• Journal of Sensor Science and Technology
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• v.12 no.3
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• pp.139-148
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• 2003

$LiPO_3$ glass scintillators were fabricated, and lanthanides(except Pm) oxides or chlorides were used as an activator. For the fabrication of $LiPO_3$ glasses, optimum heating conditions were obtained, and the photoluminescence of the glasses was measured by the monochromator. For the best transparency of the glass samples, optimum heating temperature and time are $950^{\circ}C$ and 90 min, respectively. It was found that Pr, Nd, Gd, Ho, Er, Tm, Yb and Lu do not work as activator; emission spectrums of samples with them were equal to those of samples without activators. In the case of samples with Europium, the peaks of emission spectrum of $Eu^{2+}$ and $Eu^{3+}$ were 420 nm and 620 nm respectively. And samples with $Ce^{3+}$ were about 380 nm, and $Tb^{3+}$ were about 550 nm. Glass scintillators with $Be^{3+}$, $Eu^{2+}$, and $Ce^{3+}$ were found to be more applicable to neutron detection. The result of neutron detection by Ra-Be sources showed that $Ce^{3+}$ was found to be the best activator of $LiPO_3$.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.449-449
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• 2010

유기발광소자(organic light-emitting diodes, OLEDs)는 저공정비용, 경량화, 가용성 및 대면적화 등의 장점으로 조명 분야와 디스플레이 분야로의 응용 가능성으로 인해 크게 주목을 받아 왔다. 이러한 OLED 소자의 고효율, 고휘도 및 저소비전력 등을 구현하기 위해서는 전극으로부터 전하 주입 층으로 효율적인 전하 주입이 요구된다. 즉, 각 전극의 폐르미 준위로부터 전하 전도준위대로의 전하주입 장벽이 없어야 한다. 본 연구에서는 홀 주입장벽이 없는 정공주입 층으로 $MoO_x$(molybdenum oxide)가 도핑된 NPB(N, N'-diphenyl-N, N'-bis(1-naphthyl)-1,1'-biphenyl-4,4'-diamine) 층을 사용하여 hole-only 소자를 제작하고 전류-전압 특성을 통해 양극으로부터 홀주입 층으로의 hole-ohmic 특성을 고찰했다. 또한, 전자 주입장벽이 없는 전자주입 층으로 $C_{60}$(fullerene)/LiF(lithum fluoride)의 이종 층을 사용하여 electron-only 소자를 제작하고 음극으로부터 전자주입 층으로의 전자 ohmic 특성을 조사했다. 또한, 전극으로부터 전하주입 층으로 ohmic 특성을 더 자세히 이해하기 위하여 전하주입 층의 자외선 광방출 스펙트럼(ultraviolet photoemission spectra)을 조사했다. 한편, glass/ITO/$MoO_x$-doped NPB (x%: x=0,25, 50 및 75; 5nm)/NPB (63nm)/$Alq_3$ (37nm)/$C_{60}$ (5nm)/LiF (1nm)/Al (100nm)로 구성된 all-ohmic OLED 소자의 발광특성은 $MoO_x$의 도핑 농도가 25%이상일 때 최적의 특성을 보여줬다. 이러한 현상은 정공주입 층에서 p형 도핑 농도의 증가에 따른 정공 농도의 증가에 기인한다. 또한 $MoO_x$의 도핑 농도의 증가에 따라 정공주입 층의 new gap state와 전극의 페르미 준위의 pinning에 기인한다. 25%의 $MoO_x$을 가진 OLED소자는 7.2V의 낮은 전압에서 $58300 cd/m^2$의 높은 휘도를 보여줬다.

• Journal of the Korean Vacuum Society
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• v.20 no.2
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• pp.135-140
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• 2011

By investigating photoluminescence (PL) spectra (20 K) of undoped and Be-doped p-type GaSb/GaAs epilayers, the origin has been analyzed by the change due to doping density. We have observed that the PL peak shifts to higher energy and the full-width half-maximum (FWHM) decreases with increasing the doping density below ${\sim}10^{17}cm^{-3}$, contrasted to shift to low energy and increasing FWHM above the density of ${\sim}10^{17}cm^{-3}$. From the variation of the integrated PL intensities of three peaks dissolved by Gaussian fit, it has been analyzed that, as the density increases, the $Be[Be_{Ga}]$ acceptor level (0.794 eV) reduces, whereas the intrinsic defect of $A[Ga_{Sb}]$ (0.778 eV) enhances together with a new $Be^*$ level (0.787 eV) locating between A and Be. We have discussed that it is due to coexistence of the Be acceptor level (${\Delta}E=16meV$) and the complex level (${\Delta}E=23meV$), $Be^*[Ga_{Sb}-Be_{Ga}]$combined by Be and A, in Be-doped p-GaSb, and that the level density of $Be[Be_{Ga}]$ may be reduced above ${\sim}10^{17}cm^{-3}$.

