• Transactions on Electrical and Electronic Materials
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• 제14권1호
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• pp.24-27
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• 2013

In this paper, we investigated the effect of luminescence properties of various concentrations of magnesium-doped ZnS:Mn phosphor excited by plasma luminescence device. The PL intensity was evaluated in the range of 300~500 nm excitation wavelengths. We found the highest PL intensity of the phosphors excited by 365 nm and 450 nm was observed at Mg concentrations of 1.4 wt% and 0.8 wt%, respectively. In addition, an emission peak was distinguished at 580 nm wavelength. With increasing Mg dopant level, enhanced PL intensity was observed, which is possibly applicable to color converting materials by blue emission for white light sources. Finally, we evaluated the luminance properties of color converting ZnS:Mn,Mg phosphors with plasma blue light source. the white luminance of plasma light source with CIE(0.36,0.26) was established by color converting phosphors of ZnS:Mn with 0.8 wt% Mg.

• Transactions on Electrical and Electronic Materials
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• 제12권5호
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• pp.218-221
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• 2011

We modified the optical properties of the $CuInS_2$ nanocrystal (NC) by alloying. Nanocrystals (NCs) with alloyed cores were synthesized by refluxing the as-synthesized $CuInS_2$ NCs with a mixture of cadmium acetate, zinc acetate and palmitic acid. The shift in emission wavelength of the NCs after shell layer formation was minimized by alloying. The photoluminescence (PL) spectra showed significant reduction of emission intensity. A detailed study on the emission process of NCs implies that the formation of shell layers with small lattice mismatch minimized the mismatch strain generated from the shell layers in contrast to core alloyed NCs. In particular, time-resolved PL spectra of the NCs showed a significant increase in the lifetime of excited carriers by modifying the band alignment of the NCs by modifying the shell composition.

• The Korean Journal of Ceramics
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• 제3권4호
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• pp.245-248
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• 1997

Photoluminescence (PL) and cathodoluminescence (CL) characteristics of Ce-activated $Y_{2-x}Ce_xSiO_5$ have been investigated as functions of Ce concentration and firing condition. According to the X-ray, PL and CL results, $Y_2SiO_5$ is found to have two phases depending on the firing temperature. For the specimen fired above 127$0^{\circ}C$, the emission band peaked at 395nm with a shoulder at 424 nm under ultraviolet (u.v.) and cathode-ray (c.r.) excitation. However, for the specimen fired below 120$0^{\circ}C$ in air the peak was observed at 424 nm and it shifted to longer wavelength with reduction level. The reduced specimen for x=0.02 showed the brightest emission under u.v. excitation whereas under c.r. excitation the brightest emission was observed for the reduced specimen for x=0.06.

• 대한화학회지
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• 제26권4호
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• pp.224-228
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• 1982

chl-b를 소중합체로서 용매에 녹였을 때 친핵성 n-prOH를 첨가함에 따라 흡광도와 fluorescence emission의 세기는 증가하였지만 단위체로 녹은 다음에 n-prOH의 농도증가에 따라 점차 감소하였다. chl-b는 소중합체의 생성때문에 Beer 법칙에 따르지 않았으며 용매의 극성변화에 따라 stockes shift를 나타냈다. 이러한 경향성은 chl-b의 정량에 고려하여야될 점이다.

• 한국표면공학회지
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• 제46권2호
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• pp.93-97
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• 2013

We studied the emission characteristics of white phosphorescent organic light-emitting diodes (PHOLEDs), which were fabricated using a two-wavelength method. To optimize emission characteristics of white PHOLEDs, white PHOLEDs with co-doping and blue/co-doping emitting layer (EML) structures were fabricated using a host-dopant system. The total thickness of light-emitting layer was 25 nm and the dopant of blue and red was FIrpic and $Bt_2Ir(acac)$ in UGH3, respectively. In case of co-doping structure, applying micro lens array film showed efficiency improvement from the current efficiency 78.5 cd/A and power efficiency 40.4 lm/W to the current efficiency 131.1 cd/A and power efficiency 65 lm/W and blue / co-doping structure showed efficiency improvement from the current efficiency 43.8 cd/A and power efficiency 22 lm/W to the current efficiency 69 cd/A and power efficiency 32 lm/W.

• 한국표면공학회지
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• 제48권3호
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• pp.105-109
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• 2015

We studied emission characteristics of blue fluorescent multi-tandem OLEDs using $Al/MoO_x$ as charge generation layer(CGL). Threshold voltage for 2, 3, 4, and 5 units tandem OLEDs was 8, 11, 14 and 18 V, respectively. The threshold voltage in multi-tandem OLEDs was lower than multiple of 4 V for the single OLED. Maximum current efficiency and maximum quantum efficiency of single OLED were 7.6 cd/A and 5.5%. Maximum current efficiency for 2, 3, 4, and 5 units tandem OLEDs was 22.6, 31.4, 41.2, and 46.6 cd/A, respectively. Maximum quantum efficiency for 2, 3, 4, and 5 units tandem OLEDs was 11.8, 15.8, 21.8, and 25.6%, respectively. The maximum current efficiency and maximum quantum efficiency in multi-tandem OLEDs were higher than multiple of those for the single OLED. The intensity for 508 nm peak was changed and the peak wavelength was red shift by increase of tandem unit in electroluminescent emission spectra. These phenomena can be caused by micro-cavity effect with increasing of organic layer thickness.

