• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.2
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• pp.101-105
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• 2016

The basic characteristics of glass are highly fragile and brittle consequences the ultimate purpose of glass manufacturing is to make a transparent glass with complex shape. In order to solve this problem, mechanical properties of glass can be increased by crystallization of its amorphous glass. However, glass-ceramics has become opaque through crystallization process due to the distracted interface of glass by precipitated particles. This study has been investigated thermal processing conditions of LAS transparent glass-ceramic by using DTA (differential thermal analysis), in order to control size of precipitated particle and then fabricate transparent glass-ceramic. DTA indicated that crystallization peak area was declined with increased nucleation temperature. Subsequently, we have been established optimum temperature for crystallization depending on the nucleation temperature. The transmission and thermal expansion were measured after crystallization, and the size of precipitated particle was identified in range of 20~100 nm by FE-SEM. In addition, by setting the optimized crystallization condition, with high transmission and low thermal expansion glass was synthesized through this experiment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.535-536
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• 2008

Multi-layered thin films of ZnS/$Na_3AlF_6$/ZnS/Cr were deposited on glass substrate by evaporation process. ZnS and $Na_3AlF_6$ were selected as high and low refractive index material, and additionally Cr was chosen as mid reflective layer respectively. The multi-layered thin films were prepared in terms of different optical thickness and different staking sequence and layers. The optical properties were systematically characterized with different optical thickness of $Na_3AlF_6$ especially $0.25\lambda$ and $0.5\lambda$. In order to expect the experimental result, the simulation program, the Essential Macleod Program(EMP) was adopted. Based on the results taken by spectrophotometer at viewing angle $45^{\circ}$, the ZnS/$Na_3AlF_6$/ZnS/Cr multi-layered thin film shows purple colour range in $0.25\lambda$， bluish green in $0.5\lambda$, red purple in $0.75\lambda$, and purple in $1.0\lambda$ respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.3
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• pp.168-174
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• 2016

A conductive oxide-based sapphire glass indium tin oxide/metal electrode and the optical coating, through patterning process was studied in excellent optical properties and integrated touch panel has a high strength. Indium tin oxide conductive oxides of the sapphire glass to 0.3 A at DC magnetron sputtering method of 10 min, gas flow Ar 10 Sccm Ar, $O_2$ 1.0 Sccm the formation conditions of the thin film after annealing at $550^{\circ}C$ for 30min was achieved through a 86% transmittance. In addition, the coating 130 nm hollow silica sol-gel was to improve the optical transmittance of the indium tin oxide to 91%. For the measurement by the modeling hollow silica sol by Macleod simulation and calculated the average values of silica part to the presence or absence in analogy to actual. Refractive index value and the actual value of the material on the simulation the transmittance difference is it does not completely match the air region similar to the actual value (transmission) could be confirmed that the measurement is set to a value of between 5 nm and 10 nm.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.1
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• pp.40-47
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• 2014

In this paper, $Al_2O_3$ film deposited by thermal atomic layer deposition (ALD) with diluted $NH_4OH$ instead of $H_2O$ was suggested for passivation layer and anti-reflection (AR) coating of the p-type crystalline Si (c-Si) solar cell application. It was confirmed that the deposition rate and refractive index of $Al_2O_3$ film was proportional to the $NH_4OH$ concentration. $Al_2O_3$ film deposited with 5 % $NH_4OH$ has the greatest negative fixed oxide charge density ($Q_f$), which can be explained by aluminum vacancies ($V_{Al}$) or oxygen interstitials ($O_i$) under O-rich condition. $Al_2O_3$ film deposited with $NH_4OH$ 5 % condition also shows lower interface trap density ($D_{it}$) distribution than those of other conditions. At $NH_4OH$ 5 % condition, moreover, $Al_2O_3$ film shows the highest excess carrier lifetime (${\tau}_{PCD}$) and the lowest surface recombination velocity ($S_{eff}$), which are linked with its passivation properties. The proposed $Al_2O_3$ film deposited with diluted $NH_4OH$ is very promising for passivation layer and AR coating of the p-type c-Si solar cell.

• Korean Journal of Optics and Photonics
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• v.18 no.3
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• pp.216-220
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• 2007

A widely tunable add/drop filter composed of double ring resonators is implemented with high-index-contrast polymer waveguide. To enhance the productivity, directional couplers are designed to have good fabrication tolerance. The refractive indices of the core and cladding in the 1550 nm wavelength are 1.51 and 1.378, respectively. Drop response in comparison with neighborhood peak gets enhanced by more than 2.9 dB at the wavelength where both rings resonate. This filter can be used to build widely tunable laser diode through hybrid-integration with reflective SOA.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.6
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• pp.357-361
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• 2018

