• 한국전기전자재료학회논문지
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• 제24권1호
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• pp.27-31
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• 2011

ZnS:Mn yellow phosphors doped with Sm for white light emitting diodes were synthesized by solid state reaction method. These sample showed the characteristic X-ray diffraction patterns for main peak (110) of ZnS:Mn,Sm. Photoluminescence excitation spectra originated from $Mn^{2+}$ were ranged from 450 nm to 500 nm. The yellow emission at around 580 nm was associated with $^4T_1{\rightarrow}^6A_1$ transition of $Mn^{2+}$ ions in ZnS:Mn,Sm phosphors. The highest photolum inescence intensity of the phosphors under 405 nm and 450 nm excitation was obtained at Sm concentration of 1 mol%. The enhanced photoluminescent intensity in the ZnS:Mn,Sm phosphors was interpreted by energy transfer from Sm to Mn. The highest luminescent intensity of white LED was obtained at the epoxy-to-yellow phosphor ratio of 1:3. At this ratio, the CIE chromaticity of the white LED was X=0.3886 and Y=0.2928.

• 한국세라믹학회지
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• 제38권9호
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• pp.817-821
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• 2001

새로운 형광체로 역스피넬 구조를 갖는 $Mg_{2-x}MN_xSnO_4$ 조성을 선정하여 고상반응에 의하여 제조하였다. $Mg_2SnO_4:Mn$의 광발광 특성이 147nm 파장의 진공 자외선 여기하에 측정되었다. Mn의 첨가에 의하여 $Mg_2SnO_4$ 형광체는 500nm 파장에 발광 중심을 가지며 매우 높은 발광강도를 나타내었다. 이것은 스피넬 구조의 산소 사면체 배위에 위치하는 Mg 자리를 치환하여 들어가는 $Mn^{2+}$ 이온의 $^4T_1$ 상태로부터 $^6A_1$ 상태로의 에너지 전이에 의한 발광으로 해석되었다. 진공 자외선 여기하에 최대의 발광강도를 나타내는 Mn 활성제의 농도는 0.25mol%이었고, 잔광시간은 10ms 이하인 것으로 조사되었다.

• 한국표면공학회지
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• 제49권1호
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• pp.81-86
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• 2016

$Eu^{3+}$-doped $MgMoO_4$ phosphor thin films were deposited on quartz substrates by radio frequency magnetron sputtering with changing various growth temperatures. The effects of growth temperature on the structure, transmittance, optical band gap, and luminescence of the phosphor thin films were characterized. All the phosphor thin films, irrespective of growth temperature, showed a monoclinic structure with a main (220) diffraction peak. The thin film deposited at a growth temperature of $400^{\circ}C$ indicated an average transmittance of 90% in the wavelength range of 500 ~ 1100 nm and band gap energy of 4.81 eV. The excitation spectra of the phosphor thin films consisted of a broad charge transfer band peaked at 284 nm in the range of 230 ~ 330 nm and two weak peaks located at 368 and 461 nm, respectively. The emission spectra under ultraviolet excitation at 284 nm exhibited a sharp emission peak at 614 nm and several weak bands. All the phosphor thin films showed high asymmetry ratio values, indicating that $Eu^{3+}$ ions incorporated into the host lattice occupied at the non-inversion symmetry sites. The results suggest that the growth temperature plays an important role in growing high-quality phosphor thin films.

• 한국표면공학회지
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• 제56권3호
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• pp.201-207
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• 2023

