• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12
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• pp.1121-1124
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• 2003

We report the photo (PL) and electro luminescence (EL) properties of new conjugated compounds based on imidazole moiety, 4,4' -di(4,5 diphenyl-N-imidazolyl)stilbene(DDPIS) and 4,4'-di(2,4,5-triphenyl-N-imidazolyl)stilbene(DTPIS), as emitting materials. ITO/m-MTDATA/NPB/DDPIS/Alq3/LiF/AI device shows blue EL spectrum at 456 ㎚ and 0.3 cd/ A and turn on voltage at 7 ∼ 8 V. DTPIS shows blue EL spectrum at around λmax=453㎚ and 0.5 cd/A efficiency in ITO/m-MTDATA/NPB/DTPIS/Alq3/LiF/Al device.

• Rapid Communication in Photoscience
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• v.2 no.1
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• pp.9-17
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• 2013

Visible light-sensitive $TiO_2$ and ZnO nanostructure materials have attracted great attention as the promising material for solar energy conversion systems such as photocatalysts for water splitting and environmental purification as well as nano-biosensors. Success of their applications relies on how to control their surface state behaviors related to the exciton dynamics and optoelectronic properties. In this paper, we briefly review some recent works on single nanoparticle photoluminescence (PL) technique and its application to observation of their surface state behaviors which are raveled by the conventional ensemble-averaged spectroscopic techniques. This review provides an opportunity to understand the temporal and spatial heterogeneities within an individual nanostructure, allowing for the potential use of single-nanoparticle approaches in studies of their photoenergy conversion and nano-scale optical biosensing.

• Journal of the Korean Ceramic Society
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• v.45 no.12
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• pp.821-826
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• 2008

Nanocrystallized glasses with the composition of $(50-x)BaO-xTiO_2-50SiO_2$ (x=10, 15, 16.7 and 20) have been prepared by heat-treatment at $T_x$ (crystallization onset temperature) for 3 h, and their optical properties, photoluminescence (PL), XRD and Raman spectra have been examined. The absorption edges of the glasses were red-shifted and the absorption coefficient increased with an increase of $TiO_2$. The glass subjected to the heat-treatment showed a dense formation of ${Ba_2}{TiSi_2}{O_8}$ crystals. The XRD and Raman results show that the nanocrystallized glasses formed fresnoite phase up to $TiO_2$ concentrations of 15 mol%. Further-more, blue luminescence with a peak at the wavelength of around 470nm was observed in the nanocrystallized glass, demon strating the optical multifunctional nanocrystallized material such as non-linear optics and photo-luminescence. It is thought that the blue luminescence from the ${Ba_2}{TiSi_2}{O_8}$ nanocrystallized glass originated from the presence of $Ti^{4+}$ incorporated into the fresnoite-type structure.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.4
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• pp.131-135
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• 2020

Single crystal phased CaZrO₃ : Eu³⁺ phosphor have been synthesized by skull melting method. The crystal structure, morphology and optical properties of synthesized phosphor were investigated XRD (X-ray diffraction), SEM (scanning electron microscopy), UV (ultraviolet) fluorescence reaction and PL (photo luminescence). The starting materials having chemical composition of CaO: ZrO₂ : Eu₂O₃= 0.962 : 1.013 : 0.025 mol% were charged into a cold crucible. The cold crucible was 120 mm in inner diameter and 150 mm in inner height, and 3 kg of mixed powder (CaO, ZrO₂ and Eu₂O₃) was completely melted within 1 hour at an oscillation frequency of 3.4 MHz, maintained in the molten state for 2 hours, and finally air-cooled. The XRD results show that synthesized phosphor is stabilized in orthorhombic perovskite structure without any impurity phases. The synthesized phosphor could be excited by UV light (254 or 365 nm) and the emission spectra results indicated that bright red luminescence of CaZrO₃ : Eu³⁺ due to magnetic dipole transition ⁵D₀→⁷F₂ at 615 nm was dominant.

