted from the starch of biomass and has been used in many fields as an environmentally friendly resin. In this study, a biodegradable composite plastic was produced by mixing activated carbon, PLA resin, and one metal from among aluminum, copper and iron. The components of metal-additive biodegradable composite plastics were investigated by using energy dispersive X-ray spectroscopy (EDS). The biodegradable composite plastic consisting of aluminum and activated carbon with a 1:1 mass ratio exhibited the highest thermal conductivity, 0.914 W/(m K). Once synthesized, the biodegradable composite plastics were used as heat sinks; as a result of them the temperature of each LED chip did not reach 50 °C after 30 min of LED operation. Our results suggest that biodegradable composite plastics may replace current heat sinks.


C.R. Kesavulu,Changwon National University | Lee D.G.,Silla University | Yi S.S.,Silla University | Jang K.,Changwon National University | And 5 more authors.
Journal of Alloys and Compounds | Year: 2013

Eu3+-activated novel alkaline earth metal (Sr and Ba) vanadate phosphors, Na(Sr0.97-x,Bax)VO4:Eu3+ 0:03 (x = 0-0.97) have been successfully synthesized using solid state reaction method and characterized through structure, morphology, elemental analysis, luminescence (excitation, emission and CIE coordinate) and decay rate properties as a function of Ba ion concentration. Phosphors show a broad excitation band (monitored for 5D0→7F 2 transition of Eu3+) in the 230-430 nm wavelength regions which make them highly suitable for GaN-based LED chips. These phosphors can be efficiently excited by near UV light and exhibit a dominant red emission at 613 nm 5D0→7F2. The decay lifetime and color coordinates were evaluated for Na(Sr,Ba)VO4:Eu 3+ phosphors. Hence, these phosphors could be a potential candidate for light emitting diodes and display applications. © 2013 Published by Elsevier B.V.


Kim M.,Busanil Science High School | Kim M.G.,Busanil Science High School | Kim S.R.,Busanil Science High School | Chung H.Y.,Busanil Science High School | And 5 more authors.
Journal of the Korean Physical Society | Year: 2013

We investigate the surface modification of a germanium epitaxial layer grown on a silicon substrate by means of an atmospheric-pressure plasma jet. The plasma jet contains a large density of highly reactive radicals, as confirmed by optical emission spectra. The plasma jet with a nozzle with a round end has a higher current level compared to cylindrical and pencil-shaped nozzles, indicating the usefulness of this plasma jet for semiconductor processing. Raman spectra reveal a significant modification of the germanium surface under exposure to an atmospheric pressure plasma jet even for 1 min. The first-order Raman peak at 320 cm-1 has an asymmetric shoulder on the low-frequency side, which can be attributed to amorphization/oxidation of the germanium layer due to highly reactive radicals. The rapid surface change under short-time exposure indicates the practicality of the plasma jet for semiconductor processing. © 2013 The Korean Physical Society.

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