• Journal of the Korean Ceramic Society
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• v.32 no.5
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• pp.617-625
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• 1995

In order to reduce reflectance of soda-lime glass having average reflectance of 7.35% and refractive index of 1.53, single (SiO2), double (SiO2/20SiO2-80ZrO2), and triple (SiO2/ZrO2/75SiO2-25ZrO2) layers were designed and fabricated on the glass substrate by Sol-Gel method. Stble sols of SiO2-ZrO2 binary system for antireflective (AR) coatings were synthesized with tetraethyl orthosilicate (TEOS) and zirconium n-butoxide as precursors and ethylacetoacetate (EAcAc) as a chelating agent in an atmosphere environment. Films were deposited on soda-lime glass at the withdrawal rates of 3~11 cm/min using the prepared polymeric sols by dip-coating and they were heat-treated at 45$0^{\circ}C$ for 10 min to obtain homogeneous, amorphous and crack-free films. In case of SiO2-ZrO2 binary system, refractive index of film increased with an increase of ZrO2 mol%. Designed optical constant of films could be obtained through varying the withdrawal rate. In the visible region (380~780nm), reflectance was measured with UV/VIS/NIR Spectrophotometer. Average reflectances of the prepared single-layer [SiO2 (n=1.46, t=103nm)], double-layer [SiO2 (n=1.46, t=1-4nm)/20SiO2-80ZrO2 (n=1.81, t=82nm)], and triple-layer [SiO2 (n=1.46, t=104nm)/ZrO2 (n=1.90, t=80nm)/75SiO2-25ZrO2 (n=1.61, t=94 nm)] were 4.74%, 0.75% and 0.38%, respectively.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.145-156
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• 1990

In this study, thermophysical properties of the engineering ceramic materials such as $Al_{2}$O$_{3}$, Si$_{3}$N$_{4}$ and SiC were measured b y a single rectangular pulse heating method. The values of thermal diffusivities, specific heats, and thermal conductivities were measured as a function of temperature ranging form room temperature to 1300K. The measured thermal properties of one group of ceramic material were compared with those of other group and discussed in detail in connection with the chemical composition. Thus, some criteria for thermal design with the engineering ceramic materials were proposed.

• Journal of the Korean institute of surface engineering
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• v.35 no.3
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• pp.133-140
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• 2002

The Ti-Si-N coating layers were synthesized on SKD 11 steel substrate by a DC reactive magnetron co-sputtering technique with separate Ti and Si targets. The high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) analyses for the coating layers revealed that microstructure of Ti-Si-N layer was nanocomposite, consisting of nano-sized TiN crystallites surrounded by amorphous $Si_3$$N_4$ phase. The highest hardness value of about 39 GPa was obtained at the Si content of ~11at.%, where the microstructure had fine TiN crystallites (about 5nm in size) dispersed uniformly in amorphous matrix. As the Si content in Ti-Si-N films increased, the TiN crystallites became from aligned to randomly oriented microstructure, finer, and fully penetrated by amorphous phase. Free Si appeared in the layers due to the deficit of nitrogen source at higher Si content. Friction coefficient and wear rate of the Ti-Si-N coating layer significantly decreased with increase of relative humidity. The self-lubricating tribe-layers such as $SiO_2$ or (OH)$Si_2$ seemed to play an important role in the wear behavior of Ti-Si-N film against steel.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.7-8
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• 2008

The memory characteristics of charge trap flash (CTF) with $HfO_2$ charge trap layer were investigated. Especially, we focused on the effects of tunnel barrier engineering consisted of $SiO_2/Si_3N_4/SiO_2$ (ONO) stack or $Si_3N_4/SiO_2/Si_3N_4$ (NON) stack. The programming and erasing characteristics were significantly enhanced by using ONO or NON tunnel barrier. These improvement are due to the increase of tunneling current by using engineered tunnel barrier. As a result, the engineered tunnel barrier is a promising technique for non-volatile flash memory applications.

