• 한국결정성장학회지
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• 제15권4호
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• pp.145-151
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• 2005

어두운 적색을 나타내는 아프리카산 천연루비의 색상개선을 열처리법과 수열처리법을 이용하여 행한 결과, 열처리법은 색상이 떨어지는 역효과가 발생하였다. 그러나 수열처리법의 경우에는 색상과 투명도가 향상되었다. 아프리카산 천연루비의 색상개선에 대한 수열처리 조건은 다음과 같다. 즉, 수열용매 1M $Na_2CO_3-0.9M\;K_2CO_3$, 반응온도: $450^{\circ}C$, 반응 시간: 48hrs, 충전율: $30\%$, 압력: 375atm이었다. 이와 같은 조건에서 얻어진 루비의 특성을 평가한 결과, ICP/MS와 XRF 분석결과로부터 수열처리 후 $Cr^{3+},\;Fe^{3+},\;Ti^{4+}$ 등의 함량이 수열처리 전의 루비에 비해 감소됨을 알 수 있었으며, 이로 인하여 적색이 밝아지는 것을 색차계 분석결과로부터 알았다. 이 결과는 수열처리 전과 비교하였을 때 $Cr^{3+}$ 이온의 전자전이에 의해 발생되는 발광피크의 강도가 수열처리 후 감소한 PL분석결과와 잘 일치하였다.

• 한국재료학회지
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• 제23권3호
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• pp.161-167
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• 2013

The ZnO thin films were grown on GaN template substrates by RF magnetron sputtering at different RF powers and n-ZnO/p-GaN heterojunction LEDs were fabricated to investigate the effect of the RF power on the characteristics of the n-ZnO/p-GaN LEDs. For the growth of the ZnO thin films, the substrate temperature was kept constant at $200^{\circ}C$ and the RF power was varied within the range of 200 to 500W at different growth times to deposit films of 100 nm thick. The electrical, optical and structural properties of ZnO thin films were investigated by ellipsometry, X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) and by assessing the Hall effect. The characteristics of the n-ZnO/p-GaN LEDs were evaluated by current-voltage (I-V) and electroluminescence (EL) measurements. ZnO thin films were grown with a preferred c-axis orientation along the (0002) plane. The XRD peaks shifted to low angles and the surface roughness became non-uniform with an increase in the RF power. Also, the PL emission peak was red-shifted. The carrier density and the mobility decreased with the RF power. For the n-ZnO/p-GaN LED, the forward current at 20 V decreased and the threshold voltage increased with the RF power. The EL emission peak was observed at approximately 435 nm and the luminescence intensity decreased. Consequently, the crystallinity of the ZnO thin films grown with RF sputtering powers were improved. However, excess Zn affected the structural, electrical and optical properties of the ZnO thin films when the optimal RF power was exceeded. This excess RF power will degrade the characteristics of light emitting devices.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.144-144
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• 2008

Blue light emitting diode structures consisting of the InGaN/GaN multiple quantum wells were grown by metalorganic chemical vapor deposition at different growth temperatures for the p-GaN contact layers and the influence of growth temperature on the emission and microstructural properties was investigated. The I-V and electroluminescence measurements showed that the sample with a p-GaN layer grown at $1084^{\circ}C$ had a lower electrical turn-on voltage and series resistance, andenhanced output power despite the low photoluminescence intensity. Transmission electron microscopy (TEM) revealed that the intense electro luminescence was due to the formation of a p-GaN layer with an even distribution of Mg dopants, which was confirmed by TEM image contrast and strain evaluations. These results suggest that the growth temperature should be optimized carefully to ensurethe homogeneous distribution of Mg as well as the total Mg contents in the growth of the p-type layer.