• Journal of Adhesion and Interface
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• v.17 no.4
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• pp.141-148
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• 2016

In this work, mesoporous silica (SBA-15) was synthesized via self-assembly process using triblock copolymer ($PEO_{20}PPO_{70}PEO_{20}$, P123) as template and tetraethyl orthosilicate (TEOS) as silica source under acidic condition. SBA-15 have high surface area ($704m^2g^{-1}$) and uniform pore size (8.4 nm) with well-ordered hexagonal mesostructure. Spiropyran-functionalized SBA-15 (Spiropyran-SBA-15) was synthesized via post-synthesis process using 3-(triethoxysilyl)propyl isocyanate (TESPI) and 1-(2-Hydroxyethyl)-3,3-dimethy-lindolino-6'-nitrobenzopyrylo-spiran (HDINS). Spiropyran-SBA-15 was produced with hexagonal array of mesopores without damage of mesostructre. Surface area and pore size of Spiropyran-SBA-15 were $651m^2g^{-1}$ and 8.0 nm, respectively. Optochemical properties of Spiropyran-SBA-15 was studied with chemical vapors such as EtOH, THF, $CHCl_3$, Acetone and HCl. Main peaks of photofluorescence of Spiropyran-SBA-15 exhibited blue shift in the range of 603.4~592.1 nm after exposure under EtOH, THF, $CHCl_3$, and Acetone vapors. Normalized peak intensities decreased in the range of 0.8~0.3. The main peak of photofluorescence of Spiropyran-SBA-15 showed significant blue shift of 592.1 nm after exposure under HCl vapor, while normalized peak intensity decreased to 0.1.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.107-107
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• 2010

ZnO는 상온에서 에너지 밴드갭이 3.37 eV 이고 엑시톤 속박에너지가 60 meV 인 넓은 에너지 띠를 가진 반도체이다. ZnO 반도체는 고에너지 영역에서 광투과율 및 에너지 수집율이 큰 특성을 가지고 있기 때문에 단파장 영역에서 작동하는 발광 다이오드나 반도체레이저 소자 응용에 사용되고 있다. 이와 더불어 액정디스플레이, 유기발광소자 및 태양전지에서 투명 산화물 전극으로 많은 응용이 되고 있다. 본 연구에서는 p-type Si 기판 위에 ZnO 나노입자 형성과 구조적 성질과 전자적 성질에 대하여 조사하였다. ZnO 나노입자를 형성하기 위해 ethanol에 zinc acetate dehydrate (5 wt%)을 적절히 분산시킨 $Zn(CH_3COO)_2H_2O\;+\;CH_3OH$ 용액을 스핀 코팅하여 산소 분위기에서 각각 $300^{\circ}C$, $500^{\circ}C$, $700^{\circ}C$ 및 $900^{\circ}C$로 각각 2시간 동안 열처리 하였다. X-ray 회절 실험 결과는 열처리 온도에 관계없이 ZnO (0001)의 피크가 관측되었다. 원자힘 현미경 이미지상으로 열처리 온도에 따른 ZnO 나노입자의 표면상태의 변화와 나노입자의 크기의 변화를 확인하였다. X-ray 광전자 분광 스펙트럼 결과는 Zn $2p_{3/2}$와 O 1s의 전자상태 스펙트럼을 분석하여 ZnO 나노입자가 형성됨을 보여주었다. 본 연구를 통하여 용액방법을 사용하여 제작된 ZnO 나노입자의 열처리 온도변화에 따른 구조적 성질과 전자적 성질을 이해하는데 도움을 줄 것이다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.3
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• pp.109-114
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• 2008

Novel green long persistent phosphors of $CaZrO_3$ : $HO_{3+}$ have been synthesized at high temperature with weak reduction atmosphere by traditional solid state reaction method. The role of $H_3BO_3$ as flux and the suitable concentration of Ho as activator on the $CaZrO_3$ : $HO_{3+}$ long persistent phosphors has been investigated. Crystals of $HO_{3+}$ doped $CaZrO_3$ long persistent phosphores were characterized by fluorescence spectrophotometer and photoluminescence (PL). The main emission spectra of 546 nm peak was revealed through synthesizing at high temperature in $N_2$ gas atmosphere. The after glow emission spectra of $CaZrO_3$ : $HO_{3+}$ long persistent phosphores arise at 546 nm peak of narrow range. because that revealed pure green color. Green long persistent phosphors have been observed in the system for over 5 h after UV irradiation (254 nm). The main emission peak was ascribed to $HO_{3+}$ ions transition from $^5F_4$, $^5S_2{\to}^5I_3$, and the after glow may be ascribed to the trap centers in the $CaZrO_3$ host lattice.

