• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.64-65
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• 2005

The structural and electrical properties of the films are investigated as a function of nitrogen/argon ratio at room temperature and at various deposition temperatures. The phase changes as $Ta_2N$ or TaN in the films were observed as nitrogen/argon ratio increases from 3% to 25%. The phase changes were associated with a change in the resistivity and TCR (temperature coefficient of resistance) of the films. TCR values of the films deposited at room temperature and different nitrogen contents were negative, and strongly decreased with the increase in nitrogen/argon ratio. The Ta2N films deposited at nitrogen/argon ratio of 3% show improved TCR values and thermal stability with increasing deposition temperature. The $Ta_2N$ films grown at nitrogen/argon ratio of 3% and the temperature of $200^{\circ}C$ showed a TCR value of -47 $ppm/^{\circ}C$, which is close to near-zero TCR in the range of deposition temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.589-593
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• 2011

[ $SnO_2$ ]nano powders were prepared by solution reduction method using tin chloride($SnCl_2{\cdot}2H_2O$), hydrazine($N_2H_4$) and NaOH. The $SnO_2$ thick films for gas sensors were fabricated by screen printing method on alumina substrates and annealed at $300^{\circ}C$ in air, respectively. XRD patterns of the $SnO_2$ nano powders showed the tetragonal structure with (110) dominant orientation. The particle size of $SnO_2$ nano powders at the ratio of $SnCl_2:N_2H_4$+NaOH= 1:6 was about 60 nm. The sensing characteristics were investigated by measuring the electrical resistance of each sensor in a test box. Sensitivity of $SnO_2$ gas sensor to 5 ppm $CH_4$gas and 5 ppm $CH_3CH_2CH_3$ gas was investigated for various $SnCl_2:N_2H_4$+NaOH proportion. The highest sensitivity to $CH_4$ gas and $CH_3CH_2CH_3$ gas of $SnO_2$ sensors was observed at the $SnCl_2:N_2H_4$+NaOH= 1:8 and $SnCl_2:N_2H_4$+NaOH= 1:6, respectively. Response and recovery times of $SnO_2$ gas sensors prepared by $SnCl_2:N_2H_4$+NaOH= 1:6 was about 40 s and 30 s, respectively.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.25-28
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• 2013

This study presents both experimental and numerical investigation of ignition characteristics of n-heptane and n-butanol mixture. The $O_2$ concentration was fixed to 9-10% to make high exhaust gas recirculation(EGR) rate condition. Experiments were performed using a rapid compression machine. In addition, a numerical study of the ignition delay time was performed using CHEMKIN codes to validate experimental results and predict chemical species after combustion process. The results showed that the ignition delay time increased with increasing n-butanol ratio and the reactivity decreased by low $O_2$ concentration.

• Applied Biological Chemistry
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• v.3
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• pp.25-48
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• 1962

