• 한국식품과학회지
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• 제30권2호
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• pp.356-362
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• 1998

된장의 숙성기간을 예측하기 위하여 6개의 metal oxide sensor로 구성된 휴대용 전자코를 이용하였다. Aspergillus oryzae를 사용하여 담금한 된장은 각각 $15,\;20\;25^{\circ}C$에서 숙성시켰다. 전자코에 의한 감응도 변화량은 숙성기간에 따라 온도가 높아짐에 따라 크게 감소되었으며 센서 #3과 #4는 된장의 숙성정도와 기간간에 높은 상관관계를 보여주었다$(r^2=0.71{\sim}0.95)$. 그리고 숙성기간중 생성되는 아미노태질소와 전자코의 감응도 변화간에도 상관관계를 나타내어 휴대용 전자코로 된장의 숙성기간을 예측할 수 있었다.

• 한국재료학회지
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• 제26권2호
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• pp.84-89
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• 2016

We present the rectifying and nitrogen monoxide (NO) gas sensing properties of an oxide semiconductor heterostructure composed of n-type zinc oxide (ZnO) and p-type copper oxide thin layers. A CuO thin layer was first formed on an indium-tin-oxide-coated glass substrate by sol-gel spin coating method using copper acetate monohydrate and diethanolamine as precursors; then, to form a p-n oxide heterostructure, a ZnO thin layer was spin-coated on the CuO layer using copper zinc dihydrate and diethanolamine. The crystalline structures and microstructures of the heterojunction materials were examined using X-ray diffraction and scanning electron microscopy. The observed current-voltage characteristics of the p-n oxide heterostructure showed a non-linear diode-like rectifying behavior at various temperatures ranging from room temperature to $200^{\circ}C$. When the spin-coated ZnO/CuO heterojunction was exposed to the acceptor gas NO in dry air, a significant increase in the forward diode current of the p-n junction was observed. It was found that the NO gas response of the ZnO/CuO heterostructure exhibited a maximum value at an operating temperature as low as $100^{\circ}C$ and increased gradually with increasing of the NO gas concentration up to 30 ppm. The experimental results indicate that the spin-coated ZnO/CuO heterojunction structure has significant potential applications for gas sensors and other oxide electronics.

• Advances in nano research
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• 제9권1호
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• pp.25-32
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• 2020

In this work, we report the use of caffeine as an alternative source of nitrogen to successfully dope graphene (quaternary 400.6 eV and pyridinic at 398 eV according XPS), as well as the growth of silver nanowires (in-situ) in the surface of nitrogen doped graphene (NG) sheets. We used the improved graphene oxide method (IGO), chemical reduction of graphene oxide (GOx), and impregnation with caffeine as source of nitrogen for doping and subsequently, silver nanowires (NW) grow in the surface by the reduction of silver salts in the presence of NG, achieving a numerous of growth of NW in the graphene sheets. As supporting experimental evidence, the samples were analyzed using conventional characterization techniques: SEM-EDX, XRD, FT-IR, micro RAMAN, TEM, and XPS.

• 한국표면공학회지
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• 제54권5호
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• pp.260-266
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• 2021

Synthesizing low-dimensional structures of oxide semiconductors is a promising approach to fabricate highly efficient gas sensors by means of possible enhancement in surface-to-volume ratios of their sensing materials. In this work, vertically aligned zinc oxide (ZnO) nanorods are successfully synthesized on a transparent glass substrate via seed-mediated hydrothermal synthesis method with the use of a ZnO nanoparticle seed layer, which is formed by thermally oxidizing a sputtered Zn metal film. Structural and optical characterization by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy reveals the successful preparation of the ZnO nanorods array of the single hexagonal wurtzite crystalline phase. From gas sensing measurements for the nitrogen dioxide (NO₂) gas, the vertically aligned ZnO nanorod array is observed to have a highly responsive sensitivity to NO₂ gas at relatively low concentrations and operating temperatures, especially showing a high maximum sensitivity to NO₂ at 250 ℃ and a low NO₂ detection limit of 5 ppm in dry air. These results along with a facile fabrication process demonstrate that the ZnO nanorods synthesized on a transparent glass substrate are very promising for low-cost and high-performance NO₂ gas sensors.

• 한국표면공학회지
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• 제56권4호
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• pp.219-226
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• 2023

Utilizing low-dimensional structures of oxide semiconductors is a promising approach to fabricate relevant gas sensors by means of potential enhancement in surface-to-volume ratios of their sensing materials. In this work, vertically aligned cupric oxide (CuO) nanorods are successfully synthesized on a transparent glass substrate via seed-mediated hydrothermal synthesis method with the use of a CuO nanoparticle seed layer, which is formed by thermally oxidizing a sputtered Cu metal film. Structural and optical characterization by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy reveals the successful preparation of the CuO nanorods array of the single monoclinic tenorite crystalline phase. From gas sensing measurements for the nitrogen monoxide (NO) gas, the vertically aligned CuO nanorod array is observed to have a highly responsive sensitivity to NO gas at relatively low concentrations and operating temperatures, especially showing a high maximum sensitivity to NO at 200 ℃ and a low NO detection limit of 2 ppm in dry air. These results along with a facile fabrication process demonstrate that the CuO nanorods synthesized on a transparent glass substrate are very promising for low-cost and high-performance NO gas sensors.

