• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.5
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• pp.435-440
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• 2002

In this study, we have investigated photo-induced changes of optical energy gap( $E_{OP)}$ and photoluminescence (PL) in amorphous ($\alpha$-) S $e_{100-x}$G $e_{x}$ (x=5, 25 and 33) thin films prepared by conventional thermal evaporation method. In the $\alpha$-S $e_{100-x}$G $e_{x}$ thin film, the $E_{OP}$ is obtained by a linear extrapolation of the ($\alpha$hν)$^{\frac{1}{2}}$ versus hν plot to the energy axis using the optical absorption coefficient ($\alpha$) calculated from the extinction coefficient k measured in the wavelength range of 290~900nm. Although the values of $\Delta$ $E_{OP}$ are very different, all films exhibit photo-induced photo-darkening (PD) effect that is a red shift of $E_{OP}$ . In particular, $\Delta$ $E_{OP}$ in $\alpha$-S $e_{75}$ G $e_{25}$ thin film exhibits the largest value (i, e., $\Delta$ $E^{OP}$ ~40meV for $\alpha$-S $e_{95}$ G $e_{5}$ , $\Delta$ $E_{OP}$ ~200meV for $\alpha$-S $e_{75}$ G $e_{25}$ , $\Delta$ $E_{OP}$ ~130meV for $\alpha$-S $e_{67}$ G $e_{33}$ ). PL spectra in $\alpha$-SeGe by hν$_{HeCd}$ have no-Stokes shift (SS) and show a tendency dependent on both composition and illumination time. We explain the energy-induced phenomena such as the PD and thermal bleaching, the native charged-defect generation and the no-SS PL, etc..the PD and thermal bleaching, the native charged-defect generation and the no-SS PL, etc..tc..

• Journal of the Korean Ceramic Society
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• v.34 no.5
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• pp.467-472
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• 1997

Porous silicon was prepared by an anodic etching. The pore size was about 10 nm at an etching time of 20 sec and a current density of 20 mA/$\textrm{cm}^2$. The porous layer was composed of an micro-porous layer (0.6 ${\mu}{\textrm}{m}$) and a macro-porous layer (10 ${\mu}{\textrm}{m}$). Room temperature PL with maximum peak 6700$\AA$ appeared. The peak disappeared by an oxidation reaction when the porous silicon was heated to 100~20$0^{\circ}C$ in atmosphere. In order to avoid the oxidation a heat treatment was done in H2 atmosphere. The micro-pore and Si column, which formed quantum well, were collapsed by the high temperature. The PL maximum peak of heated sample was gradually red-shifted and showed about 300$\AA$ red-shift at 50$0^{\circ}C$. The intensity of PL was maintained to high temperatures in lower pressures. The porous Si was carbonized in C2H2+H2 gas in order to increase thermal stability. The carbonization of the porous Si prevented red-shift of the maximum PL peak caused by sintering effect at high temperatures, and the carbonized porous Si showed Pl signal at higher temperatures by above 20$0^{\circ}C$ than the sample in H2 atmosphere.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.525-528
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• 2004

The photoluminescence (PL) emission of Si nanocrystals synthesized by 400 keV Si ion implanted in $SiO_2$ is studied as a function of ion dose and annealing time. The formation of nanocrystals at around 600 nm from the surface was confirmed by RBS and HRTEM, and the Si nanocrystals showed a wide and very intense PL emission at 700-900 nm. The intensity of this emission showed a typical behaviour with a fast transitory increase to reach a saturation with the annealing time, however, the red shift increased continuously because of the Ostwald ripening. The oversaturation of dose derived a decrease of PL intensity because of the diminishment of quantum confinement. A strong enhancement of PL intensity by H passivation was confirmed also, and the possible mechanism is discussed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.1
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• pp.31-35
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• 2003

The PL data bases reveal the fact that a part of lattice of HPHT treated diamond is reconfigured by the reduction, elimination, generation, and movement of vacancies and interstitials as well as of impurity elements. In particular, this very sensitive method clearly illustrated that minute amount of nitrogen impurities is present in all of these type IIa diamonds, and reveal the presence of a considerable number of point defects dispersed throughout the crystal lattice.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.195-197
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• 2002

CdTe quantum dots(QDs) were synthesized in aqueous solution by colloidal method. Photoluminescence(PL) spectra of the synthesized CdTe QDs revealed the intensity of PL peaks was stronger as the condensation time was longer. This result was thought because annealing effect by thermal energy transferred during condensation eliminated defects which act as traps and recombination centers in CdTe particle. PL intensity has stron dependence of Te precursor concentration. It confirmed the ratio of Te ion to Cd ion added during synthesis affected the particle size and size distribution of the CdTe QDs. Finally, the synthesized CdTe QDs were identified to be cubic structured CdTe quantum dots by X-ray diffraction(XRD).

