• Korean Journal of Materials Research
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• v.15 no.4
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• pp.275-280
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• 2005

The growth of hafnium oxide thin films by atomic layer deposition was investigated in the temperature range of $175-350^{\circ}C$ using $Hf[N(CH_3)_2]_4\;and\;O_2$ as precursors. A self-limiting growth of $0.6\AA/cycle$ was achieved at the substrate temperature of $240-280^{\circ}C$. The films were amorphous and very smooth (0.76-0.80 nm) as examined by X-ray diffractometer and atomic force microscopy, respectively. X-ray photoelectron spectroscopy analysis showed that the films grown at $300^{\circ}C$ was almost stoichiometric. Electrical measurements performed on $MoW/HfO_2$(20 nm)/Si MOS structures exhibited high dielectric constant$(\~17)$ and a remarkably low leakage current density of at an applied field of $1.5-6.2\times10^{-7}A/cm^2$ MV/cm, probably due to the stoichiometry of the films.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.238-238
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• 2011

Ion sensitive field effect transistor (ISFET)는 용액의 이온 농도를 측정하는 반도체 센서로, 1970년 Bergveld에 의해 처음으로 제안되었다. ISFET가 제안된 이래로, 제조공정이 간단하고 감지막의 감지 특성 평가가 용이한 electrolyte-insulator-semiconductor (EIS) pH센서 또한 지속적으로 연구되었다. EIS pH센서는 작은 소자 크기, 견고한 구조, 빠른 응답속도와 CMOS공정과의 호환성이 좋다는 장점이 있다. EIS 또는 ISFET 센서를 이용하여 생물학적 요소의 신호 감지 특성을 평가함에 있어 소자의 signal to noise 비율이 우수해야 한다. EIS pH센서의 높은 signal to noise 비율을 얻기 위해, 소자의 표면적을 증가시키거나 감지막으로 유전상수가 높은 물질을 사용하여 출력 특성을 향상시켜야 한다. 본 연구에서는 trench구조와 SiO2/HfO2/Al2O3 (OHA) 적층 감지막을 갖는 EIS pH센서를 제작하여 출력 특성을 증가시키는 실험을 실시하였다. 120 nm, 380 nm, 780 nm의 다양한 깊이를 가진 trench를 형성하였으며, trench 깊이에 따른 출력특성을 비교하였다. 또한, 제작된 EIS 소자의 pH감지 특성을 분석하였다. 제작된 EIS소자의 감지막 중 SiO2는 Si와 high-k물질의 계면 상태를 보완하기 위한 완충막으로 성장되었고, HfO2는 높은 유전상수를 가지고 있어 signal to noise 비율을 향상시키는 물질로 증착되었다. 최종적으로 Al2O3는 pH용액과의 화학적 손상을 막기 위한 물질로 증착되었다. 실험 결과, trench 깊이가 깊어질수록 출력값이 증가하였고 이는 signal to noise 비율이 향상되는 것을 의미한다. 결론적으로 trench 형성을 통한 표면적 증가와 high-k물질을 적층한 감지막으로 인해 높은 출력 특성을 갖는 우수한 EIS 바이오센서를 제작할 수 있었다.

• Korean Journal of Materials Research
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• v.11 no.1
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• pp.3-7
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• 2001

$M\"{o}ssbauer$ spectra of the $Ni_{1+x}Ti_xFe_{2-2x}O_4$ systems ($0{\leqq}x{\leqq}0.7$), which appear as single phase spinel structure, were examined at RT. The $M\"{o}ssbauer$ spectra reveal two sextet for $0{\leqq}x{\leqq}0.3$, two sextet and a doublet for $0.4{\leqq}x{\leqq}0.6$, and a doublet for x=0.7 As x increases, the area ratio of B-site and A-site($A_B/A_A$) of the sextet decreases, and the area ratio of the doublet and the total areas($A_{doublet}/A_{tot.}$) increases. The isomer shift(I.S.) of A-site slightly increases and magnetic hyperfine fields($H_{hf}$) of two sites decrease as the increasing x. From these results, we have obtained the cation distributions of the samples and concluded that the increasing x leads to the decrease of covalency of $Fe^{3+}-O^{2-}$ bond in A-sites and A-B superexchange interactions.eractions.

• Analytical Science and Technology
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• v.14 no.4
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• pp.317-323
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• 2001

Dissolution procedures of Monsanto catalyst which has been used to produce acrylronitrile by ammoxidation of propylene have been studied. Optimum dissolution condition of the catalyst supported on silica was obtained by microwave digestion system with mixed of HCl, HF and $H_2O_2$. When a safety device was activated by increased pressure in microwave vessel, Bi, Fe, Mo, Sb and U were not volatilized even though silica was volatilized as $SiF_4$. Quantification results by this method were $SiO_2$ $50.5{\pm}0.4%$, $Sb_2O_3$ $29.6{\pm}0.6%$, $UO_2$ $10.2{\pm}0.1%$, $Fe_2O_3$ $6.1{\pm}0.1%$, $MoO_3$ $0.73{\pm}0.01%$ and $Bi_2O_3$ $0.49{\pm}0.01%$ by ICP-AES and the relative error was within ${\pm}10%$ except bismuth.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.154-158
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• 2015