Eu³⁺-doped SnO² (SnO²:Eu³⁺) phosphor thin films were grown on quartz substrates by radio-frequency magnetron sputtering. The deposition temperature was varied from 100 to 400 ℃. The X-ray diffraction patterns showed that all the thin films had two mixed phases of SnO₂ and Eu₂Sn₂O₇. The 880 nmthick SnO²:Eu³⁺ thin film grown at 100 ℃ exhibited numerous pebble-shaped particles. The excitation spectra of SnO²:Eu³⁺ thin films consisted of a strong and broad peak at 312 nm in the vicinity from 250 to 350 nm owing to the O^2--Eu3+ charge transfer band, irrespective of deposition temperature. Upon 312 nm excitation, the SnO²:Eu³⁺ thin films showed a main emission peak at 592 nm arising from the ⁵D₀→⁷F₁ transition and a weak 615 nm red band originating from the ⁵D₀→⁷F₂ transition of Eu³⁺. As the deposition temperature increased, the emission intensities of two bands increased rapidly, approached a maximum at 100 ℃, and then decreased slowly at 400 ℃. The thin film deposited at 200 ℃ exhibited a band gap energy of 3.81 eV and an average transmittance of 73.7% in the wavelength range of 500-1100 nm. These results indicate that the luminescent intensity of SnO²:Eu³⁺ thin films can be controlled by changing the deposition temperature.

• 대한화학회지
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• 제10권4호
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• pp.166-174
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• 1966

cinnamoylated photosensitive polymer의 광증감 경화반응기구를 반응속도론적으로 연구했다. Cinnamic acid(C)와 증감제(S)의 first excited singlet and lowest triplet energy level diagram과 증감제의 농도증가에 따른 sensitivity의 포화 등의 사실로부터 이 반응의 주요과정은 C와 S의 광 energy흡수에 의한 $C^{*(1)}$ 및 $S^{*(1)}$로의 여기, $S^{*(1)}{\to}S^{*(3)}$ intersystem crossing, S의 excimer 형성, $S^{*(3)}{\to}C^{*(3)}$ energy transfer 그리고 $C^{*(3)}$와 C의 termination 등임을 가정하고 다음 반응속도를 구했다. $-\frac{d[C]}{dt} = \frac{K_1[C]}{K_2 + [C]}[\frac{I^c_{abs}}{K_3 + [S]} + \frac{K_4[C]}{(K_5 + [C])(K_6 + [S])}(I^s_{abs} + \frac{K_7I^c_{abs}[S]}{K_8 + [S]})]$ $I^c_{abs}$와 $I^s_{abs}$ ;C 및 S의 광흡수율 $K_n$;상수 적외선 흡수스펙트럼 분석의 결과, Cinnamoyl 에스테르화도와 sensitivity의 관계 및 증감제의 농도와 sensitivity의 관계에 대하여 발표된 실험 data는 윗식을 만족시키므로 가정한 반응기구에 대한 뒷받침을 얻었다.

• 한국전기전자재료학회논문지
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• 제27권4호
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• pp.232-237
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• 2014

We have fabricated white organic light-emitting diodes (OLEDs) by co-doping of red and blue phosphorescent guest emitters into the single host layer. Tris(2-phenyl-1-quinoline) iridium(III) [$Ir(phq)_3$] and iridium(III)bis[(4,6-di-fluorophenyl)-pyridinato-$N,C^{2^{\prime}}$]picolinate (FIrpic) were used as red and blue dopants, respectively. The effects of dopant concentration on the emission, carrier conduction and external quantum efficiency characteristics of the devices were investigated. The emissions on the guest emitters were attributed to the energy transfer to the guest emitters and direct excitation by trapping of the carriers on the guest molecules. The white OLED with 5% FIrpic and 2% $Ir(phq)_3$ exhibited a maximum external quantum efficiency of 19.9% and a maximum current efficiency of 45.2 cd/A.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.415.2-415.2
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• 2014

Cost-effective, robust devices for solid-state lighting industry that converts electricity to light revolutionize the current lighting industry. Phosphor materials used in these devices should be synthesized in a low-cost and effective method for use in WLEDs. In this presentation, the synthesis of Eu3+ ions doped BaMoO4 phosphor samples by a facile synthesis process for red component of WLEDs will be shown. The tetragonal phase of the host lattice was substantiated by the X-ray diffraction patterns. The morphological studies were carried out by using a field-emission scanning electron microscope and transmission electron microscope. These confirmed the formation of a shuttle like particles with perpendicular protrusions in the middle of the particle. The photoluminescence (PL) properties exhibited good emission with a high asymmetry ratio when excited with ultraviolet B wavelengths (~ 280-315 nm). The cathodoluminescence (CL) spectra showed similar results to the PL spectra, indicating the rich red emission. The results suggest that this phosphor is a good material as red region component in the development of tri-band UV excitation based WLEDs.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.141-144
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• 2001

