• Journal of the Semiconductor & Display Technology
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• v.21 no.3
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• pp.39-44
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• 2022

The light extraction technology for improving the light efficiency of OLEDs is the core technology for extracting the light inside the OLEDs to the outside. This study demonstrates a simple method to generate random nanostructures (RNSs) containing high refractive index nanoparticles to improve light extraction and viewing angle characteristics. A simple dry low-temperature process makes the nanostructured scattering layer on the polymer resin widely used in the industry. The scattering layer has the shape of randomly distributed nanorods. To control optical properties, we focused on changing the shape and density of RNSs and adjusting the concentration of high refractive index nanoparticles. As a result, the film of the present invention exhibits a perpendicular transmittance of 85% at a wavelength of 550 nm. This film was used as a scattering layer to reduce substrate mode loss and improve EL efficiency in OLEDs.

• Structural Engineering and Mechanics
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• v.84 no.6
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• pp.813-822
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• 2022

In this article, the buckling and free vibration of multi-directional FGM sandwich plates are investigated. The material properties of FGM sandwich plates are assumed to be varying continuously in the in the longitudinal, transverse and thickness directions. The material properties are evaluated based on Voigt's micro-mechanical model considering power law distribution method with arbitrary power index. Equations of motion for the buckling and vibration analysis of multi-directional FGM sandwich plate are obtained based on refined shear deformation theory. Analytical solution for simply supported multidirectional FGM sandwich plate is carried out using Navier's solution technique. The FGM sandwich plate considered in this work has a homogeneous ceramic core and two functionally graded face sheets. Influence of volume fraction index in the longitudinal, transverse and thickness direction, layer thickness, and geometrical parameter over natural frequency and critical buckling load of multi-directional FGM sandwich plate is investigated. The finding shows a multi-directional functionally graded structures perform better compared to uni-directional gradation. Hence, critical grading parameters have been identified which will guide researchers in selecting fabrication routes for improving the performance of such structures.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.6
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• pp.597-600
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• 1999

By periodically varying the current density and etching time during anodic oxidation of crustalline silicon wafers in 15% HF-ethanol solution, we obtained porous silicon multilayers which have periodically varying refractive index. We fabricated the porous silicon microcavity (PSM) which consist of porous silicon multilayers (I), active layer of porous silicon, and porous silicon multilayers (II) and investigated its physical properties. The AFM (Atomic Force Microscope) measurement from the cross section of multilayers (I and II) shows uniformity of high refractive index and low index layers as well as the active layer. We observed the characteristics of Bragg reflector when the thickness of layers was 1/4 and the thickness of active layer was twice of the effective wavelength, which can be used as a filter for specific wavelength. We found the emission characteristic from the PSM, which FWHM (full width half maximum) was considerably decreased and emission intensity was increased.

• Journal of environmental and Sanitary engineering
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• v.18 no.4
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• pp.52-63
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• 2003

This paper investigated Taxi drivers physical subjective symptoms and what factors were interviewed caused the symptoms. The 600 owning taxi-drivers in Seoul during four months from August 1st, 2003 to November 30th, 2003. 1. The average age of the owning taxi-drivers was generally quite high 54 years old. It was very high index compared with the Todai Health Index(THI) and Cornell Medical Index(CMI) of health check tables. 2. According to the age in THI health check table, the complains of mental subjective symptom by reason of age was high among 31 to 40 years old. People who belonged that age group showed high fabrication(L), digestion(C) and aggressiveness(F). The results showed the complains of mental subjective symptom. All items except tiredness(I), melancholia(N), and hypersensitivity(P) were commonly reported by people in their sixties. On the other hand, melancholia(N) and hypersensitivity(P), people in their forties were investigated highly. Statistically, the items of heartㆍblood stream(C) and digestion(D) systems were similar between the two ages, but anger(Q) was different. (p<0.05) 3. From the complains of mental and physical subjective symptoms about work satisfaction on the THI health check table, all items except eyeㆍskin trouble(B) showed strong dissatisfaction. From the complains of mental and physical subjective symptoms about work satisfaction on the CMI health check table, the items of respiratory system(B), digestion(D), nervous system(G), miscellaneous(K), inadequancy(M), and anger(Q) showed similar results. Otherwise, heartㆍblood stream(C) showed statistically different. 4. From the complains of mental and physical subjective symptoms on salary satisfaction in the THI health check table, in the case of people receiving around 1 million won, the complains of physical symptoms showed high among all items except for the respiratory(A) and digestion(C) systems. The eyeㆍskin trouble(B) item showed statistical similarity. The complains of mental and physical subjective symptoms according to a salary degree on the CMI health check table was completely different from the above results. In people received around 1~1.5million won, all items except anxiety(O) showed high. The hypersensitivity(P) item showed statistically different.