We demonstrated a crack-free ${\alpha}-Ga_2O_3$ on sapphire substrate by horizontal halide vapor phase epitaxy (HVPE). Oxygen-and gallium chloride-synthesized Ga metal and HCl were used as the precursors, and $N_2$ was used as the carrier gas. The HCl flow and growth temperature were controlled in the ranges of 10~30 sccm and $450{\sim}490^{\circ}C$, respectively. The surface of ${\alpha}-Ga_2O_3$ template grown at $470^{\circ}C$ was flat and the root-mean-square (RMS) roughness was ~2 nm. The full width at half maximum (FWHM) values for the symmetric-plane diffractions, were as small as 50 arcsec and those for the asymmetric-plane diffractions were as high as 1,800 arcsec. The crystal quality of ${\alpha}-Ga_2O_3$ on sapphire can be controlled by varying the HCl flow rate and growth temperature.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.3
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• pp.247-253
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• 2011

Purpose: The changes in properties of plastic lens due to heating was investigated. Methods: Plastic lenses of -2.00 diopter were heated at 60-100$^{\circ}C$, and then changes of refractive power, surface condition and transmittance were examined. Results: It was shown that the changes of lens surface due to heating happened at 70$^{\circ}C$ for 1h, 75$^{\circ}C$ for 10 min and 100$^{\circ}C$ 10 sec, respectively. More serious crack was occurred in high index lens and at higher heating temperature, respectively, and transmittance decreased depending on the extent of the damage on the surface of lens. Conclusions: Heating at temperatures above 70$^{\circ}C$ drives cracks on the surface of lens. Optician should recommend an appropriate lens considering the wearer's working conditions and guide for paying attention when they use eyeglasses.

• Korean Journal of Optics and Photonics
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• v.28 no.3
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• pp.97-102
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• 2017

In this paper, we investigate the optical properties of $Ag@Fe_3O_4$ nanoparticles (NPs) composed of a plasmonic core and a magnetic shell. As the $Fe_3O_4$ shell with high refractive index (~2.42) is formed on the surface of the silver NPs having diameter of 60 nm, the wavelength of the localized surface-plasmon resonance (LSPR) is shifted from 420 nm to 650 nm, a so-called "redshift". Furthermore, through the use of three simulation models ($Ag@Fe_3O_4$ NP, $Fe_3O_4$ shell NP, and silver NP), the peak at 410 nm is seen to be the result of scattering by the $Fe_3O_4$ shell with 60 nm thickness, which would be useful in comprehending the complex optics in various nanoscale assemblies using similar NPs.

• Nano
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• v.13 no.10
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• pp.1850124.1-1850124.12
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• 2018

$TiO_2$ films were deposited from oxygen/titanium tetraisopropoxide (TTIP) plasmas at low temperature by Helicon-PECVD at floating potential ($V_f$) or substrate self-bias of -50 V. The influence of titanium precursor partial pressure on the morphology, nanostructure and optical properties was investigated. Low titanium partial pressure ([TTIP] < 0.013 Pa) was applied by controlling the TTIP flow rate which is introduced by its own vapor pressure, whereas higher titanium partial pressure was formed through increasing the flow rate by using a carrier gas (CG). Then the precursor partial pressures [TTIP+CG] = 0:027 Pa and 0.093 Pa were obtained. At $V_f$, all the films exhibit a columnar structure, but the degree of inhomogeneity is decreased with the precursor partial pressure. Phase transformation from anatase ([TTIP] < 0.013 Pa) to amorphous ([TTIP+CG] = 0:093 Pa) has been evidenced since the $O^+_2$ ion to neutral flux ratio in the plasma was decreased and more carbon contained in the film. However, in the case of -50 V, the related growth rate for different precursor partial pressures is slightly (~15%) decreased. The columnar morphology at [TTIP] < 0.013 Pa has been changed into a granular structure, but still homogeneous columns are observed for [TTIP+CG] = 0:027 Pa and 0.093 Pa. Rutile phase has been generated at [TTIP] < 0:013 Pa. Ellipsometry measurements were performed on the films deposited at -50 V; results show that the precursor addition from low to high levels leads to a decrease in refractive index.

• The Journal of the Acoustical Society of Korea
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• v.40 no.1
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• pp.31-37
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• 2021

In this paper, we design an acoustic meta-material silencer that operates at low frequency to reduce noise in duct. A high refractive index meta-material silencer is demonstrated with a combination of zigzag structured thin waveguide and helmholtz resonator, which reduces the speed of sound. Finite Element Method (FEM) analysis via thermo-viscous acoustic mesh is performed in order to calculate thermo-viscous dissipation in sub-wavelength waveguide. Sound power reflection, transmission and absorption coefficients are obtained utilizing 4-Microphone Method. The results show that cut-off frequency and transmission loss can be controlled through adjusting intervals of the zigzag structures. A wide-band acoustic silencer is also suggested by connecting meta-materials in series or parallel.