An accurate cross sections set are necessary for the quantitatively understanding and modeling of plasma phenomena. By using the electron swarm method. we determine an accurate electron cross sections set for objective atoms or molecule at low electron energy range. In previous paper, we calculated the electron transport coefficients in pure $CF_4$ molecular gas by using two-term approximation of the Boltzmann equation. And by using this simulation method. we confirmed erroneous calculated results of transport coefficients for $CF_{4}$ molecule treated in this paper having 'C2v symmetry' as $C_{3}H_{8}$ and $C_{3}F_{8}$ which have large vibrational excitation cross sections which may exceed elastic momentum transfer cross section. Therefore, in this paper, we calculated the electron transport coefficients(W and $ND_L$) in pure $CF_4$ gas by using multi-term approximation of the Boltzmann equation by Robson and Ness which was developed at lames-Cook university, and discussed an application and/or validity of the calculation method by comparing the calculated results by two-term and multi-term approximation code.

• International Journal of Automotive Technology
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• 제8권1호
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• pp.67-73
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• 2007

This study analyzes the interior noise that is generated during acceleration of a passenger car in terms of car body structure and panel contribution. According to the transfer method, interior noise is classified into structure-borne noise and air-borne noise. Structure-borne noise is generated when the engine's vibration energy, an excitation source, is transferred to the car body through the engine mount and the driving system and the panel of the car body vibrates. When structure-borne noise resonates in the acoustic cavity of the car interior, acute booming noise is generated. This study describes plans for improving the car body structure and the panel form through a cause analysis of frequency ranges where the sound pressure level of the rear seat relative to the front seat is high. To this end, an analysis of the correlation between body attachment stiffness and acoustic sensitivity as well as a panel sensitive component analysis were conducted through a structural sound field coupled analysis. Through this study, via research on improving the car body structure in terms of reducing rear seat noise, stable performance improvement and light weight design before the proto-car stage can be realized. Reduction of the development period and test car stage is also anticipated.

• Journal of Photoscience
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• 제1권2호
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• pp.95-105
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• 1994

Experiments were carried out to investigate whether P, deficiency in detached 25 mM mannose-feeding led to a decline of the photosynthetic electron transport rates through acidification of the thylakoid lumen. With increasing mannose-feeding time, the maximal CO2 exchange rates and the maximal quantum yields of photosynthesis decreased rapidly up to 6 h by 73% then with little decrease up to 12 h. The ATP/ADP ratio declined by 54% 6 h after the treatment and then recovered to the control level at 12 h. However, the NADPH/NADP~ ratio was not significantly altered by mannose treatment. Electron transport rates of thylakoid membranes isolated from 6 h treated leaves did not change, but they decreased by 30% in 12 h treated leaves. The quenching analysis of Chl fluorescence in mannose-treated leaves revealed that both the fraction of reduced plastoquinone and the degree of acidification of thylakoid lumen remained higher than those of the control. The reduction of PSI in mannose fed leaves was inhibited due to acidification of thylakoid lumen (high qE). The reduction of primary quinone acceptor of PSII was inhibited by mannose feeding. Mannose treatment decreased the efficiency of excitation energy capture by PSII. Fo quenching was induced when treated with mannose more than 6 h, and had a reverse linear correlation with (Fv)m/Fm ratio. These results suggest that Pi deficiency in Chinese cabbage leaves reduce photosynthetic electron transport rates by diminishing both PSII function and electron transfer from PSII to PSI through acidification ofthylakoid lumen, which in turn induce the modification of photosynthetic apparatus probably through protein (de)phosphorylation.