• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.38-39
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• 2003

전기적 저항이 낮은 투명 박막 물질은 현재 flat panel display, electroluminescent device, thin film transistor, solar cell 등 여러 분야에서 연구되고 있다. 그 중에서도 특히 ZnO：Ga는 현재 많이 쓰이는 ITO보다 화학적, 열적으로 안정한 상태를 보이는 투명 전도 산화막 물질로써 본 연구에서는 분광타원법을 이용하여 ZnO：Ga의 광학적 특성을 분석하였다. 본 연구를 위한 시료는 온도에 따른 ZnO：Ga／Sapphire 박막, $O_2$의 압력에 따른 ZnO：Ga／Sapphire 박막, Ga의 doping 농도에 따른 ZnO：Ga／Sapphire 박막으로 제작하였으며, 위상변조형 분광타원계(spectroscopic Phase Modulated Ellipsometer, Jobin-Yvon, UVISEL)를 사용하여 측정대역을 0.74 ~ 4.5 eV, 입사각을 70$^{\circ}$로 하여 측정하였다. (중략)

• Journal of Environmental Science International
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• v.8 no.2
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• pp.241-248
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• 1999

The photocatalytic decolorization and photodegradation of wastewater contamininated with dyes such as methyleneblue tetrahydrate(MBT), methyl orange(MO), phenol red(PR) and the mixed dyes have been studied using a batch reactor in the presence of aerotropic and titania. Degussa P25 titanium oxide was used as the photocatalyst and proved to be effective for the dyes-degradation when irradiated with UV-light source emitting the wavelength of 253.7 nm in the presence of air. In addition to removing the color from the wastewater, the photocatalytic reaction simultaneously reduced the COD and optical density which suggests that the dissolved organic compounds have been photooxidized. The reaction rate of disappearance of the dyes were measured as a function of the irradiation times. The photooxidative procedure of the aquatic solution have the first order reaction-kinetics. The rate constants were increased in the order of PR < MBT < $gL^{-1}-TiO_2$ powder were irradiated with the UV -light source.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1531-1533
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• 2007

We made a high-efficiency lamp with same spec. as a normal lamp by improving physical constants of a lamp and then analyzed varied effects. By applying novel physical constants to an EEFL, we acquired decrease of lamp operating power and voltage.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.10
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• pp.902-908
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• 2002

Homogeneously aligned nematic liquid crystal displays (LCDs) driven by in-plane or fringe field were known to exhibit wide viewing angle and appeared to be black in the off state. However, the existence of spacers inside the cell causes the deformation of the liquid crystal molecules. Such a deformation of the liquid crystal causes light-leakage in the dark state, which lowers contrast ratio of the display. We found that the light-leakage due to deformation of the LC director near the spacer mainly depends on the dielectric anisotropy and the ratio of elastic constants of the LC. In this paper, the mechanism on deformation of the LC near spacer is investigated by optical polarizing microscopy.

• Korean Journal of Optics and Photonics
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• v.24 no.2
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• pp.92-98
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• 2013

The expressions for ellipsometric constants of a sample covered with two thick films are derived, where incoherent superposition of multiply reflected lights inside thick films is properly considered in the frame of the rotating analyzer ellipsometry. The derived expressions are successfully applied to the analysis of a silicon wafer with a thin silicon dioxide film on it, which is placed beneath a cover glass and an air gap.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.08a
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• pp.97-100
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• 2002

$CdGaInS_{4}:Er^{3+}$ single crystal crystallized in the rhombohedral. with lattice constants a = 3.899 $\AA$ and c = 36.970 $\AA$ for $CdGaInS_{4}:Er^{3+}$. The optical absorption measured near the fundamental band edge showed that the optical energy band structure of this compound had a direct and indirect band gaps. the direct and indirect energy gaps are found to be 2.665 and 2.479eV for $CdGaInS_{4}:Er^{3+}$ at 10 K. The photoluminescence spectra of $CdGaInS_{4}:Er^{3+}$ measured in the wavelength ranges of 500 nm~900 nm and 1500~1600 nm at 10 K. Eight sharp emission peaks due to $Er^{3+}$ ion are observed in the regions of 549.5~560.0nm. 661.3~676.5nm. 811.1~ 834.1 nm and 1528.2~1556.0 nm in $CdGaInS_{4}:Er^{3+}$ single crystal. These PL peaks were attributed to the radiative transitions between the split electron energy levels of the $Er^{3+}$ ions occupied at $C_{2v}$ symmetry of the $CdGaInS_4$ single crystals host lattice.

• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.359-364
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• 2014

We report parameters that allow the dielectric functions ${\varepsilon}={\varepsilon}_1+i{\varepsilon}_2$ of $AlAs_xSb_{1-x}$ alloys to be calculated analytically over the entire composition range $0{\leq}x{\leq}1$ in the spectral energy range from 0.74 to 6.0 eV by using the dielectric function parametric model (DFPM). The ${\varepsilon}$ spectra were obtained previously by spectroscopic ellipsometry for x = 0, 0.119, 0.288, 0.681, 0.829, and 1. The ${\varepsilon}$ data are successfully reconstructed and parameterized by six polynomials in excellent agreement with the data. We can determine ${\varepsilon}$ as a continuous function of As composition and energy over the ranges given above, and ${\varepsilon}$ can be converted to complex refractive indices using a simple relationship. We expect these results to be useful for the design of optoelectronic devices and also for in situ monitoring of AlAsSb film growth.

• Journal of the Korean Vacuum Society
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• v.18 no.2
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• pp.133-140
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• 2009

$Ta_{2}O_{5}$ thin films were deposited by RF magnetron sputtering method under various RF power, substrates and oxygen partial pressure. Elliptic constants were measured by using a phase modulated spectroscopic ellipsometer and analyzed with the Tauc-Lorentz dispersion formula and best fit method in the range of 310$\sim$1239 nm. Also, transmittance spectra of the films were measured by UV -Vis spectrophotometer in the range of 300$\sim$1000 nm. From these data, thickness of $Ta_{2}O_{5}$ and surface layer were analyzed and changes of magnitude and shape of dispersion of optical constants according to fabricated conditions were measured. Also, to evaluate thickness and optical constants data analyzed by Tauc-Lorentz dispersion formula, the measured and analyzed transmittance spectra were compared. In result of the comparison, two spectra were in good agreement each other. Accordingly, it indicates that our ellipsometric analysis is valid.

• Korean Journal of Optics and Photonics
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• v.18 no.5
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• pp.351-361
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• 2007

The samples composed of a GST thin film and the protective layers of $ZnS-SiO_2$ or $Al_2O_3$ coated on c-Si substrate were prepared by using the magnetron sputtering method. Samples of three different structures were prepared, that is, i) the GST single film on c-Si substrate, ii) the GST film sandwiched by the protective $ZnS-SiO_2$ layers on c-Si substrate, and iii) the GST film sandwiched by $Al_2O_3$ protective layers on c-Si substrate. The ellipsometric constants in the temperature range from room temperature to $700^{\circ}C$ were obtained by using the in-situ ellipsometer equipped with a conventional heating chamber. The measured ellipsometric constants show strong variations versus temperature. The variation of ellipsometric constants at the temperature region higher than $300^{\circ}C$ shows different behaviors as the ambient medium is changed from in air to in vacuum or the protective layers are changed from $ZnS-SiO_2$ to $Al_2O_3$. Since the long heating time of 1-2 hours is believed to be the origin of the high temperature variation of ellipsometric constants upon the heating environment and the protective layers, a PRAM (Phase-Change Random Access Memory) recorder is introduced to reduce the heating time drastically. By using the PRAM recorder, the GST samples are heated up to $700^{\circ}C$ decomposed preventing its partial evaporation or chemical reactions with adjacent protective layers. The surface image obtained by SEM and the surface micro-roughness verified by AFM also confirmed that samples prepared by the PRAM recorder have smoother surface than the samples prepared by using the conventional heater.

• Journal of the Korean Vacuum Society
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• v.6 no.S1
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• pp.70-74
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• 1997

The study of the thickness dependence of the electron energy structure of Fe, Ni, Ti and Zr sublayers in Ni/Ti and Fe/Zr multilayers by using the experimental and computer simulated optical spectroscopy has been performed. A series of Ni/Ti and Fe/Ze multiayered films (MLF) with a bilayer period of 0.5 - 30 nm and constant (Ni/Ti) / different (Fe/Zr) sublayer thickness ratios were prepared by using computer-controlled double-pair target face-to-face sputtering onto a glass substrate at room temperature (RT) Computer simulation of the resulting optical properties of these MLF was carried out by solving of multireflection problem with a matrix method assuming either "sharp" interfaces resulting in rectangular depth profiles of the components or "mixed" (alloy-like) interfaces of variable thickness between pure-metal sublayers. Optical constants of pure bulk metals as well as equiatomic alloy interfaces were employed in these simulations. It was shown that the difference between experimental and simulated optical properties of the investigated MLF increases with decrease in sublayer thickness. This result allows to conclude that the electronic structures of sublayers below 4-5 nm thickness in mlf differ from the corresponding bulk metals.ponding bulk metals.