• 한국결정학회지
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• 제13권1호
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• pp.25-30
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• 2002

M/sub 1-x/Na/sub 2x/Al₂(BO₃)₂O (M = Ca and Sr) 고용체계는 치환형과 틈새형 고용체를 동시에 갖는다. 이상의 고용체계 물질에 첨가된 발광원자의 에너지 전이는 발광원자, Eu 주위의 대칭성에 깊은 관계가 있다 Eu/sup 3+/ 이온의 경우, Eu/sup 3+/ 이온의 주변 대청성에 따라서 매우 밝고 효율적인 발광성 불순물이 될 수 있기 때문에 구조와 연계한 연구가 가능하다. Eu/sup 3+/: Ca/sub 1-x/Na/sub 2x/Al₂(BO₃)₂O 고용체계의 Na원자 양이 증가함에 따라 Eu3+ 이온의 대칭성이 낮아진다. CaAl₂(BO₃)₂O 화합물은 Ca 원자 중심의 팔면체 구조를 갖기 때문에, 조성비 x의 증가와 함께, 화합물의 낮은 대청성에 의해서 Eu/sup 3+/:Ca/sub 1-x/Na/sub 2x/Al₂(BO₃)₂O 고용체계의 /sup 5/D/sub 0/→/sup 7/F₁(590 nm) 전이의 상대적인 세기가 감소한다. 그러한 또 다른 예는 비대칭성 물질인 Eu/sup 3+/:SrAl₂(BO₃)₂O 화합물에서도 찾아 볼 수 있었다.

• Preventive Nutrition and Food Science
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• 제9권4호
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• pp.317-323
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• 2004

Photostimulated Luminescence (PSL), Electron Spin Resonance (ESR) and Thermoluminescence (TL) analysis were conducted to detect irradiation treatment of imported whole and ground spices. The screening by PSL detected no irradiation treatment, except un the ground thyme and bay leaves which exhibited photon counts in the intermediate level. Irradiation of the two spices was detected after irradiating them at 1.0, 3.0, 5.0 and 10.0 kGy, and then subjecting them to PSL analysis, which resulted in the significantly low photons of non-irradiated spices compared to that at 1.0 kGy, indicating that the photon counts varied depending on the amount of inorganic mineral debris in the spices. To confirm a successful detection by using PSL, ESR and TL methods, some spices were selected, irradiated at 5.0 and 10.0 kGy, and subjected to the detection methods. PSL identified the irradiated spices except the cassia, which showed very weak PSL sensitivity, but was identified by ESR analysis. Also, the ESR and TL exhibited the typical signals induced by irradiation treatment and were able to successfully detect all of the irradiated spices. In addition, we found a positive correlation between the intensity of ESR and TL signals and irradiation doses.

• 한국전기전자재료학회논문지
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• 제29권9호
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• pp.546-551
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• 2016

$SrSnO_3:Tb^{3+}$ phosphor thin films were prepared on sapphire and quartz substrates in the growth temperature range of $100{\sim}400^{\circ}C$ by using the radio frequency magnetron sputtering deposition. The resulting $SrSnO_3:Tb^{3+}$ thin films were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible-infrared spectrophotometer, and photoluminescence spectrometer. The results indicated that the morphology, optical transmittance, band gap energy, and luminescence intensity of the phosphor thin films significantly depended on the growth temperature. All the thin films, regardless of the type of substrate, showed an amorphous behavior. As for the thin films deposited on sapphire substrate, the maximum crystallite size was obtained at a growth temperature of $400^{\circ}C$ and the strongest emission was green at 544 nm arising from the $^5D_4{\rightarrow}^7F_5$ transition of Tb3+. The average optical transmittance for all the thin films grown on sapphire and quartz substrates was decreased as the growth temperature increased from 100 to $400^{\circ}C$. The results suggest that the optimum growth temperatures for depositing highly-luminescent $SrSnO_3:Tb^{3+}$ phosphor thin films on sapphire and quartz substrates are 400 and $300^{\circ}C$, respectively.

• 한국진공학회지
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• 제20권3호
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• pp.176-181
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• 2011

$Y_{1-x}BO_3:Ce_x^{3+}$ 세라믹 청색 형광체를 고상 반응법을 사용하여 $Ce^{3+}$ 이온의 농도를 변화시키면서 합성하였다. 청색 형광체의 결정 구조, 표면 형상과 광학 특성은 각각 X-선 회절 장치(XRD), 주사전자현미경, 광여기 및 발광 분광기를 사용하여 측정하였다. XRD 결과로부터 합성된 모든 형광체 분말의 주 피크는 (401)와 ($31\bar{2}$)면에서 발생한 회절 신호이었다. 광학 특성의 경우에, $Ce^{3+}$ 이온의 농도비가 0.10 mol일 때 여기 스펙트럼은 243 nm에서 발생하였고, 469 nm에 피크를 갖는 최대의 청색 형광 스펙트럼이 관측되었다.

