• 한국표면공학회지
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• 제47권4호
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• pp.192-197
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• 2014

Red-emitting nitride phosphors recently attracted considerable attention because of their high thermal stability and high color rendering index properties. For excellent phosphor of white light-emitting-diode, ternary nitride phosphor of $Sr/SmSi_5N_8:Eu^{2+}$ with different $Eu^{2+}$ ion concentration were synthesized by solid state reaction method. In this work, red-emitting nitride $Sr/SmSi_5N_8:Eu^{2+}$ phosphor was successfully synthesized by using multi-step high frequency induction heat treatment. 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 $Sr/SmSi_5N_8:Eu^{2+}$ phosphors were investigated by XRD and photoluminescence spectroscopy. The excitation spectra of $Sr/SmSi_5N_8:Eu^{2+}$ phosphors indicated broad excitation wavelength range of 300 - 550 nm, namely from UV to visible area with distinct enhanced emission peaks. With an increase of $Eu^{2+}$ ion concentration, the peak position of emission in spectra was red-shifted from 613 to 671 nm. After via multi-step heat treatment, prepared phosphor showed excellent luminescence properties, such as high emission intensity and low thermal quenching, better than commercial phosphor of $Y_3Al_5O_{12}:Ce^{3+}$. Using $Eu_2O_3$ as a raw material for $Eu^{2+}$ dopant with nitrogen gas flowing instead of using commercial EuN chemical for $Sr/SmSi_5N_8:Eu^{2+}$ synthesis is one of characteristic of this work.

• 영재교육연구
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• 제20권3호
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• pp.901-919
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• 2010

본 연구에서는 중학교 과학영재학생들과 일반학생들의 첨단과학에 대한 기본 인식 및 관련 지식을 비교하기 위하여 설문도구를 제작하여 투입한 후 결과를 분석하였다. 과학영재집단은 부산, 울산 지역 대학부설 과학영재교육원 소속 중학생 113명이었고 일반학생 집단은 부산광역시 소재 2개 중학교의 159명이었다. 설문문항은 첨단과학에 대한 기초인식 조사와 관련 지식 조사 두 가지 분야로 구성하였다. 기초인식 조사 결과, 첨단과학 전반에 대한 인지도 수준 및 관심과 흥미 측면에서 과학영재학생이 일반학생보다 유의미하게 높게 나타났다. 첨단과학에서 알고 싶은 분야, 첨단과학 관련 정보의 출처, 첨단과학에 대한 교수 학습 방법의 선호도 등에서도 과학영재학생과 일반학생 간에 차이가 나타났다. 실생활과 관련이 깊은 첨단기술인 휴대폰과 LED를 소재로 구체적인 지식을 조사한 결과, 안테나 없는 휴대폰과 LED의 배경 지식인 전자기파나 반도체에 대해서 과학영재학생들은 일반학생들보다 상대적으로 높은 이해도를 보여주었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.50-50
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• 2008

ZnO has been extensively studied for optoelectronic applications such as blue and ultraviolet (UV) light emitters and detectors, because it has a wide band gap (3.37 eV) anda large exciton binding energy of ~60 meV over GaN (~26 meV). However, the fabrication of the light emitting devices using ZnO homojunctions is suffered from the lack of reproducibility of the p-type ZnO with high hall concentration and mobility. Thus, the ZnO-based p-n heterojunction light emitting diode (LED) using p-Si and p-GaN would be expected to exhibit stable device performance compared to the homojunction LED. The n-ZnO/p-GaN heterostructure is a good candidate for ZnO-based heterojunction LEDs because of their similar physical properties and the reproducibleavailability of p-type GaN. Especially, the reduced lattice mismatch (~1.8 %) and similar crystal structure result in the advantage of acquiring high performance LED devices with low defect density. However, the electroluminescence (EL) of the device using n-ZnO/p-GaN heterojunctions shows the blue and greenish emissions, which are attributed to the emission from the p-GaN and deep-level defects. In this work, the n-ZnO:Ga/p-GaN:Mg heterojunction light emitting diodes (LEDs) were fabricated at different growth temperatures and carrier concentrations in the n-type region. The effects of the growth temperature and carrier concentration on the electrical and emission properties were investigated. The I-V and the EL results showed that the device performance of the heterostructure LEDs, such as turn-on voltage and true ultraviolet emission, developed through the insertion of a thin intrinsic layer between n-ZnO:Ga and p-GaN:Mg. This observation was attributed to a lowering of the energy barriers for the supply of electrons and holes into intrinsic ZnO, and recombination in the intrinsic ZnO with the absence of deep level emission.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.25-27
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• 2007

$Eu^{2+}$-doped $Ca_2Si_5N_8$ was grown on Si(100) substrate using metal-organic deposition (MOD) method and post-annealed at $900^{\circ}C$ in various atmosphere. Luminescence properties of these thin films were investigated with variations of $Eu^{2+}$-doped concentrations and annealing atmosphere. Thin film was formed with clean surface and uniform thickness of about 72 nm. From the measurements of luminescence properties of thin films, film must be post-annealed in nitrogen or mixture of nitrogen and hydrogen atmosphere to emit a sufficient light. For $Ca_{1.5}Eu_{0.5}Si_5N_8$ thin film annealed at $900^{\circ}C$ in nitrogen atmosphere, excitation band from 380 to 420 nm was detected with the maximum intensity at 404 nm and two broad emission bands from 530 to 630 nm were observed. These broad excitation and emission bands must be attributed to the nitrogen incorporations into the films. From the results, $Ca_{2-x}Eu_xSi_5N_8$ thin film has probability for next generation thin film lighting applications such as light emitting diode (LED) or electro-luminescence (EL).