• Advances in materials Research
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• v.3 no.4
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• pp.227-232
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• 2014

$Ce^{4+}$, $Eu^{3+}$, $Tb^{3+}$ co-doped $Ca_3Si_3O_8F_2$ phosphor was synthesized via solid state reaction method using $CaF_2$, $CaCO_3$ and $SiO_2$ as raw materials for the host and $Eu_2O_3$, $CeO_2$, and $Tb_4O_7$ as activators. The luminescent properties of the phosphor was analysed by spectrofluorophotometer at room temperature. The effect of excitation wavelengths on the luminescent properties of the phosphor i.e. under near-ultraviolet (nUV) and visible excitations was investigated. The emission peaks of $Ce^{4+}$, $Eu^{3+}$, $Tb^{3+}$ co-doped $Ca_3Si_3O_8F_2$ phosphor lays at 480(blue band), 550(green band) and 611nm (red band) under 380nm excitation wavelength, attributed to the $Ce^{4+}$ ion, $Tb^{3+}$ ion and $Eu^{3+}$ ions respectively. The results reveal that the phosphor emits white light upon nUV (380nm) / visible (465nm) illumination, and a red light upon 395nm / 535nm illumination. RE ions doped $Ca_3Si_3O_8F_2$ is a promising white light phosphor for LEDs. The emission colours can be seen using Commission international de l'eclairage (CIE) co-ordinates. A single host phosphor emitting different colours under different excitations indicates that it is a potential phosphor having applications in many fields.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.594-597
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• 1999

The new green and red phosphors for PDP application activated by T $b^{3+}$ and E $u^{3+}$ were synthesized, and their photoluminance properties were investigated. It was found that the brightness of $Al_3$Gd $B_4$ $O_{12}$ :T $b^{3+}$ green phosphor under 147nm VUV irradiation was higher than that of commercial Z $n_2$ $SiO_4$:M $n^{2+}$ phosphor. But the emitting intensity of A1$_3$Gd $B_4$ $O^{12}$ :E $u^{3+}$ red phosphor was inferior to the commercial (Y,Gd)B $O_3$:E $u^{3+}$. $Al_3$Gd $B_4$ $O_{12}$ Phosphor had a strong excitation band at 160nm associated with the host absorption, and also the photoluminance excitation intensity of $Al_3$Gd $B_4$ $O_{12}$ :T $b^{3+}$ was higher than that of Z $n_2$ $SiO_4$:M $n^{2+}$, but the intensity of $Al_3$Gd $B_4$ $O_{12}$ :E $u^{3+}$ phosphor was smaller than (Y,Gd)B $O_3$:E $u^{3+}$ phosphor In the VUV range. C $e^{3+}$ co-doping in A1$_3$Gd $B_4$ $O^{12}$ :E $u^{3+}$ and substitution of $Al^{3+}$ by G $a^{3+}$ A1$_3$Gd $B_4$ $O^{12}$ :E $u^{3+}$ phosphor were tried, but they did not improved the optical property .d the optical property .ty .

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.12
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• pp.1283-1288
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• 2004

Metal-ferroelectric-insulator-semiconductor(WFIS) capacitors using rapid thermal annealed LiNbO$_3$/AlN/Si(100) structure were fabricated and demonstrated nonvolatile memory operations. The capacitors on highly doped Si wafer showed hysteresis behavior like a butterfly shape due to the ferroelectric nature of the LiNbO$_3$ films. The typical dielectric constant value of LiNbO$_3$ film in the MFIS device was about 27, The gate leakage current density of the MFIS capacitor was 10$^{-9}$ A/cm$^2$ order at the electric field of 500 kV/cm. The typical measured remnant polarization(2P$_{r}$) and coercive filed(Ec) values were about 1.2 $\mu$C/cm$^2$ and 120 kV/cm, respectively The ferroelectric capacitors showed no polarization degradation up to 10$^{11}$ switching cycles when subjected to symmetric bipolar voltage pulses of 1 MHz. The switching charges degraded only by 10 % of their initial values after 4 days at room temperature.e.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.447-447
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• 2012