The polysaccharide C prepared from gum tragacanth powder (U. S. P. grade) by the precipitation method with 85% ethanol was a neutral polysaccharide, $[{\alpha}]^{30}_D-72.2$. The polysaccharide C consisted of L-rhamnose, D-xylose, L-arabinose and D-galactose in the molar ratio 2:1:17:9 (Table 1, 2, 3, ). The polysaccharide C was methylated with dimethylsulphate and 40% NaOH, and Purdies regent. The hydrolyzate of fully methlated product ($[{\alpha}]^{22}_D-102$ in chloroform, the methoxy content 40.6%) was composed of 2, 3, 5-tri-O-methyl-L-arabofuranose (I), 3,4-di-O-methyl-L-rhamnopyranose (II), 2,3-di-O-methyl-D-xylose (III), 2,3,4-tri-O-methyl-D-galactopyranose (IV), 2,4-di-O-methyl-L-arabopyranose (?), 2,4-di-O-methyl-D-galactose(VI), 2-O-methyl-D-arabinose (VII), and L-arabopyranose(VIII) (Table 4, 5, and Fig. 4). The first partial hydrolysis (A) of the polysaccharide C with 0.05N-HCl for 4.5 hours at $80-85^{\circ}C$ released only L-arabinose: the second hydrolysis (B) with 0.1N-HCl for 5 hours at $80-85^{\circ}C$, L-arabinose and D-galactose; and the third hydrolysis (C) with 0.3N-HCl at $90-95^{\circ}C$ in sealed tube, L-rhamnose, D-xylose, L-arabinose and D-galactose. From the unhydrolyzate A' were found L-rhamnose, D-xylose, L-arabinose, and D-galactose; from B' L-rhamnose, d-xylose, L-arabinose and D-galactose; and from C' D-xylose and D-galactose respectively (Table 6). The periodate consumption and formic acid production of the polysaccharide C were measured at various time intervals. After 120 hours periodat was consumed by 1.23 mole per $C_5H_8O_4$ and formic acid was produced 0.78 mole per $C_5H_8O_4$ (Table 7). Although a definite chemical structure for this polysaccharide C may not be formulated, experimental data, especially, from methylation, partial hydrolysie and determination of its molar ratio, and periodate analysis showed that the polysaccharide C is a highly branched polysaccharide and would be constructed of galactoaraban as a main chain residue and L-arabofuranose, D-galactopyranosyl $(1{\rightarrow}1)$-L-arabofuranose, D-xylopyranosyl $(1{\rightarrow}2)$-L-rhamnopyranosyl $(1{\rightarrow}1)$-L-arabofuranose, and L-rhamnopyranosyl $(1{\rightarrow}1)$-arabofuranose, and D-galactopyranosyl-$(1{\rightarrow}2)$-L-arabopyranosyl-$(1{\rightarrow}1)$-I-arabofuranose as a branch chain or end group (page 21).

• Journal of Korean Vacuum Science & Technology
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• v.2 no.2
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• pp.122-132
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• 1998

Characteristics of inductively coupled Cl2/O2 and Cl2/N2 plasmas and their effects on the formation of submicron deep trench etching of single crystal silicon have been investigated using Langmuir probe, quadrupole mass spectrometer (QMS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), Also, when silicon is etched with oxygen added chlorine plasmas, etch products recombined with oxygen such as SiClxOy emerged and Si-O bondings were found on the etched silicon surface. However, when nitrogen is added to chlorine, no etch products recombined with nitrogen nor Si-N bondings were found on the etched silicon surface. When deep silicon trenches were teached, the characteristics of Cl2/O2 and Cl2/N2 plasmas changed the thickness of the sidewall residue (passivation layer) and the etch profile. Vertical deep submicron trench profiles having the aspect ratio higher than 5 could be obtained by controlling the thickness of the residue formed on the trench sidewall using Cl2(O2/N2) plasmas.

• Journal of environmental and Sanitary engineering
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• v.15 no.1
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• pp.95-101
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• 2000

This study was investigated to the reaction of alumina sintering with alkaline. The soluble $NaAlO_2$ was made after the commercial ${\alpha}-Al_2O_3$ was calcinated with NaOH. The reaction of alumina was carried out to be based on the effects of calcination temperature, time, and the mixing ratio of ${\alpha}-Al_2O_3/NaOH$. The alumina was calcined over $500^{\circ}C$ with NaOH powder after it was sieved with 170/270 mesh. The calcined alumina with NaOH powder was dissolved into $25^{\circ}C$ distilled water and filtrated, and HCI was added to adapt pH 6.5~7.5. The residue was separated with vacuum pump for filtration after it was adapted to proper pH, and aluminum compound was precipitated with $Al(OH)_3$. The investigation was carried out with the variables; the calcination temperature($500-900^{\circ}C$), the calcination time (30~90 min), and the concentration of HCI when leaching(0.5~3.0N) respectively. In this investigation, the main product of ${\alpha}-Al_2O_3$ and NaOH was $NaAlO_2$ and the maximum conversion ratio was 91.4% under the optimum conditions as followed ; the ratio of NaOH/${\alpha}-Al_2O_3$ was 1.5 and the calcination conditions were $800^{\circ}C$ and 90 min.