• 반도체디스플레이기술학회지
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• 제18권4호
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• pp.51-56
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• 2019

LuAG:Ce(Lu₃Al₅O₁₂:Ce³⁺) nano phosphor were synthesized by applying the coprecipitation method. It is used to increase the color rendering of phosphor ceramic plate for high power LEDs and laser lighting. Internal quantum efficiency and absorption of LuAG:Ce nano phosphor are 51.5 % and 64.4 %, respectively, which is higher than the previously studied nano phosphors. The maximum absorption wavelength of this phosphor is 450 nm blue light, and the emission wavelength is 510 nm. The emission wavelength shifted to longer wavelength when the concentration of Ce increased in the heat treatment of the reducing atmosphere. Thermal quenching of LuAG nano phosphor was 70 % at 200 ℃, it was explained by their significant quenching of all raman scattering modes, implying the restriction of electron-phonon couplings caused by their defects.

• 한국재료학회지
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• 제16권12호
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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.

• 한국재료학회지
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• 제18권11호
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• pp.623-627
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• 2008

For possible applications as luminescent materials for white-light emission using UV-LEDs, $Ba_2Mg(PO_4)_2:Eu^{2+}$ phosphors were prepared by a solid state reaction. The photoluminescence properties of the phosphor were investigated under ultraviolet ray (UV) excitation. The prepared phosphor powders were characterized to from a single phase of a monoclinic crystalline structure by a powder X-ray diffraction analysis. In the photoluminescence spectra, the $Ba_2Mg(PO_4)_2:Eu^{2+}$ phosphor showed an intense emission band centered at the 584 nm wavelength due to the f-d transition of the $Eu^{2+}$ activator. The optimum concentration of $Eu^{2+}$ activator in the $Ba_2Mg(PO_4)_2$ host, indicating the maximum emission intensity under the excitation of a 395 nm wavelength, was 5 at%. In addition, it was confirmed that the $Eu^{2+}$ ions are substituted at both $Ba^{2+}$ sites in the $Ba_2Mg(PO_4)_2$ crystal. On the other hand, the critical distance of energy transfer between $Eu^{2+}$ ions in the $Ba_2Mg(PO_4)_2$ host was evaluated to be approximately 19.3 A. With increasing temperature, the emission intensity of the $Ba_2Mg(PO_4)_2$:Eu phosphor was considerably decreased and the central wavelength of the emission peak was shifted toward a short wavelength.

• Journal of Korean Vacuum Science & Technology
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• 제4권2호
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• pp.47-49
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• 2000

We report on the fabrication and characterization of InGaN/GaN multiple quantum well light emitting diode (LED) with a highly transparent Pt ohmic contact as a current spreading layer. The value of light transmittance of a Pt thin film with a thickness of 8 m on p-GaN was measured to be 85% at 450nm. The peak wavelength and the full-width at half-maximum (FWHM) of the emission spectrum of the LED at 20 mA were 453 m and 23 m, respectively. Pt-contacted LEDs show good electrical properties and high light-output efficiency compared to Ni/Au-contacted ones. These results suggest that a Pt thin film can be used as an effective current spreading layer with high light-transparency.

• Journal of Korean Vacuum Science & Technology
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• 제4권3호
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• pp.78-80
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• 2000

We reprot on the fabrication and characterization of InGaN/GaN multiple quantum well light-emitting diode (LED) with a highly transparent Pt ohmic contact as a current spreading layer. The value of light transmittance of a Pt thin film with a thickness of 8 nm on-GaN was measured to be 85% at 450 nm. The peak wavelength and the full-width at half-maximum (FWHM) of the emission spectrum of the LED at 20 mA were 453 nm and 23 nm, respectively. Pt-contacted LEDs show good electrical properties and high light-output efficiency compared to Ni/Au-contacted ones. These results suggest that a Pt thin film can be used as an effective current spreading layer with high light-transparency.

• 한국기후변화학회지
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• 제4권3호
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• pp.211-219
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• 2013

장기에너지 분석모형인 LEAP 모형을 활용하여 S시 가정 부문의 에너지 소비량 및 온실가스 배출 현황과 온실가스 저감대책에 따른 감축잠재량을 분석하였다. 2009년 S시의 에너지 소비량은 가정 상업부문에서 39.1%로 가장 많이 소비하고 있다. 또한, 가구수 증가로 인해 가정 부문의 에너지 및 온실가스 배출량이 증가할 것으로 전망되고 있어, 가정 부문의 온실가스 저감대책 마련이 시급한 상황이다. 이에 본 연구에서는 S시 가정 부문의 에너지 소비량을 파악하고, S시에 적합한 가정 부문 온실가스 저감대책을 수립하였다. 온실가스 감축 잠재량 예측을 위한 시나리오는 기준시나리오, LED 조명 보급, 에너지 대체, 녹색생활 실천, 통합 저감대책 등 총 5개 대책의 효과를 분석하였다. 2020년 기준 저감대책별 온실가스 배출량을 살펴보면, LED 조명 보급은 2020년 온실가스 배출량이 1,181.0천 $tonCO_2eq$로 기준시나리오 대비 약 6.1%의 감축효과가 나타났으며, 에너지 대체는 1,171.6천 $tonCO_2eq$으로 기준시나리오 대비 약 6.8%의 감축효과가 나타났다. 또한, 녹색생활 실천의 2020년 온실가스 배출량은 1,128.7천 $tonCO_2eq$로 기준시나리오 대비 약 10.2%의 온실가스 배출량을 줄일 수 있다는 결과를 도출할 수 있다. LED 조명 보급, 에너지 대체, 녹색생활 실천을 모두 통합한 통합 저감대책은 2020년 966.9천 $tonCO_2eq$로 기준시나리오 대비 약 23.1%의 온실가스 배출량을 줄일 수 있다는 것으로 나타났다.