• Transactions on Electrical and Electronic Materials
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• 제12권5호
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• pp.200-203
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• 2011

In this research, nitrogen (N)-doped zinc oxide (ZnO) thin films have been grown on a sapphire substrate by dielectric barrier discharge (DBD) in pulsed laser deposition (PLD). DBD has been used as an effective way for massive in-situ generation of N-plasma under conventional PLD process conditions. Low-temperature photoluminescence spectra of N-doped ZnO thin films provided near-band-edge emission after a thermal annealing process. The emission peak was resolved by Gaussian fitting and showed a dominant acceptor-bound excitation peak ($A^{\circ}X$) that indicated acceptor doping of ZnO with N. The acceptor binding energy of the N acceptor was estimated to be approximately 145 MeV based on the results of temperature-dependent photoluminescence (PL) measurements.

• Composites Research
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• 제29권4호
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• pp.132-137
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• 2016

Based on mussel-inspired polydopamine (PDA), a novel technique to fabricate carbon nanowire (CNW) arrays is presented for a possible use of porous carbon electrode in electrochemical energy storage applications. PDA can give more porosity and nitrogen-doping effect to carbon electrodes, since it has high graphitic carbon yield characteristic and rich amine functionalities. Using such outstanding properties, the applicability of PDA for electrochemical energy storage devices was investigated. To achieve this, the decoration of the CNW arrays on carbon fiber surface was performed to increase the surface area for storage of electrical charge and the chemical active sites. Here, zinc oxide (ZnO) nanowire (NW) arrays were hydrothermally grown on the carbon fiber surface and then, PDA was coated on ZnO NWs. Finally, high temperature annealing was performed to carbonize PDA coating layers. For higher energy density, manganese oxide ($MnO_x$) nanoparticles (NPs), were deposited on the carbonized PDA NW arrays. The enlarged surface area induced by carbon nanowire arrays led to a 4.7-fold enhancement in areal capacitance compared to that of bare carbon fibers. The capacitance of nanowire-decorated electrodes reached up to $105.7mF/cm^2$, which is 59 times higher than that of pristine carbon fibers.

• 전기학회논문지
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• 제59권11호
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• pp.2016-2020
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• 2010

Indium-zinc-oxide (IZO) films were deposited at room temperature via RF sputtering with varying the flow rate of additive nitrogen gas ($N_2$). Thin film transistors (TFTs) with an inverted staggered configuration were fabricated by employing the various IZO films, such as $N_2$-added and pure (i.e., w/o $N_2$-added), as active channel layers. For all the deposited IZO films, effects of additive $N_2$ gas on their deposition rates, electrical resistivities, optical transmittances and bandgaps, and chemical structures were extensively investigated. Transfer characteristics of the IZO-based TFTs were measured and characterized in terms of the flow rate of additive $N_2$ gas. The experimental results indicated that the transistor action occurred when the $N_2$-added (with $N_2$ flow rate of 0.4-1.0 sccm) IZO films were used as the active layer, in contrast to the case of using the pure IZO film.

• 한국재료학회지
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• 제19권1호
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• pp.37-43
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• 2009

Silicon dioxide as gate dielectrics was grown at $400^{\circ}C$ on a polycrystalline Si substrate by inductively coupled plasma oxidation using a mixture of $O_2$ and $N_2O$ to improve the performance of polycrystalline Si thin film transistors. In conventional high-temperature $N_2O$ annealing, nitrogen can be supplied to the $Si/SiO_2$ interface because a NO molecule can diffuse through the oxide. However, it was found that nitrogen cannot be supplied to the Si/$SiO_2$ interface by plasma oxidation as the $N_2O$ molecule is broken in the plasma and because a dense Si-N bond is formed at the $SiO_2$ surface, preventing further diffusion of nitrogen into the oxide. Nitrogen was added to the $Si/SiO_2$ interface by the plasma oxidation of mixtures of $O_2/N_2O$ gas, leading to an enhancement of the field effect mobility of polycrystalline Si TFTs due to the reduction in the number of trap densities at the interface and at the Si grain boundaries due to nitrogen passivation.

• 한국연소학회지
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• 제13권1호
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• pp.10-16
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• 2008

Numerical simulations of freely propagating premixed flames burning mixtures of methane and chlorinated hydrocarbons in fuel are performed at atmospheric pressure in order to understand the effect of chlorinated hydrocarbons on the formation of nitrogen oxide. A detailed chemical reaction mechanism is used, the adopted scheme involving 89 gas-phase species and 1017 elementary forward reaction steps. Chlorine atoms available from chlorinated hydrocarbons inhibit the formation of nitrogen oxides by lowering the concentration of radical species. The reduction of NO emission index calculated with thermal or prompt NO mechanism is not linear and is probably related to the saturation effect as $CH_3Cl$ addition is increased, In the formation or consumption of nitrogen oxide, the $NO_2$ and NOCl reactions play an important role in lean flames while the HNO reactions do in rich flames. The molar ratio of Cl to H in fuel has an effect on the magnitude of NO emission index.