최근 생물전자공학에서 의료 산업 환경 등 많은 분야에 응용 가능한 바이오센서의 연구가 활발해지고 있다. 그 중 의료 분야에서, 수소이온 ($H^+$)의 농도 감지는 인간의 질병을 예측하는데 중요한 지표가 되며 이러한 수소이온 ($H^+$) 농도의 변화를 실시간으로 감지하기 위해 반도체를 기반으로 한 다양한 pH 센서가 제안되었다. Ion sensitive field effect transistor (ISFET), electrolyte-insulator-semiconductor (EIS)는 대표적인 반도체 pH센서로, 작은 소자 크기, 견고한 구조, 빠른 응답속도와 CMOS 공정과의 호환성이 좋다는 장점이 있다. 특히, EIS는 제조공정이 간단하고 감지막의 감지 특성 평가가 용이하기 때문에 지속적으로 연구되고 있는 pH 센서이다. 센서의 감지 특성을 평가함에 있어 감지막의 감지감도와 안정성이 우수해야 하며 이를 위해 high-k 물질이 감지막으로 사용되고 있다. 추가적으로 high-k 물질은 기존의 $SiO_2$와 $Si_3N_4$를 대신하여 높은 유전상수로 인한 고성능, 고감도 센서제작을 가능케 한다. 본 연구에서는, high-k 물질인 $HfO_2$, $Ta_2O_5$, $ZrO_2$, $Al_2O_3$를 각각 $SiO_2$ 완충막에 적층한 이단 감지막을 제작하였고, 그 특성을 기존의 $SiO_2$, $Si_3N_4$ 감지막의 감지특성과 비교하였다. pH 감지 특성을 평가해 본 결과, 기존의 $SiO_2$, $Si_3N_4$ 감지막과 비교했을 때 high-k 물질의 감지막을 갖는 EIS pH 센서에서 감지감도와 안정성 모두 우수하게 나타났다. 특히, high-k 물질 중 $HfO_2$에서 감지감도가 다소 크게 평가되었으나, 화학적 용액에 대한 안정성은 떨어졌다. 반면에 $Al_2O_3$과 $Ta_2O_5$은 화학용액에 대한 안정성 측면에서 최적의 특성을 보임을 확인하였다. 결론적으로, high-k 물질에 대한 전반적인 평가를 통하여 높은 pH 감지감도뿐만 아니라 우수한 안정성의 EIS pH 센서를 제작 할 수 있었다.

• Polymer(Korea)
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• v.39 no.1
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• pp.169-173
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• 2015

Metallocene was supported on the silica, which was functionalized with aminosilanes such as aminopropyltrimethoxysilane (1NS) or N-[3-(trimethoxysilyl)propyl]ethylenediamine (2NS), and ionic liquids such as 1-butyl-4-methylpyridinium chloride (Cl), tributylmethylammonium chloride (Amm), benzyldimethyltetradecylammonium chloride (Ben), 1-butyl-1-methylpyrrolidinium chloride (Pyr), and then ethylene polymerizations were performed. The Zr contents of $SiO_2/1NS/IL/(n-BuCp)_2ZrCl_2$ and $SiO_2/2NS/IL/(n-BuCp)_2ZrCl_2$ were lower than those of only aminosilane-treated silicas. However, the polymerization activity of $SiO_2/1NS/IL/(n-BuCp)_2ZrCl_2$ was higher than that of $SiO_2/1NS/(n-BuCp)_2ZrCl_2$. The polymerization activity of $SiO_2/2NS/IL/(n-BuCp)_2ZrCl_2$ was lower than that of $SiO_2/2NS/(n-BuCp)_2ZrCl_2$ due to much lower Zr content.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.3
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• pp.229-235
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• 2001

Uncooled pyroelectric thin-film (Ba,Sr)TiO$_3$ infrared detectors thermally isolated from Si-substrate by Si$_3$N$_4$/SiO$_2$/Si$_3$N$_4$-membrane have been fabricated, and figures of merit for detectors were examined. The detector at $25^{\circ}C$ in air showed relatively high voltage responsivity of about 168.8 V/W and low specific detectivity of about 2.6$\times$10$^4$cm.Hz$^{1}$2//W at 1 Hz-chopping frequency because of very small signal-to-noise voltage ratio. It could be found that both thermal noise voltage and thermal time constant of the detector were very large by analyzing dependences of output waveforms on chopping frequency and temperature.