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.9-10
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• 2008

Triple layers structure of $SiO_2$/ZnS:Mn/ZnS was synthesized by using ion substitution and chemical precipitation method. Each layer thickness was controlled by adjusting the concentration of manganese (II) acetate ($Mn(CH_3COO)_2$) and tetraethyl orthosilicate (TEOS). The structure and morphology of prepared phosphors were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microscopic analyzer (EPMA). Photoluminescence (PL) properties of ZnS with different layer thickness and amount of Mn activator were analyzed by PL spectrometer. PL emission intensity and PL stability were analyzed for evaluating effects of Mn activator.

• Journal of the Korean Vacuum Society
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• v.17 no.2
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• pp.170-174
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• 2008

We have studied, using Raman and photoluminescence (PL) spectroscopy, material property changes of single-walled carbon nanotubes (SWCNTs) dispersed in sodium dodecyl sulfate(SDS) aqueous solution by ultrasonication. Radial breathing mode Raman intensities of the dispersed SWCNTs shows different behavior depending on their chiralities as the sonication time increases. As the amount of SWCNTs dispersed in 1wt% SDS solution increases, both a downshift of the G-band Raman frequency and an enhancement in the PL intensity were observed.

• Journal of the Mineralogical Society of Korea
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• v.22 no.2
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• pp.81-86
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• 2009

The luminescence and fluorescence were investigated by photoluminescence spectroscopy for six gemstones which exhibit color change effect. The shape of luminescence peaks appears different when observed by a photoluminescence spectroscopewith a 514 nm Ar laser source. However, it was not possible to observe the difference in the spectra between the natural and synthetic origins for the same type of gemstones. It was found that the photoluminescence spectrum was related to the crystal structure of the stones. Photoluminescence spectra using a 325 nm He-Cd source reveal that fluorescence is relatively strong for synthetic alexandrite, synthetic color change sapphire and natural alexandrite comparing to the rest of gemstones examined.

• Korean Journal of Materials Research
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• v.28 no.2
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• pp.124-128
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• 2018

N-type porous silicon (PS) layers and thermally oxidized PS layers have been characterized by various measuring techniques such as photoluminescence (PL), Raman spectroscopy, IR, HRSEM and transmittance measurements. The top surface of PS layer shows a stronger photoluminescence peak than its bottom part, and this is ascribed to the difference in number of fine silicon particles of 2~3 nm in diameter. Observed characteristics of PL spectra are explained in terms of microstructures in the n-type PS layers. Common features for both p-type and n-type PS layers are as follows: the parts which can emit visible photoluminescence are not amorphous, but crystalline, and such parts are composed of nanocrystallites of several nm's whose orientations are slightly different from Si substrate, and such fine silicon particles absorb much hydrogen atoms near the surfaces. Light emission is strongly dependent on such fine silicon particles. Photoluminescence is due to charge carrier confinement in such three dimensional structure (sponge-like structure). Characteristics of visible light emission from n-type PS can be explained in terms of modification of band structure accompanied by bandgap widening and localized levels in bandstructure. It is also shown that hydrogen and oxygen atoms existing on residual silicon parts play an important role on emission stability.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.362-365
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• 2015

Silica encapsulated ZnSe quantum dots (QDs) were prepared by employing two microemulsion systems: AOT/water/cyclohexane microemulsions containing ZnSe quantum dots with NP5/water/cyclohexane microemulsions containing tetraethylorthosilicate (TEOS). Using this method, cubic zinc blende nanoparticles (3 nm in diameter) were synthesized and encapsulated by silica nanoparticles (20 nm in diameter). The temperature dependence of photoluminescence (PL) for silica-encapsulated ZnSe QDs was investigated to evaluate this material as a temperature sensor media. The fluorescence emission intensity of silica-encapsulated ZnSe nanoparticles (NPs) was decreased with an increase of ambient temperature over the range from $30^{\circ}C$ to $60^{\circ}C$ and a linear relationship between the temperature and the emission intensity was observed. In addition, the temperature dependence of PL intensity for silica-encapsulated ZnSe NPs showed a reversible pattern on ambient temperature. A reversible temperature dependence of the luminescence combined with its insensitivity toward quenching by oxygen due to silica coating established this material as an attractive media for temperature sensor applications.