• Transactions on Electrical and Electronic Materials
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• v.14 no.4
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• pp.208-210
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• 2013

ZnO films were deposited on glass substrates by radio frequency (RF) magnetron sputtering and exposed to intense electron beam irradiation to investigate the effects of electron irradiation on the properties of the films. Although all of the films had ZnO (002) textured structure regardless of electron irradiation, the grain sizes of the films decreased with electron irradiation. Surface roughness also depended on electron irradiation. The surface roughness varied between 2.3 and 1.6 nm, depending on the irradiation energy. Based on photoluminescence (PL) characterization, the most intense UV emission was observed from ZnO films irradiated at 900 eV. Since the intensity of UV emission is dependent upon the stoichiometric of ZnO films, we conclude that 900 eV was the optimum electron irradiation energy to achieve the best stoichiometric of ZnO films in this study.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.9
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• pp.32-37
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• 2008

Freestanding hydride vapor phase epitaxy grown GaN(Gallium Nitride) substrates subjected to various polishing methods were characterized for their surface and subsurface conditions, Although CMP(Chemical Mechanical Polishing) is one of the best approaches for reducing scratches and subsurface damages, the removal rate of Ga-polar surface in CMP is insignificant($0.1{\sim}0.3{\mu}m$/hr) as compared with that of N-polar surface, Therefore, conventional MP(Mechanical Polishing) is commonly used in the GaN substrate fabrication process, MP of (0001) surface of GaN has been demonstrated using diamond slurries with different abrasive sizes, Diamond abrasives of size ranging from 30nm to 100nm were dispersed in ethylene glycol solutions and mineral oil solutions, respectively. Significant change in the surface roughness ($R_a$ 0.15nm) and scratch-free surface were obtained by diamond slurry of 30nm in mean abrasive size dispersed in mineral oil solutions. However, MP process introduced subsurface damages confirmed by TEM (Transmission Electronic Microscope) and PL(Photo-Luminescence) analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.24-27
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• 2004

ZnS nanoparticles were synthesized and doped with $Pr^{3+}\;and\;Mn^{2+}$. Photoluminescence(PL) peaks were observed at 430 nm for pure ZnS, 585 nm for $Mn^{2+}-doped$ ZnS, and at around 430, 460, 480, 495 nm for ZnS nanoparticles doped with $Pr^{3+}$, respectively. For co-doped sample, both characteristics of doping with each element were exhibited. Optical annealing through UV irradiation was carried out in the two atmospheres; air and vacuum. The increases of the luminescence intensity was more considerable in the air, which is attributed to the photo-induced oxidation. In the case of co-doped sample the change of the emission color was observed by UV annealing.

• Korean Journal of Materials Research
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• v.9 no.6
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• pp.564-568
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• 1999

The 8-hydroxyquinoline Zinc(Znq2) were prepared successfully from zinc chloride and zinc acetate as two kinds of starting material. The organic electroluminescent devices(ELDs) were fabricated by the structure of ITO/TPD/Znq2/Al with N-N'-diphenyl-N-N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine(TPD) which acts hole trasporting layer and bis(8-oxyquinolino) zinc(II)(Znq2) which acts as emission and electron transporting layer. EL efficiency of Znq2 prepared by heating was investigated. The 570nm of main emission peak which is yellowich green was investigated by photo luminesence(PL) and this results shows that electro luminescence(EL) is from Znq2. The V-J curve shows that carrier injection were investigated from 4V. Maximum luminance and luminance efficiency were 1600cd/$\m^2$, 0.9lm/W. From this results, the Znq2 can be one of the useful organic EL material.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.340-341
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• 2013