• 분석과학
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• 제21권4호
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• pp.279-283
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• 2008

혈토와 규사토, 맥반석, 혈토를 혼합한 물질을 $1100^{\circ}C$에서 소형 및 소결하여 원적외선 방사물질 볼로 사용하였다. 각각 제조된 볼의 방사에너지는 $8{\sim}12{\mu}m$ 파장 범위에서 상대적으로 높았다. 혼합 볼의 이온용출은 소량이고, 혼합 볼로 처리된 활성수와 에너지수의 중금속인 $Cd^{2+}$ 이온 제거능력은 높았다. 활성수와 에너지수는 음용수보다는 상대적으로 UV 차단효과가 높았다.

• 한국결정성장학회지
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• 제18권4호
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• pp.160-164
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• 2008

절연성 및 전도성 12CaO ${\cdot}7Al_2O_3$ (Cl2A7)이 도핑된 ITO 박막을 유리기판 위에 radio frequency(rt) magnetron 스퍼터링 방법으로 절연성 및 전도성 Cl2A7 타겟 칩의 개수를 변화시키면서 증착하였다. 이러한 박막들의 구조적, 전기적, 광학적 특성을 살펴보았다. Cl2A7 타겟 칩의 개수가 증가함에 따라 박막의 캐리어 농도는 감소하고, 비저항은 증가하였다. 박막의 광 투과도는 가시광 영역에서는 80% 이상의 값으로 나타났다. Grain의 크기의 변화는 결정성과 표면 거칠기에 크게 영향을 미친다는 것이 확인되었다.

• Applied Science and Convergence Technology
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• 제26권4호
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• pp.79-85
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• 2017

The crack-free AlGaN template has been successfully grown by using selective area growth with triangular GaN facet. The triangular GaN stripe structure was obtained by vertical growth rate enhanced mode with low growth temperature of $950^{\circ}C$ and high growth pressure of 500 torr. The lateral growth rate enhanced mode of AlGaN for crack-free and flat surface was also investigated. Low pressure of 30 torr and high V/III ratio of 4400 were favorable for lateral growth of AlGaN. It was confirmed that the $4{\mu}m$ -thick $Al_{0.2}Ga_{0.8}N$ was crack-free over entire 2-inch wafer. The dislocation density of $Al_{0.2}Ga_{0.8}N$ was as low as ${\sim}7.6{\times}10^8/cm^2$ measured by cathodoluminescence. Based on the high quality AlGaN with low dislocation density, the ultraviolet laser diode epitaxy with cladding, waveguide and GaN/AlGaN multiple quantum well (MQW) was grown by metalorganic chemical vapor deposition. The stimulated emission at 349 nm with full width at half maximum of 1.8 nm from the MQW was observed through optical pumping experiment with 193 nm KrF laser. We also have fabricated the deep ridge type ultraviolet laser diode (UV-LD) with $5{\mu}m-wide$ and $700{\mu}m-long$ cavity for electrical properties. The turn on voltage was below 5 V and the resistance was ${\sim}55{\Omega}$ at applied voltage of 10 V. The amplified spontaneous emission spectrum of UV-LD was also observed from pulsed current injection.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.184-184
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• 2012

Recently, InGaN/GaN multi-quantum well grown on GaN pyramid structures have attracted much attention due to their hybrid characteristics of quantum well, quantum wire, and quantum dot. This gives us broad band emission which will be useful for phosphor-free white light emitting diode. On the other hand, by using quantum dot emission on top of the pyramid, site selective single photon source could be realized. However, these structures still have several limitations for the single photon source. For instance, the quantum efficiency of quantum dot emission should be improved further. As detection systems have limited numerical aperture, collection efficiency is also important issue. It has been known that micro-cavities can be utilized to modify the radiative decay rate and to control the radiation pattern of quantum dot. Researchers have also been interested in nano-cavities using localized surface plasmon. Although the plasmonic cavities have small quality factor due to high loss of metal, it could have small mode volume because plasmonic wavelength is much smaller than the wavelength in the dielectric cavities. In this work, we used localized surface plasmon to improve efficiency of InGaN qunatum dot as a single photon emitter. We could easily get the localized surface plasmon mode after deposit the metal thin film because lnGaN/GaN multi quantum well has the pyramidal geometry. With numerical simulation (i.e., Finite Difference Time Domain method), we observed highly enhanced decay rate and modified radiation pattern. To confirm these localized surface plasmon effect experimentally, we deposited metal thin films on InGaN/GaN pyramid structures using e-beam deposition. Then, photoluminescence and time-resolved photoluminescence were carried out to measure the improvement of radiative decay rate (Purcell factor). By carrying out cathodoluminescence (CL) experiments, spatial-resolved CL images could also be obtained. As we mentioned before, collection efficiency is also important issue to make an efficient single photon emitter. To confirm the radiation pattern of quantum dot, Fourier optics system was used to capture the angular property of emission. We believe that highly focused localized surface plasmon around site-selective InGaN quantum dot could be a feasible single photon emitter.