• 한국재료학회지
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• 제18권2호
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• pp.84-91
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• 2008

The effects of the deposition and annealing temperature on the structural, electrical and optical properties of Ag doped ZnO (ZnO : Ag) thin films were investigated. All of the films were deposited with a 2wt% $Ag_2O-doped$ ZnO target using an e-beam evaporator. The substrate temperature varied from room temperature (RT) to $250^{\circ}C$. An undoped ZnO thin film was also fabricated at $150^{\circ}C$ as a reference. The as-grown films were annealed in temperatures ranging from 350 to $650^{\circ}C$ for 5 h in air. The Ag content in the film decreased as the deposition and the post-annealing temperature increased due to the evaporation of the Ag in the film. During the annealing process, grain growth occurred, as confirmed from XRD and SEM results. The as-grown film deposited at RT showed n-type conduction; however, the films deposited at higher temperatures showed p-type conduction. The films fabricated at $150^{\circ}C$ revealed the highest hole concentration of $3.98{\times}1019\;cm^{-3}$ and a resistivity of $0.347\;{\Omega}{\cdot}cm$. The RT PL spectra of the as-grown ZnO : Ag films exhibited very weak emission intensity compared to undoped ZnO; moreover, the emission intensities became stronger as the annealing temperature increased with two main emission bands of near band-edge UV and defect-related green luminescence exhibited. The film deposited at $150^{\circ}C$ and annealed at $350^{\circ}C$ exhibited the lowest value of $I_{vis}/I_{uv}$ of 0.05.

• 대한금속재료학회지
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• 제49권4호
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• pp.348-354
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• 2011

Long-lasting brightness $Sr_{4}Al_{14}O_{25}$ : $Eu^{2+}$, $Dy^{3+}$, $Ag^{+}$ phosphor was synthesized by modified solid state reaction and its photoluminescence was investigated. $Sr(NO_3)_{2}$ and $Al(NO_3)_3{\cdot}9H_{2}O$ as starting materials, and $B_{2}O_{3}$ as a flux were mixed with $Eu_{2}O_{3}$ as an activator, $Dy_{2}O_{3}$ as a coactivator, and $AgNO_{3}$ as a charge compensator. The crystalline of target powder showed a single-phase $Sr_{4}Al_{14}O_{25}$ by the XRD characterization and the average particle size was about 20-30 ${\mu}m$ from the FE-SEM observation. $Ag^{+}$ ion doping effects (0-0.06 mol) on $Sr_{4}Al_{14}O_{25}:Eu^{2+},\;Dy^{3+},\;Ag^{+}$ phosphor were measured by photoluminescence spectrometer and luminescence meter. The of photoluminescence intensity of the $Sr_{3.64}Al_{14}O_{25}:Eu_{0.11},\;Dy_{0.22},\;Ag_{0.03}$ phosphor was higher than other compositions and afterglow brightness was 0.186 $cd/m^{2}$.

• 한국재료학회지
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• 제32권10호
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• pp.425-428
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• 2022

In this study, Y₃Al₅O₁₂:Eu³⁺ red phosphors were synthesized at different temperatures using a solid state reaction method. The crystal structures, surface and optical properties of the Y₃Al₅O₁₂:Eu³⁺ red phosphors were investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and photoluminescence (PL) analyses. From XRD results, the crystal structure of the Y₃Al₅O₁₂:Eu³⁺ red phosphors was determined to be cubic. The maximum emission spectra were observed for the Y₃Al₅O₁₂:Eu³⁺ red phosphor prepared by annealing for 4h at 1,700 ℃. The 565~590 nm photoluminescent spectra of the Y₃Al₅O₁₂:Eu³⁺ red phosphors is associated with the ⁵D₀ → ⁷F₂ magnetic dipole transition of the Eu³⁺ ions. The intensity of the photoluminescent spectra in the red phosphors is more dominant for the magnetic dipole transition than the electric dipole transition with increasing annealing temperature. The International Commission on Illumination (CIE) coordinates of Y₃Al₅O₁₂:Eu³⁺ red phosphors prepared by 1,700 ℃ annealing temperature are X = 0.5994, Y = 0.3647.