In this study, the catalytic activity of ${\gamma}-Al_2O_3$ was investigated for the decomposition of $NF_3$. Reactions for $NF_3$ decomposition were carried out in the range of reaction temperature of $330{\sim}730^{\circ}C$ and GHSV of $3,000{\sim}15,000mL/g-cat{\cdot}h$ in a fixed-bed catalytic reactor system. Thermal decomposition of $NF_3$ was also performed in order to compare with the catalytic decomposition of $NF_3$. The conversion of $NF_3$ by the catalytic decomposition at $400^{\circ}C$ was four times higher than that of the thermal decomposition. It was confirmed that the reaction behavior of $NF_3$ over ${\gamma}-Al_2O_3$ exhibited two reaction pathways in the presence of steam. Fluorine in $NF_3$ over ${\gamma}-Al_2O_3$ was chemically absorbed to $AlF_3$ by the gas-solid reaction in the absence of steam. The catalytic decomposition of $NF_3$ occurred by hydrolysis with steam. It was also confirmed by FT-IR analysis that $NF_3$ was completely decomposed to NOx and HF above $500^{\circ}C$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.171-171
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• 2003

공정기술의 향상으로 DRAM(dynamic random acess memory)의 고집적화가 이루어지고 있으며, 각 개별소자 및 셀 영역의 점유면적의 감소가 요구되어지고 있다. 따라서 기존에 사용하던 NO (Si$_3$N$_4$/SiO$_2$)박막보다 유전율이 높은 고유전물질에 대한 연구가 진행되고 있다. Ta$_2$O$_{5}$, $Y_2$O$_3$, HfO$_2$, ZrO$_2$,Nb$_2$O$_{5}$, BaTiO$_3$, SrTiO$_3$ 및 (BaSr)TiO등이 고유전물질로 연구되고 있는데 그 중 공정의 안정성, 누설전류의 우수성으로 인해 Ta$_2$O$_{5}$이 많이 연구되고 있다. 본 실험에서는 TiO$_2$가 8 mol%가 첨가된 Ta$_2$O$_{5}$의 열처리 온도에 따른 전기적, 유전특성을 살펴보려고 한다살펴보려고 한다

• The Journal of Advanced Prosthodontics
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• v.12 no.4
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• pp.189-196
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• 2020

PURPOSE. The aim of the present study was to investigate the effects of surface treatments on the bond strengths between polymer-containing restorative materials and two dual-cure resin cements. MATERIALS AND METHODS. In the present study, rectangular samples prepared from Lava Ultimate (LU) and Vita Enamic (VE) blocks were used. The specimen surfaces were treated using CoJet sandblasting, 50 ㎛ Al₂O₃ sandblasting, % 9 HF (hydrofluoric) acid, ER,Cr:YSGG laser treatment, and Z-Prime. Dual-cure resin cements (TheraCem and 3M RelyX U 200) were applied on each specimen's treated surface. A micro-tensile device was used to evaluate shear bond strength. Statistical analysis was performed using the SAS 9.4v3. RESULTS. While the bond strength using TheraCem with LU or VE was not statistically significant (P=.164), the bond strength using U200 with VE was statistically significant (P=.006). In the TheraCem applied VE groups, Z-Prime and HF acid were statistically different from CoJet, Laser, and Sandblast groups. In comparison of TheraCem used LU group, there was a statistically significant difference between HF acid and other surface treatments. CONCLUSION. The bonding performance between the restorative materials and cements were material type-dependent and surface treatment had a large effect on the bond strength. Within the limitations of the study, the use of both U200 and TheraCem may be suggested if Z-prime was applied to intaglio surfaces of VE. The cementation of LU using TheraCem is suitable after HF acid conditioning of the restoration surfaces.

• Journal of the Korean Chemical Society
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• v.26 no.5
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• pp.320-325
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• 1982

Utilyzing the solution prepared for the sulfur determination, the amounts of iron, copper and cobalt in the sulfide ore were determined by X-ray fluorescence spectrometry. The samples were dissolved with the mixed solutions of ,$Br_2\;and\;HNO_3$ and a major constituent of $SiO_2$was repelled from the solution by HF treatment several times. The analytical results agreed with the data obtained by conventional methods within ${\pm}$1.5% for Fe of the range of 20 to 50%, ${\pm}$1.0% for Cu of 10 to 15%, and ${\pm}$0.4% for Co of 1 to 5%. The present method was tolerably found to be reproducible.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.685-688
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• 2009

Surface Texturing is very important process for high cell efficiency in crystalline silicon solar cell. Anisotropic texturing with an alkali etchant was known not to be able to produce uniform surface morphology in multi-crystalline silicon (mc-Si), because of its different etching rate with random crystal orientation. In order to reduce surface reflectance of mc-Si wafer, the general etching tendency was studied with HF/HN$O_3$/De-ionized Water acidic solution. And the surface structures of textured mc-Si in various HF/HN$O_3$ ratios were compared. The surface morphology and reflectance of textured silicon wafers were measured by FE-SEM and UVvisible spectrophotometer, respectively. We obtained average reflectance of $16{\sim}19$% for wavelength between 400 nm and 900 nm depending on different etching conditions.

• Journal of the Korean Ceramic Society
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• v.21 no.4
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• pp.327-332
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• 1984

Proper amount of $Al_2O_3$ must be added to increase the yield of mullite which is formed from free silica decomposed from kaolin. The previous study has suggested that Al powder may be a good $Al_2O_3$ supply source at 1400~150$0^{\circ}C$. In this study the application of Al powder is discussed about its mullitization behavior in the higher temperature range of 1500~175$0^{\circ}C$ the results of which compared with those obtained from the reactive $Al_2O_3$ and activated $Al_2O_3$. The oxdation and reaction stages of Al powder were analyzed by DTA crystal growth andmorphology of the mullite were observed by SEM and the yields of the mullite were compared according to their solubilities in HF solution.