• Nuclear Engineering and Technology
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• 제54권2호
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• pp.429-436
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• 2022

Investigations of retrospective dosimetry have shown that components of mobile phones are suitable as emergency dosimeters in case of radiological incidents. For physical dosimetry, components can be read out using optically stimulated luminescence (OSL), thermoluminescence (TL) and phototransferred thermoluminescence (PTTL) methods to determine the absorbed dose. This paper deals with a feasibility study of display glass from modern mobile phones that are measured by thermally assisted (Ta) optically stimulated luminescence. Violet (VSL, 405 nm) and infrared (IRSL, 850 nm) LEDs were used for optical stimulation and two protocols (Ta-VSL and Ta-IRSL) were tested. The aim was to systematically investigate the luminescence properties, compare the results to blue stimulated Ta-BSL protocol (458 nm) and to develop a robust measurement protocol for the usage as an emergency dosimeter after an incident with ionizing radiation. First, the native signals were measured to calculate the zero dose signal. Next, the reproducibility and dose response of the luminescence signals were analyzed. Finally, the signal stability was tested after the storage of irradiated samples at room temperature. In general, the developed Ta-IRSL and Ta-VSL protocols indicate usability, however, further research is needed to test the potential of a new protocol for physical retrospective dosimetry.

• 한국결정성장학회지
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• 제6권4호
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• pp.564-570
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• 1996

급속 열산화 없이 다공성 실리콘으로부터 적색 및 청색 발광을 관찰할 수 있었다. 묽은 HF 농도에서, 특히 짧은 양극 산화 북식으로제조한 aged 된 다공성 실리콘은 청색band 의 증가를 나타내었다. 상온에서 측정된 발광 decay 시간은 약 100 ps를 나타내었고 20K에서 측정된 값에 비하여 상당히 빠른 값을 지니고 있었다. 청색 광발광 peak 최대값은 액체질소온도에서 청색전이를 나타내지 않았다. 그러나 적색 광발광 band는 77K 에서 적색으로 전이를 하였고 황색을 나타내었다. 적색 발광의 origin은 Si 결정과 연관이 있는 것으로 사료되어지는 한편 청색 발광은 Si결정과 무관한 것으로 생각되어 진다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 학술대회 논문집 전문대학교육위원
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• pp.165-169
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• 2007

Organic EL has been expected to adopt to a new styles of technology that make flat display after Tang & Vanslyke made food electric luminescence device in late 1980s. Their studies based on multi layer structure that consists of emitting layer and carrier transporting layer using proper organic material. In this study we made multi layer device using $Eu(TTA)_3(phen)$ as a luminescence material by PVD and investigate luminous properties of each device. But oxidization of organic layer by ITO, energy walls in both pole interface, contaminations of ITO surface, importance of protecting membrane, diffusive dimming of light to cathode organic layer, these causes of degradations are common facts of a macromolecule and micromolecule. We think these degradation caused by the impact of heat and electro-chemical factor, bulk effect and interface phenomenon, and raise a question.

• 한국전기전자재료학회논문지
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• 제14권1호
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• pp.48-53
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• 2001

The crystal structure of ZnS fabricated by gas-liquid phase reaction was refined by the Rietveld program using X-ray diffraction data. The R-weighted pattern (R$\sub$wp/) of ZnS powder was 10.85%. The fraction of HCP phase was closely related with extra amount of H$_2$S gas. The lattice parameters and crystalline size were changed by the relative ratio of multi-phase. The luminescence property of ZnS:Cu, Al green phosphors prepared by conventional methods was good in the range of 91∼94% and 150∼190${\AA}$, respectively. According to the maximum entropy electron density(MEED) methods, any defects in (001) plane of cubic phase were not found. We suggest that both the Rietveld and maximum entropy density methods may be useful tools for studying luminescence mechanism of other phosphors materials.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권3호
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• pp.125-130
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• 2006

The optical gain and the luminescence of a ZnO quantum well with MgZnO barriers is studied theoretically. We calculated the non-Markovian optical gain and the luminescence for the strained-layer wurtzite quantum well taking into account of the excitonic effects. It is predicted that both optical gain and luminescence are enhanced for the ZnO quantum well when compared with those of InGaN-AlGaN quantum well structure due to the significant reduction of the piezoelectric effects in the ZnO-MgZnO systems.