• Korean Journal of Materials Research
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• v.24 no.12
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• pp.689-693
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• 2014

Anti-reflection coating films have used to increase the transmittance of displays and enhance the efficiency of solar cells. Hydrophobic anti-reflection coating films were fabricated on a glass substrate by sol-gel method. To fabricate an anti-reflection film with a high transmittance, poly ethylene glycol (PEG) was added to tetraethyl orthosilicate (TEOS) solution. The content of PEG was changed from 1 to 4 wt% in order to control the morphology, thickness, and refractive index of the $SiO_2$ thin films. The reflectance and transmittance of both sides of the coated thin film fabricated with PEG 4 wt% solution were 0.3% and 99.4% at 500 nm wavelength. The refractive index and thickness of the thin film were n = 1.29 and d = 105 nm. Fluoro alkyl silane (FAS) was used for hydrophobic treatment on the surface of the anti-reflection thin film. The contact angle was increased from $13.2^{\circ}$ to $113.7^{\circ}$ after hydrophobic treatment.

• Journal of the Korean Ceramic Society
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• v.35 no.4
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• pp.364-370
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• 1998

Boron-phoshor-silicate glass was fabricated on Si substrates by FHD(Flame Hydrolysis Deposition) The microstructrue of silica soot deposited at various conditon such as composition and substrate temperature was analysed by SEM. After consolidation the refractive index and composition of the silica layer were in-vestigated. For refractive index control B, P and Ge were used as additive elements while B and Ge oxides are easily mixed into $SiO_2$, P oxide($B_2O_3$) doping is difficult because of the volatile property due to low melt-ing point. Boron-phosphorous-silicate glass (BPSG) layer were fabricated using bertical torch and optimized flame temperature substrate temperature and distance of torch and substrate. P concentration of BPSG lay-er measured 3.3 Wt% and the consolidation temperature was lower than $1180^{\circ}C$. The measured refractive index of BPSG silica layer in $1.55\;\mu\textrm{m}$ wavelength was $1.4480{\pm}1{\times}10^{-1}$ and the thickness was $22{\pm}1\;\mu\textrm{m}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1367-1374
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• 2008

A new high-gain Fabry-$P{\acute{e}}rot$ cavity antenna for wireless broadband internet(Wibro) base station antennas, which is covered with metamaterial superstrate presenting simultaneous negative values of permittivity and permeability, is proposed. To facilitate the fabrication process using the printed circuit board(PCB) technology of today, a new planar-type metamaterial superstrate is designed, which shows negative and low positive values of a refractive index near the Wibro service frequency band. And the principle of antenna gain enhancement is analyzed from the two different view points of effectively low refractive index and of the Fabry-$P{\acute{e}}rot$ resonance condition. Single square patch antenna is used as a feeder. The separation distance is determined by considering the reflection phases of the metamaterial superstrate and the substrate satisfying Fabry-$P{\acute{e}}rot$ resonance condition, respectively. Comparison between the prediction and the measurement shows good agreement, which verifies the validity of our design approach.

• Journal of the Korean Vacuum Society
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• v.19 no.2
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• pp.148-154
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• 2010

We have fabricated $SiO_2$ oxidation thin films by TCP-CVD (transformer coupled plasma chemical vapor deposition) method for passivation layer of OLED (organic light emitting diode). The purpose of this paper is to control and estimate the deposition rate and refracive index characteristics with process parameters. They are power, gas condition, distance of source and substrate and process temperature. The results show that transmittance of thin films is over 90%, rapid deposition rate and stable reflective index from 1.4 to 1.5 at controled process conditions. They are $SiH_4$ : $O_2$ = 30 : 60 [sccm] gas condition, 70 [mm] distance of source and substrate, no-biased substrate and under 80 [$^{\circ}C$] process temperature.

• Transactions on Electrical and Electronic Materials
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• v.1 no.4
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• pp.11-15
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• 2000

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 MgFe$_2$/GeO$_2$. We investigated GeO$_2$ 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 GeO$_2$ film showed deposition temperature strong dependence. The GeO$_2$ at 400$\^{C}$ exhibited a strong (111) preferred orientation and the lowest surface roughness of 6.87 $\AA$. Refractive index of MgFe$_2$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 ㎛ to 1.1 ㎛. Solar cells with a structure of MgFe$_2$/GeO$_2$/Ag/N$\^$+//p-type Si/P$\^$+//Al were investigated with the without DLAR coatings. We achieved the efficiency of solar cells greater than 15% with 3.12% improvement with DLAR coatings. Further details about MgFe$_2$,GeO$_2$ films, and cell fabrication parameters are presented in this paper.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.3
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• pp.39-45
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• 1984

Submicron gratings are fabricated holographically on thin film single mode and multimode waveguides. Thin film waveguides are made by spin-coating polyurethane solution on the substrates of microscope slide glass and Corning 7059 glass. In order to characterize thin film waveguides, the refract사e index and the thickness of thin films are measured by using the m-line spectroscopy. The fabricated gratings are tested as a grating coupler, a mode converter, and a beam splitter. Also chirped gratings are fabricated to observe beam expansion phenomena and thus the possibility of the wavelength demultiplexing.