• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4642-4646
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• 2023

The Tb³⁺ or Eu³⁺-doped Lu₂Gd₁Ga₂Al₃O₁₂ phosphor were fabricated by funace at 1500 ℃ for 12 h using a solid state reaction. The XRD (X-ray diffraction_Panalytical X'Pert Pro) and FE-SEM (field emission scanning electron microscope) are measured to confirm the crystalline structure and surface morphology of the phosphor. The Tb³⁺-doped Lu₂Gd₁Ga₂Al₃O₁₂ phosphor emits the lights in 470~650 nm wavelength range due to transitions from ⁵D₄ to ⁷F_j. Therefore, it shows the green region in the CIE chromaticity diagram under both UV and X-rays excitations. The Eu³⁺-doped Lu₂Gd₁Ga₂Al₃O₁₂ phosphor emits the lights in 550~750 nm wavelength range because of ⁵D_i to ⁷F_j. The emission is confirmed to be in the red region using the CIE chromaticity diagram. The Tb³⁺ or Eu³⁺-doped Lu₂Gd₁Ga₂Al₃O₁₂ phosphor shows the characteristic f-f transition with a long decay time, which is about several milliseconds. They have the high efficiency of light emission for X-ray because of their high effective Z number (Z_eff = 58.5) and density. Therefore, they are very much promising phosphors for X-ray imaging application in medical fields.

• Journal of the Korean Chemical Society
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• v.42 no.3
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• pp.285-291
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• 1998

Methods to determine EU(Ⅲ) ion in aqueous solution by fluorescence spectrometry based upon the ligand sensitized fluorescence of Eu(Ⅲ)-terephthalic acid (TPA) complex ion have been studied. The effects of excitation wavelength, pH, concentration of TPA and emission wavelength on the fluorescence intensity were investigated. The fluorescence intensity of the Eu(Ⅲ) complex ion was further increased with addition of trioctylphosphine oxide (TOPO). In this case Triton X-100 was used to dissolve TOPO in aqueous solution. The calibration curve for Eu(Ⅲ) was linear over the range from $1.0{\times}10^{-6}M\;to\;4.0{\times}10^{-4}M$ and the detection limit was $1.0{\times}10^{-6}M$ under the experimental conditions of 256 nm, 5.6, $3.5{\times}10^{-4}$M$ and 615 nm for excitation wavelength, pH, concentration of TPA and emission wavelength, respectively. When TOPO was added to the Eu(Ⅲ)-TPA system, the concentration range of linear response and the detection limit were $1.0 {\times}10^{-9}M\;to\;1.0{\times}10^{-4}M,\;1.0{\times}10^{-7}M,$ respectively under the experimental conditions of 284 nm, 4.4 and $1.0{\times} 10^{-4}M$ for excitation wavelength, pH and concentration of TOPO, respectively. Effects of interferences from various cations for the determination of Eu(Ⅲ) ion were also investigated.

• Korean Journal of Metals and Materials
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• v.49 no.9
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• pp.732-738
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• 2011

Silicon oxide thin films were deposited by using a plasma-enhanced chemical-vapor deposition technique to investigate the light emission properties. The photoluminescence characteristics were divided into two categories along the relative ratio of the flow rates of $SiH_4$ and $N_2O$ source gases, which show light emission in the broad/visible range and a light emission peak at 380 nm. We attribute the broad/visible light emission and the light emission peak to the quantum confinement effect of nanocrystalline silicon and the Si=O defects, respectively. Changes in the photoluminescence spectra were observed after the post-annealing processes. The photoluminescence spectra of the broad light emission in the visible range shifted to the long wavelength and were saturated above an annealing temperature of $900^{\circ}C$ or after 1 hour annealing at $970^{\circ}C$. However, the position of the light emission peak at 380 nm did not change at all after the post-annealing processes. The light emission intensities at 380 nm initially increased, and decreased at annealing temperatures above $700^{\circ}C$ or after 1 hour annealing at $700^{\circ}C$. The photoluminescence behaviors after the annealing processes can be explained bythe size change of the nanocrystalline silicon and the density change of Si=O defect in the films, respectively. These results support the possibility of using a silicon-based light source for Si-optoelectronic integrated circuits and/or display devices.

• Electrical & Electronic Materials
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• v.8 no.3
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• pp.272-277
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• 1995

We report the properties of optically pumped stimulated emission at room temperature (RT) from column-III nitride semiconductors of GaN, AlGaN/GaN double heterostructure (DH) and AlGaN/GaInN DH which prepared on a sapphire substrate using an AIN buffer-layer by the nietalorganic vapor phase epitaxy (MOVPE) method. The peak wavelength of the stimulated emission at RT from AIGaN/GaN DH is 369nm and the threshold of excitation pumping power density (P$\_$th/) is about 84kW/cm$\^$2/, and they from AlGaN/GaInN DH are 402nm and 130kW/cm$\^$2/ at the pumping power density of 200kW/cm$\^$2/, respectively. The P$\_$th/ of AIGaN/GaN and AlGaN/GaInN DHs are lower than the single layers of GaN and GaInN due to optical confinement within the active layers of GaN and GaInN, respectively.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.220-222
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• 2005

