• Journal of the Korean Ceramic Society
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• v.45 no.2
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• pp.126-131
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• 2008

In this study, we prepared zirconia gel by the sol-gel method and investigated its photoluminescence properties by varying pyrolysis temperature. The addition of acetic acid into a Zr-alkoxide solution resulted in forming the bidentate ligands with Zr ions and producing a stable gel. At the pyrolysis temperature of $350^{\circ}C$, the zirconia nanocrystals with tetragonal structure gradually appeared in the gel. The PL intensity of the zirconia gel increased with increasing the pyrolysis temperature up to $350^{\circ}C$, but decreased above the temperature. Concurrently, its PL peak wavelength continuously shifted from ${\sim}440\;nm$ to ${\sim}550\;nm$ with the temperature. The PL characteristics of the zirconia gels were closely associated with decomposition of residual organic groups, the formation of the zirconia nanocrystals, and the tetragonal to monoclinic phase transformation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.2
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• pp.133-138
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• 2001

We studied the optical properties of poly(3-hexylthiophene) for applying to the emitting material of organic electro luminescent device. The infrared spectrum and NMR of synthesized polymer gave good evidence for the conjugation of 3-hexylthiophene monomer unit. We confirmed that poly(3-hexylthiophene) contains the HT(head-to-tail)-HT(head-to-Tail) linkage larger than 65% based on NMR analysis. FTIR and raman spectroscopy show that poly(3-hexylthiophene) has two main vibration levels which have an energy about 0.18eV and 0.36eV. Electronic absorption spectra shifted to the shorter wavelength with increasing temperature, which is related to a conformational transition of the polymer. Photoluminescence spectrum generated at low temperature(10K) is separated at 669nm, 733nm and 812nm that it's because of phonon energy generated from the lattice vibration.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.38-41
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• 2002

The variation of photoluminescence(PL) properties of Si thin films was investigated by changing deposition temperatures, Si-rich silicon oxide films on p-type (100) Si substrate have been fabricated by pulsed laser deposition(PLD) technique using a Nd:YAG laser. During deposition, the substrates were kept at the temperature range of room temperature(RT) to $400^{\circ}C$. After deposition, samples were annealed at $800^{\circ}C$ in nitrogen ambient, Strong Blue PL has been observed on RT-deposited Si nanocrystallites. When the deposition temperature was increased over $100^{\circ}C$, PL intensities abruptly decreased. The experimental results show the growing mechanism of Si nanocrystallites by PLD.

• Applied Science and Convergence Technology
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• v.24 no.6
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• pp.245-249
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• 2015

Vertically coupled low density InGaAs quantum dots (QDs) buried in GaAs matrix were grown with migration enhanced molecular beam epitaxy method as a candidate for quantum information processing devices. We performed excitation power-dependent photoluminescence measurements at cryogenic temperature to analyze the effects of vertical coupling according to the variation in thickness of spacer layer. The more intense coupling effects were observed with the thinner spacer layer, which modified emission properties of QDs significantly. The low surface density of QDs was observed by atomic force microscopy, and scanning transmission electron microscopy verified the successful vertical coupling between low density QDs.

• Korean Journal of Materials Research
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• v.16 no.7
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• pp.401-407
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• 2006

ZnO is well-known as a promising material for optical communication systems and electronic displays. ZnO:Er thin films were deposited on c-plane sapphire substrates by rf magnetron sputtering, and the effects of sputtering parameters and the annealing conditions on the luminescence in the visible range were investigated. Luminescent properties depended on the crystallinity of films and annealing atmosphere. Highly c-axis oriented ZnO:Er films showed a strong emission band at 465 nm and a weak emission at 525 nm due to the energy transition of $^{4}I_{15/2}-^{4}F_{5/2}\;and\;^{4}I_{15/2}-^{2}H_{11/2}$, respectively. ZnO:Er thin films annealed at air atmosphere were superior to those annealed in $H_2$ in photoluminescence intensity.

• Korean Journal of Materials Research
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• v.16 no.7
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• pp.445-448
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• 2006

Highly c-axis oriented ZnO thin films were grown on Si(100)substrates with Zn buffer layers. Effects of the Zn buffer layer thickness on the structural and optical qualities of ZnO thin films were investigated using X-ray diffraction (XRD), photoluminescence (PL) and Atomic force microscopy (AFM) analysis techniques. It was confirmed that the quality of a ZnO thin film deposited by rf magnetron sputtering was substantially improved by using a Zn buffer layer. The highest ZnO film quality was obtained with a Zn buffer layer 110 nm thick. The surface roughness of the ZnO thin film increases as the Zn buffer layer thickness increases.

• Applied Science and Convergence Technology
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• v.23 no.5
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• pp.301-307
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• 2014

We have fabricated $SnO_2$/Zn core-shell nanowires by employing a sputtering technique with a Zn target. Scanning electron microscopy indicated that the surface of the nanowires became rougher by the coating. X-ray diffraction of the coated nanowires exhibited the hexagonal Zn diffraction peaks. TEM image of coated structures showed that shell layer was mainly comprised of hexagonal Zn phase. EDX spectra suggested that the shell layer consisted of Zn elements. The photoluminescence spectrum of the coated nanowires in conjunction with Gaussian fitting analysis revealed that the emission was disconvoluted with three Gaussian functions, which are centered at 2.1 eV in the yellow region, 2.4 eV in the green region, and 3.3 eV in the ultraviolet region. We speculated the possible mechanisms of these emission peaks.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.4
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• pp.376-386
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• 2015

MOFs(Metal-Organic Frameworks) are new kinds of materials comprised of metal ions and functional organic ligands, and have large pores in its rigid structures which give the materials various functionalities, including gas absorption, separation, drug delivery etc. Recently photoluminescence properties of MOFs and possibilities of its application to high explosive sensing technologies are drawing attentions from scientists and engineers, because these methods are simple, cheap and easy to perform detection operations. In this article the author reviews the mechanisms of photoluminescence of MOFs, the detection methods of high explosives using MOFs and recent research progresses based on the papers published mainly during last 10 years.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.6
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• pp.236-239
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• 2002

Si nanocrystallites thin films on P-type (100) Si substrate have been fabricated by pulsed laser deposition using a Nd:YAG laser. After deposition, samples were annealed in several environmental gases ;It the temperature range of 400 to $800^{\circ}C$ Hydrogen passivation was then performed in the forming gas (95 % $N_2$ + 5 % $H_2$) for 1 hr. Strong violet-indigo photoluminescence has been observed at room temperature on nitrogen ambient-annealed Si nanocrystallites. We report the variation of photoluminescence (PL) properties of Si thin films by changing annealing temperatures and by using hydrogen passivation. The results could suggest that the origin of violet-indigo PL should be related to the Quantum size effect of Si nanocrystallite.

• Journal of the Korean institute of surface engineering
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• v.45 no.5
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• pp.193-197
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• 2012

The influence of annealing process in an $O_2$ atmosphere on the photoluminescence (PL) spectra properties of ZnS nanowires has been investigated. ZnS nanowires with the diameters approximately 100 nm and the lengths a few tens micrometers were synthesized by evaporating ZnS powders on Si substrates while using an Au thin film as a catalyst. ZnS nanowires had an NBE emission band at 430 nm in the violet region. The emission intensity was improved drastically by a process in which ZnS nanowires were heat-treated at $500^{\circ}C$ in an $O_2$ atmosphere for 45 minutes.