양자점(Quantum dots; QDs)은 단전자 트랜지스터, 레이저, 발광다이오드, 적외선 검출기와 같은 고효율 광전소자 응용을 위해 활발한 연구가 진행되고 있다. II-VI 족 화합물 반도체는 III-V 족 화합물 반도체와 비교했을 때 더 큰 엑시톤 결합에너지(exciton binding energy)를 가지는 우수한 특성을 보이고 있으며 이러한 성질을 가지는 II-VI 족 화합물 반도체 중에서도 넓은 에너지 갭을 가지는 CdTe 양자점은 녹색 영역대의 광전자 소자로서 활용되고 있다. 기존의 CdTe/ZnTe 양자점을 성장하기 위해 ZnTe와 격자부정합이 적은 GaAs 기판을 이용한 연구가 주를 이룬 반면 Si기판을 이용한 연구는 미흡하다. 하지만 Si 기판은 GaAs 기판에 비해 값이 싸고, 여러 분야에 응용이 가능하며 대량생산이 가능하다는 이점을 가지고 있어 초고속, 초고효율 반도체 광전소자의 제작을 가능케 할 것으로 기대된다. 또한 양자점의 고효율 광전소자에 응용을 위해서는 Si 기판 위에 양자점의 크기를 효율적으로 조절하는 연구 뿐 아니라 양자점의 크기에 따른 운반자 동역학에 대한 연구도 중요하다. 본 연구에선 분자선 에피 성장법(Molecular Beam Epitaxy; MBE)과 원자층 교대 성장법(Atomic Layer Epitaxy; ALE)을 이용하여 Si 기판 위에 성장한 CdTe/ZnTe 양자점의 크기에 따른 광학적 특성을 연구하였다. 저온 광 루미네센스(PhotoLuminescence; PL) 측정 결과 양자점의 크기가 증가함에 따라 더 낮은 에너지영역으로 피크가 이동하는 것을 확인하였다. 그리고 온도 의존 광루미네센스 측정 결과 양자점의 크기가 증가함에 따라 열적 활성화 에너지가 증가하는 것을 관찰하였는데, 이는 양자점의 운반자 구속효과가 증가하였기 때문이다. 또한 시분해 광루미네센스 측정 결과 CdTe/ZnTe 양자점의 크기가 증가함에 따라 소멸 시간이 긴 값을 갖는 것을 관찰하였는데, 이는 양자점의 크기가 증가함에 따라 엑시톤 진동 세기가 감소하였기 때문이다. 이와 같은 결과 Si 기판 위에 성장한 CdTe/ZnTe 양자점의 크기에 따른 열적 활성화 에너지와 운반자 동역학에 대해 이해 할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.213-213
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• 2013

화합물 반도체 양자점(Quantum dots; QDs)은 높은 효율의 광전자 소자에 적용할 수 있기 때문에 이분야에 대한 연구가 활발히 진행되고 있지만 주로 III-V 족 화합물 반도체에 대한 연구가 주를 이룬 반면 II-VI 족 화합물 반도체에 대한 연구는 아직 미흡하다. 하지만 II-VI 족 화합물 반도체는 III-V 족 화합물 반도체와 비교했을 때 더 큰 엑시톤 결합에너지(exciton binding energy)를 가지는 우수한 특성을 보이고 있으며 이러한 성질을 가지는 II-VI 족 화합물 반도체 중에서도 넓은 에너지 갭을 가지는 $Cd_xZn_{1-x}Te$ 양자점은 녹색 영역대의 광전자 소자로서 활용되고 있다. 현재 대부분의 $Cd_xZn_{1-x}Te$ 양자점 구조는 기판과 완충층 (buffer layer) 사이의 작은 격자 부정합(lattice mismatch) 때문에 GaAs 기판을 이룬 반면 Si기판을 이용한 연구는 미흡하다. 하지만 Si 기판은 GaAs 기판에 비해 값이 싸고, 여러 분야에 응용이 가능하며 대량생산이 가능하다는 이점을 가지고 있어 초고속, 초고효율 반도체 광전소자의 제작을 가능케 할 것으로 기대된다. 또한 양자점의 고효율 광전소자에 응용을 위해서는 Si 기판 위에 양자점의 크기를 효율적으로 조절하는 연구 뿐 아니라 양자점의 크기에 따른 운반자 동역학에 대한 연구도 중요하다. 본 연구에선 분자선 에피 성장법(Molecular Beam Epitaxy; MBE)을 이용하여 Si 기판위에 성장한 $Cd_xZn_{1-x}Te/ZnTe$ 양자점의 크기에 따른 광학적 특성을 연구하였다. 저온 광 루미네센스 (PhotoLuminescence; PL) 측정 결과 양자점의 크기가 증가함에 따라 더 낮은 에너지영역으로 피크가 이동하는 것을 확인하였다. 그리고 시분해 광루미네센스 측정 결과 $Cd_xZn_{1-x}Te/ZnTe$ 양자점의 크기가 증가함에 따라 소멸 시간이 긴 값을 갖는 것을 관찰 하였는데, 이는 양자점의 크기가 증가함에 따라 엑시톤 진동 세기가 감소하였기 때문이다. 또한 온도 의존 광루미네센스 측정 결과 양자점의 크기가 증가함에 따라 열적 활성화 에너지가 증가하는 것을 관찰 하였는데, 이는 양자점의 운반자 구속효과가 증가하였기 때문이다. 이와 같은 결과 Si 기판 위에 성장한 $Cd_xZn_{1-x}Te/ZnTe$ 양자점의 크기에 따른 광학적 특성에 대해 이해 할 수 있었다.