• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.10
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• pp.447-450
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• 2003

This paper presents a process optimization of antireflection (AR) coating on crystalline Si solar cells. Theoretical and experimental investigations were performed on a double-layer AR (DLAR) coating of MgF$_2$/CeO$_2$. We investigated CeO$_2$ films as an AR layer because they have a proper refractive index of 2.46 and demonstrate the same lattice constant as Si substrate. RF sputter grown CeO$_2$ film showed strong dependence on a deposition temperature. The CeO$_2$ deposited at 40$0^{\circ}C$ exhibited a strong (111) preferred orientation and the lowest surface roughness of 6.87 $\AA$. Refractive index of MgF$_2$ film was measured as 1.386 for the most of growth temperature. An optimized DLAR coating showed a reflectance as low as 2.04% in the wavelengths ranged from 0.4${\mu}{\textrm}{m}$ to 1.1${\mu}{\textrm}{m}$. We achieved the efficiencies of solar cells greater than 15% with 3.12% improvement with DLAR coatings. Further details on MgF$_2$, CeO$_2$ films, and cell fabrication parameters are presented in this paper.

• Journal of the Semiconductor & Display Technology
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• v.8 no.1
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• pp.33-38
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• 2009

We have investigated the effect of the ambient gases on the characteristics of AZO thin films for the OLED (organic light emitting diodes) devices. These AZO thin films are deposited by rf-magnetron sputtering under different ambient gases (Ar, Ar+$O_2$, and Ar+$H_2$) at 300. In order to investigate the influences of the oxygen and hydrogen, the flow rate of oxygen and hydrogen in argon mixing gas has been changed from 0.2sccm to 1sccm and from 0.5sccm to 5sccm, respectively. The AZO thin films were preferred oriented to (002) direction regardless of ambient gases. The electrical resistivity of AZO film increased with increasing flow rate of $O_2$ under Ar+$O_2$ while under Ar+$H_2$ atmosphere the electrical resistivity showed minimum value near 1sccm of $H_2$. All the films showed the average transmittance over 80% in the visible range. The OLED device was fabricated with different AZO substrates made by configuration of AZO/$\acute{a}$-NPD/DPVB/$Alq_3$/LiF/Al to elucidate the performance of AZO substrate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.21-24
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• 2000

Ferroelectric YMnO$_3$ thin films are excellent dielectric materials for high integrated ferroelectric random access memory (FRAM) with metal-ferroelectric-silicon field effect transistor (MFSFET) structure. In this study, YMnO$_3$ thin films were etched with C1$_2$/Ar gas chemistries in inductively coupled plasma (ICP). The maximum etch rate of YMnO$_3$ thin films is 285 $\AA$/min under C1$_2$/Ar of 10/0, 600 W/-200 V and 15 mTorr. The selectivities of YMnO$_3$ over CeO$_2$ and $Y_2$O$_3$ are 2.85, 1.72, respectively. The results of x-ray photoelectron spectroscopy (XPS) reflect that Y is removed dominantly by chemical reaction between Y and Cl, while Mn is removed more effective by Ar ion bombardment than chemical reaction. The results of secondary ion mass spectrometer (SIMS) were equal to these of XPS. The etch profile of the etched YMnO$_3$ film is approximately 65$^{\circ}$and free of residues at the sidewall.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.11
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• pp.991-994
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• 2007

In this paper, we have designed the anti-reflection(AR) coating for $1400{\sim}1600$ nm wavelength range on the ferrule facet of optical connector. The low-temperature ion-assisted deposition was applied to AR coating on the ferrule facet in order to avoid damage of optical connector. We have measured the refractive index of coating film($Ta_2O_5\;and\;SiO_2$) using the ellipsometer and optimized the film thickness using the SEM and thickness measurement equipment. UV-VIS-NIR spectrophotometer is used to measure transmissivity of the AR coated ferrule facet. The refractive index of $Ta_2O_5\;and\;SiO_2$ is $2.123{\sim}2.125$ and $1.44{\sim}1.442$, respectively, for $1400{\sim}1600$ nm wavelength range. The transmissivity of the AR coated ferule facet is more than 99.8 % for $1425{\sim}1575$ nm wavelength range and more than 99.5 % for $1400{\sim}1600$ nm wavelength range. The return loss of the AR coated ferrule facet is 30.1 dB.