We can classify two cases in a way to observe an atom of gas state or a molecule using the laser. First case is way to use dispersion phenomenon like Rayleigh scattering, Thomson scattering, Mie scattering, Raman Scattering. And Second case is a way to use change phenomenon like a LAS (Laser Absorption Spectroscopy), LIF (Laser Induced Fluorescent). In this paper, we have measured the meta-stable density and the distribution by using a LAS method in Xe discharge lamp. The laser absorption spectroscopy (LAS) is useful to investigate the behavior of such species. The xenon atoms in the $1S_4$ and $1S_5$ generate excited $Xe^*$(147nm) and $Xe_{2}^*$(173nm) dimers in Xe plasma. It is found that the intensity of VUV 147nm emission is proportional to that of the IR 828nm emission, and the VUV 173nm emission is roughly proportional to that of the IR 823nm emission. The laser is used CW laser that consist of AlGaAs semiconductor and energy level is used 823.16nm wavelength. We measured signal of monochrometer from the lamp center while will change a discharge electric current by 6mA in 3mA and calculated meta-stable state density of a xenon atom through a measured value.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.6
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• pp.456-461
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• 2012

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 red/blue, blue/red and red/blue/red emitting layer (EML) structures were fabricated using a host-dopant system. In case of white PHOLEDs with red/blue structure, the best efficiency was obtained at a structure of red (15 nm)/blue (15 nm). But the emission color was blue-shifted white. In case of white PHOLEDs with blue/red structure, the better color purity and efficiency were observed at a blue (29 nm)/red (1 nm) structure. For additional improvement of color purity in white PHOLEDs with blue (29 nm)/red (1 nm) EMLs, we fabricated white PHOLEDs with red (1 nm)/blue (28 nm)/red (1 nm) structure. The current efficiency, external quantum efficiency, and CIE (x, y) coordinate were 27.2 cd/A, 15.1%, and (0.382, 0.369) at 1,000 $cd/m^2$, respectively.

• Korean Journal of Materials Research
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• v.11 no.9
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• pp.759-762
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• 2001

Mg$_2$SnO$_4$having an inverse spinel structure was selected as a new host material of $Mn^{2+}$ activator. The luminescence of the $Mg_2$SnO$_4$:Mn phosphor prepared by the solid-state reaction were investigated under ultraviolet and low-voltage electron excitation. The Mn-doped magnesium tin oxide exhibited strong green emission with the spectrum centered at 500nm wavelength. It was explained that the green emission in $Mg_2$SnO$_4$:Mn phosphor is due to energy transfer from $^4T_1to ^6A_1\;of\; Mn^{2+}$ ion at tetrahedral site in the spinel structure. The optimum concentration of $Mn^{2+}$/ion exhibiting maximum emission intensity by the low-voltage electron excitation was 0.6mol%. ？

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.5
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• pp.432-436
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• 2006

The $ZnGa_2O_4$ and Mn, Cr-doped $ZnGa_2O_4$ Phosphors were synthesized through conventional solid state reactions. The XRD patterns show that the $ZnGa_2O_4$ has a (3 1 1) main peak and a spinel phase. The emission wavelength of $ZnGa_2O_4$ showed main peak of 420 nm and maximum intensity at the sintering temperature of $1100^{\circ}C$. In the crystalline $ZnGa_2O_4$, the Mn shows green emission (510 nm, $^4T_1-^6A_1$) with a quenching concentration of 0.6 mol%, and the Cr shows red emission (705 nm, $^4T_2-^4A_2$) with a quenching concentration of 2 mol%. These results indicate that $ZnGa_2O_4$ Phosphors hold promise for potential applications in field emission display devices with high brightness operating in full color regions.

• Journal of the Korean Chemical Society
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• v.55 no.2
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• pp.204-207
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• 2011

A particle counting system that can also provide sensitive, specific chemical information, while consuming very less power, occupying less space, and being inexpensive has been developed. This system uses a microwave plasma torch (MPT) as the excitation source for atomic emission spectrometry (AES). Emission from a single particle can be detected, and the wavelength at which the emission is observed indicates the elements present in the particle. It is believed that correlating the particle size and emission intensity will allow us to estimate the particle size in addition to abovementioned capabilities of the system. In the long term, this system can be made field-portable, so that it can be used in atmospheric aerosol monitoring applications, which require real-time detection and characterization of particles at low concentrations.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.11
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• pp.943-949
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• 2000

In this paper, the single and double heterostructure organic light-emitting devices(OLEDs) were fabricated. The single heterostructure OLED(TYPE 1) is consisted of TPD as a HTL(hole transfer layer) and Alq$_3$as an EML(emitting layer). The double heterostructure OLED(TYPE 2) is consisted of TPD as a HTL, Alq$_3$as an EML and PBD as an ETL(electron transfer layer). The another double heterostructure OLED(TYPE 3) is consisted of TPD as a HTL, PBD as an EML and Alq$_3$as an ETL. We obtained a strong green emission device with maximum EL emission wavelength 500nm in TYPE 3. When the applied voltage was 12V, the emission luminescence was 120.9cd/㎡. The chromaticity index of TYPE 3 was x=0.29, y=0.50. In the characteristic plot of current-voltage, TYPE 3 device was turned on at 6.9V. This voltage was a fairly low turn-on voltage. TYPE 1 and 2 device were turned on at 10V and 8.9V respectively. These types showed no good properties over that of TYPE 3.