• Korean Journal of Optics and Photonics
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• v.24 no.3
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• pp.135-142
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• 2013

Two white light emitting diodes(LEDs) were fabricated by using two kinds of yellow phosphor, YAG:Ce and $(Sr,Ba)_2SiO4:Eu$, and their spectroscopic properties were analyzed as a function of temperature from room temperature to $80^{\circ}C$. The asymmetric double sigmoidal function was applied to both blue and yellow peaks of the emitting spectrum to obtain the center wavelength, the amplitude, the half width, and the skewness parameters. According to this analysis, the center wavelength of the blue peak shifted to longer wavelength while that of the yellow peak shifted to shorter wavelength. In addition, some of the skewness parameters were found to increase upon heating, which indicates that spectrum asymmetry becomes enhanced at higher temperatures. The changes in the color coordinates and the luminous efficacy were larger for the case of silicate-based white LED. These results suggest that the silicate-based white LED is inferior to the YAG-based white LED from the viewpoint of color stability, efficacy and color rendering index.

• Journal of the Korean Chemical Society
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• v.44 no.5
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• pp.453-459
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• 2000

FED has deserved an intensive attentioD as a new flat panel display. The present investigationaims at undemtanding the photoluminescence and cathodoluminescent properties of hGaO$_3$: $Eu^{3+}$ phosphor bytaking into account the possibility that this phosphor could be applied for FED. In onler to investigate on.sucha detailed behavior; 8everM experimental skil18 Je conducted to the LaGaO$_3$:$Eu^{3+}$ phosphoL The excimtion srectrum artd emission spectmn were rnezsured in the UV range and then decay curve of $^5D_0$+$^7F_j$transitions\vas examined. The decay behavior of $^5D_0$ emission was anMyzed by a newly Iuoposed cross-relaxation mech-ani8In in asswiation with inteFwnter di1ffision (or migration). The cross-mlaxation from $^5D_0$ to CTB (Cha'geTransfer Band) wuld be a quite retsonable by considering the excitation spectrum. It could be also found thatthe quenching type was changed from ditfrsion controlled process to the direct quenching process -s inJeasing $Eu^{3+}$ oncntration.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.41.1-41.1
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• 2011

본 연구에서는 MOCVD법으로 사파이어 기판위에 u-GaN를 성장한 후 Mg을 도핑시켜 p-GaN를 성장하고, RF 스퍼터를 이용하여 n-ZnO를 도포하여 n-ZnO/p-GaN 이종접합을 형성한 후 진공증착기를 이용하여 Au/Ni를 증착시켜 발광다이오드(LED)를 제작하고 전기 광학적 특성을 조사하였다. 두께가 500 nm인 u-GaN 위에 성장된 p-GaN의 운반자 농도는 $1.68{\times}10^{17}\;cm^{-3}$ 이었다. 그리고 150, 300 nm 두께의 p-GaN에 대하여 측정된 DXRD 반치폭은 각각 450 arcsec, 396 arcsec 이었고, 상온에서 2.8~3.0 eV 영역에서 Mg 억셉터와 관련된 광루미네센스가 검출되었다. RF 스퍼터링에 의해 0.7 nm/min의 속도로 증착된 n-ZnO 박막은 증착 두께에 따라 비저항이 27.7 $m{\Omega}{\cdot}cm$ 에서 6.85 $m{\Omega}{\cdot}cm$ 까지 감소하였다. 그리고 n-ZnO 박막은 (0002)면으로 우선 배향되었으며, 상온에서 에너지갭 관련된 광루미네센스가 3.25 eV 부근에서 주되게 검출되었다. n-ZnO/p-GaN 이종접합 LED의 전류전압 특성곡선은 다이오드 방정식에 만족하는 특성을 나타내었다. 다이오드 지수는 3 V 이하 영역에서 1.64, 3~5 V 영역에서 0.85이었다. 그리고 5 V 이상 영역에서 공간전하의 제한을 받았으며, 다이오드 지수는 3.36이었다. 한편, 역방향 전류전압 특성은 p-GaN 박막의 두께에 영향을 받았으며, p-GaN 박막의 두께가 150, 300 nm 일 때 각각의 누설 전류는 $1.3{\times}10^{-3}$ mA와 $8.6{\times}10^{-5}$ mA 이었다. 상온에서 측정된 EL 스펙트럼의 주된 발광피크는 430 nm이었고, 반치폭은 49.5 nm이었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.5
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• pp.228-232
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• 2021

Ca_1-xZrO₃:xPr phosphor with perovskite structure was successfully synthesized by using skull melting method. The crystal structure, morphology and optical properties of synthesized phosphor were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet fluorescence reaction and photoluminescence. The XRD results indicated that single crystals of CaZrO₃:Pr³⁺ belongs to orthorhombic perovskite system. The synthesized phosphor could be excited by UV light (254 nm) and the emission spectra results indicated that green luminescence of CaZrO₃:Pr³⁺ due to charge transfer transition ³P₀ → ³H₄, ³P₁ → ³H₅ and ³P₀ → ³H₅ at 506, 536 and 548 nm was dominant.