• Bulletin of the Korean Chemical Society
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• v.15 no.8
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• pp.663-669
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• 1994

Decay kinetics of Ga(5s), Ga(5p) and Ga(4d) atoms in Ar were studied by laser induced fluorescence technique. Theground state gallium atoms in the gas phase were generated by pulsed dc discharge of trimethyl gallium and argon mixtures. Both pulsed discharge and YAG-DYE laser system were controlled by a dual channel pulse generator and the delay time between the end of discharge and laser pulses was set 3.0-6.0 ms. The Ga(5s) and Ga(4d) atoms were generated by single photon excitation from the ground state Ga atoms and radiative lifetimes as well as the total quenching rate constants in Ar were obtained from the pressure dependence of the fluorescence decay rates. The Ga(5p) atoms were populated by a two-photon excitation method and the cascade fluorescence from Ga(5s) atoms were analyzed to extract quenching rate constant of Ga(5p) atoms by Ar in addition to radiative lifetimes of Ga(5p) state. The magnitudes of the quenching rate constants by Ar for the low-lying excited states of Ga atoms are 1.6-3$ {\times}10^{-11}cm^3$ molecul$e^{-1}s^{-1}$, which are much larger than those for alkali, alkaline earth and Group 12 metals. Based on the measured rate constants, kinetic simulations were done to assign state-to-state rate constants.

• Aerospace Engineering and Technology
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• v.13 no.1
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• pp.153-165
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• 2014

Multi-rotor UAVs are utilized in various fields because of the advantages such that a hovering capability such as helicopters, a simple structure and a relatively high thrust. Recently, AR.Drone manufactured by Parrot is easily operated by beginner due to its internal stabilization loop in the on-board computer and it can be easily applied on various researches for the multi-rotor UAVs by providing an SDK(Software Development Kit). Further this platform can be suitably used for application to swarm flight since it is low cost and relatively small. Therefore, in this paper, we introduce the development process of the controller for indoor swarm flight by using the AR.Drone.

• Journal of the Korean Society of Safety
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• v.16 no.1
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• pp.88-93
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• 2001

This study discusses frequency analysis based on autoregressive (AR) time series model, and process characterization in orthogonal cutting of a fiber-matrix composite materials. A sparsely distributed idealized composite material, namely a glass reinforced polyester (GFRP) was used as workpiece. Analysis method employs a force sensor and the signals from the sensor are processed using AR time series model. The resulting pattern vectors of AR coefficients are then passed to the feature extraction block. Inside the feature extraction block, only those features that are most sensitive to different types of cutting mechanisms are selected. The experimental correlations between the different chip formation mechanisms and AR model coefficients are established.

• Clinical and Experimental Reproductive Medicine
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• v.24 no.1
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• pp.27-34
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• 1997

This study aimed to evaluate the effect of seminal vesicle fluid (SVF) on the acrosome reaction (AR) occurred spontaneously or induced by $Ca^{2+}$ ionophore A23187, follicular fluid, and progesterone in mouse epididymal sperm. SVF was divided into high (MW>10 kD) and low (MW<10 kD) fractions by ultrafiltration. The low MW fraction of SVF decreased the rate of spontaneous AR, however the high MW fraction did not. It suggested that the low MW fraction of SVF might have contained decapacitation factor(s) responsible for prolonging of time need for capacitation. When sperm preincubated for 60 min in the presence of SVF, the rate of AR induced by A23187 was decreased, but prolongation of preincubation time for 120 min significantly potentiated the AR by A23187. It suggested that addition of SVF into sperm preincubation medium imposed the epididymal sperm a condition similar to ejaculation. AR induced by human follicular fluid or progesterone was also inhibited by SVF. It suggested that substance in SVF might have affected AR of mouse sperm by inhibiting the interaction between AR inducing ligands and sperm surface receptors involved in acrosomal exocytosis.

• Journal of Welding and Joining
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• v.26 no.6
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• pp.42-47
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• 2008

TIG welding enables to produce high quality weldment. However it has some problems such as shallow penetration and large distortion due to low penetration aspect ratio after welding. In order to overcome those problems, there are many ongoing studies on A-TIG welding, which use active flux. In this study, the effect of arc length and shield gas on penetration aspect ratio with melt-run welding on STS 304 6t, on which active flux was spreaded, was investigated. Arc length was changed from 1mm to 3mm, and aspect ratio became higher as arc length was decreased in this range. 100% Ar gas, Ar-$H_2$ mixed gas, Ar-He mixed gas, and 100% He gas were used as shield gas in this study. When Ar-$H_2$ mixed gas, Ar-He mixed gas, and 100% He gas were applied, penetration and melting efficiency were both increased as compared with 100% Ar gas. Aspect ratio was the highest with Ar-2.5% $H_2$ mixed gas.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1321-1322
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• 2007

$Ar/Cl_2$, $Ar/CH_4$ 및 $Ar/Cl_{2}/CH_{4}$ 유도결합 플라즈마의 가스 혼합비에 따른 BLT 박막의 식각 메커니즘과 선택비, 식각 후 박막 표면의 조성변화를 조사하였다. BLT 박막의 최대식각률은 $Ar/Cl_2$ 플라즈마에서의 Ar 가스 혼합비가 80%일 때 50.8 nm의 값을 보였다. 이 때, 1sccm의 $CH_4$ 첨가를 통하여 선택비와 식각률을 개선할 수 있었다. 박막 표면의 xPS 분석을 통해 BLT 박막 표면의 조성변화는 Cl 원자와의 반응에 의한 화학적 식각 손상이 H 원자와의 반응에 의한 그것보다 크다는 것을 알 수 있었다.