• 한국전기전자재료학회논문지
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• 제19권5호
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• pp.422-426
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• 2006

[ $Sr_xCa_{(1-x)}TiO_3$ ] red phosphors doped with Pr(0.13 mol%) and Al(0.23 mol%) were synthesized by solid state reaction method. Change of crystal structure occurred in $Sr_xCa_{(1-x)}TiO_3:Pr,Al$ phosphors with increasing value of x. Green and red luminescence were observed from $SrTiO_3:Pr,Al$ phosphors at low temperature. However, only red luminescence in the case of $CaTiO_3:Pr,Al$ phosphors was measured at low temperature. The main cause of green luminescence was explained by the bandgap reduction.

• 한국세라믹학회지
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• 제43권11호
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• pp.743-745
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• 2006

The luminescence properties of $Sr_{1-x}Ba_xTiO_3:Pr$, Al red phosphor for Field Emission Displays (FEDs) have been investigated in powders prepared though solid-state reactions. $Sr_{1-x}Ba_xTiO_3:Pr$, Al red phosphors indicate a higher luminescent intensity, and have been found to have potential for field emission displays. The addition of Ba increased the luminescence intensity at 617 nm by up to 30%. Ba ions are effective in producing the energy transfers from host-to-activator in 4f-5d transitions.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1576-1579
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• 2005

With varying rapid thermal annealing (RTA) temperature, luminescence properties of $Zn_{0.75}Mg_{0.25}S:Mn$ thin film deposited by RF-magnetron sputtering technique were investigated. In this study, $Zn_{0.75}Mg_{0.25}S:Mn$ thin film phosphor showed more red emission than those of the previous studies when annealed around 600 or $650^{\circ}C$. Although all samples were deposited from identical source composition, a main peak wavelength of photoluminescence spectra of $Zn_{0.75}Mg_{0.25}S:Mn$ shifted toward shorter wavelengths depending upon increase of RTA temperature. The same dependence of wavelength on RTA temperature was also observed in cathodoluminescence as well as electroluminescence measurements. It was revealed that the change of the luminescence properties were originated from structural changes in $Zn_{0.75}Mg_{0.25}S:Mn$ thin film phosphor from cubic to hexagonal phases analyze using conventional X-ray pole figure mapping. The phase transition would be the origin of luminescence property changes with respect to RTA temperature.

• 방사성폐기물학회지
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• 제18권4호
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• pp.497-508
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• 2020

In the geochemical field, the chemical speciation of hexavalent uranium (U(VI)) has been widely investigated by performing measurements to determine its luminescence properties, namely the excitation, emission, and lifetime. Of these properties, the excitation has been relatively overlooked in most time-resolved laser fluorescence spectroscopy (TRLFS) studies. In this study, TRLFS and continuous-wave excitation-emission matrix spectroscopy are adopted to characterize the excitation properties of U(VI) surface species that interact with amorphous silica. The luminescence spectra of U(VI) measured from a silica suspension and silica sediment showed very similar spectral shapes with similar lifetime values. In contrast, the excitation spectra of U(VI) measured from these samples were significantly different. The results show that distinctive excitation maxima appeared at approximately 220 and 280 nm for the silica suspension and silica sediment, respectively.

• 한국재료학회지
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• 제28권10호
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• pp.578-582
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• 2018

ZnO crystals with different morphologies are synthesized through thermal evaporation of the mixture of Zn and Cu powder in air at atmospheric pressure. ZnO crystals with wire shape are synthesized when the process is performed at $1,000^{\circ}C$, while tetrapod-shaped ZnO crystals begin to form at $1,100^{\circ}C$. The wire-shaped ZnO crystals form even at $1,000^{\circ}C$, indicating that Cu acts as a reducing agent. As the temperature increases to $1,200^{\circ}C$, a large quantity of tetrapod-shaped ZnO crystals form and their size also increases. In addition to the tetrapods, rod-shaped ZnO crystals are observed. The atomic ratio of Zn and O in the ZnO crystals is approximately 1:1 with an increasing process temperature from $1,000^{\circ}C$ to $1,200^{\circ}C$. For the ZnO crystals synthesized at $1,000^{\circ}C$, no luminescence spectrum is observed. A weak visible luminescence is detected for the ZnO crystals prepared at $1,100^{\circ}C$. Ultraviolet and visible luminescence peaks with strong intensities are observed in the luminescence spectrum of the ZnO crystals formed at $1,200^{\circ}C$.