• Journal of the Korean Ceramic Society
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• v.28 no.12
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• pp.961-968
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• 1991

The nature and composition of the surfaces of silicon nitride and β-Sialon powders were investigated using high voltage and high resolution transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). β-Sialon powder was produced from Hadong kaolin by the carbothermic reduction and simultaneous nitridation. XPS showed that Al was contained in the surface of β-Sialon powder besides Si, N and O components, which is different from that of silicon nitride. It was supposed that Al in the surface of β-Sialon was bonded with oxygen from the oxygen-nitrogen ratio and the measurement of Al 2p binding energies. After both silicon nitride and β-Sialon powders were oxidized at 800℃ for 24h in air, nitrogen didn't exist in the surfaces and the depth of the oxide layer increased. The measurement of Si 2p binding energies showed that the chemical shifts occurred from Si3N2O and/or Si2N2O to SiO2 phase.

• Korean Journal of Materials Research
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• v.7 no.2
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• pp.114-120
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• 1997

Perovskite $BaTiO_3$ thin films on stainless steel substrate were prepared by using electrochemical reduction method in solution of $TiCl_4\;and\;Ba(N0_3)_2$. According to current density and electrolysis time. the morphology and thickness of film were varied. Ra/'Ti atomic ratio in $BaTiO_3$ film was controlled by Ha/Ti atomic ratio in solution. Although the excess $TiO_2{\cdot}nH_2O$ film was coated in initial stage of electrolysis. UiilTi atomic ratio in film was nearly constant in later stage. $BaTiO_3$ film precursor was obtained under the condition of $1OmA/cm^2$ current density and Smin electrolysis time. $BaTiO_2$ thin films with perovskite phase were formed 11,. the heat treatment above $500^{\circ}$.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.1
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• pp.31-35
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• 2020

This study demonstrates metal-oxide based memtransistor device and the gate tunable memristive characteristic using atomic layer deposition (ALD) and ZnO n-type oxide semiconductor. We fabricated a memtransistor device having channel width 70 ㎛, channel length 5 ㎛, back gate, using 40 nm thick ZnO thin film, and measured gate-tunable memristive characteristics at each gate voltage (50V, 30V, 10V, 0V, -10V, -30V, -50V) under humidity of 40%, 50%, 60%, and 70% respectively, in order to investigate the relation between a memristive characteristic and hydrogen doping effect on the ZnO memtransistor device. The electron mobility and gate controllability of memtransistor device decreased with an increase of humidity due to increased electron carrier concentration by hydrogen doping effect. The gate-tunable memristive characteristic was observed under humidity of 60% 70%. Resistive switching ratio increased with an increase of humidity while it loses gate controllability. Consequently, we could obtain both gate controllability and the large resistive switching ratio under humidity of 60%.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.86.2-86.2
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• 2012

산화금속은 높은 결정성, quantum size effect, 높은 투과도, 대기중의 안정도 등과 같은 탁월한 성질들로 인하여 오늘날 실리콘의 대체물로서 많은 연구가 보고되고 있다. 이러한 금속산화물의 크기와 모양을 조절하며 대량 생산하기 위한 합성방법으로 가수분해, 금속양이온 응축법과 같은 다양한 수용액상 방법이 연구되고 있다. 하지만 2차원 단일 층에 나노물질을 정렬하고 전기적 접합을 형성하는 것이 매우 어렵다는 점 때문에 나노물질을 기판 위에 자유롭게 성장시키는 방법에 대해서는 아직 많이 보고 되어있지 않다. 본 연구에서 저온의 수용액에서 1차원의 나노막대가 2차원의 스피넬 구조 위에 heteroepotaxial 접합을 이루며 성장시키는 방법을 이용하였다. P-n접합 형성을 위하여 (0001)방향으로 배향된 n-type ZnO 나노막대를 (111)방향의 p-type Co3O4 나노플레이트 위에 성장시킨 구조를 제작하였으며 이를 바탕으로 다이오드소자를 제작하여 ideal factor, turn-on voltage, rectifying ratio등의 전기적 특성을 평가하였다.