• Journal of Sensor Science and Technology
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• v.15 no.1
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• pp.13-19
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• 2006

The micro-gas sensor based on carbon nanotubes (CNTs) was fabricated and its gas sensing characteristics on nitrogen dioxide ($NO_{2}$) have been investigated. The sensor consists of a heater, an insulating layer, a pair of contact electrodes, and CNT-sensing film on a micromachined diaphragm. The heater plays a role in the temperature change to modify sensor operation. Gas sensor responses of CNT-film to $NO_{2}$ at room temperature are reported. The sensor exhibits a reversible response with a time constant of a few minutes at thermal treatment temperature of $130^{\circ}C$.

• Journal of the Korean Institute of Gas
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• v.2 no.4
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• pp.34-41
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• 1998

To oxide film, $A1_2O_3,\;Ta_2O_5$ and $ZrO_2$, coated on stainless steel (SUS410, SUS304) and pure Fe using RF magnetron sputtering method, the corrosion resistance on oxide coatings was studied using electrochemical measurement. Also, the adherence between film and substarte was studied. The adherence index ( $\chi$ ) was determined by the measure of micro hardness test. In this paper, we know that oxide film coated on SUS304 have better corrosion resistance than that coated on SUS410. In oxide film, the difference of corrosion resistance due to crystal structure have not been showed. In evaluating defect area rate of ceramic coated materials, CPCD method can be used effectively. In the micro-hardness test, with $1{\mu}m$ thickness film, it has only one the value of $\chi$. Above $2{\mu}m$ thickness film, however, get another value of $\chi$ as the cracks in film. The oxide film adhere well on the mild materials such as pure steel than high intensity materials like stainless.

• International Journal of Fluid Machinery and Systems
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• v.2 no.1
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• pp.55-60
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• 2009

The present study investigated temperature and thermal stress distributions in a film cooling system with normal injection cooling flow. 3D-numerical simulations using the FEM commercial code ANSYS were conducted to calculate distributions of temperature and thermal stresses. In the simulations, the surface boundary conditions used the surface heat transfer coefficients and adiabatic wall temperature which were converted from the Sherwood numbers and impermeable wall effectiveness obtained from previous mass transfer experiments. As a result, the temperature gradients, in contrast to the adiabatic wall temperature, were generated by conduction between the hot and cold regions in the film cooling system. The gradient magnitudes were about 10~20K in the y-axis (spanwise) direction and about 50~60K in the x-axis (streamwise) direction. The high thermal stresses resulting from this temperature distribution appeared in the side regions of holes. These locations were similar to those of thermal cracks in actual gas turbines. Thus, this thermal analysis can apply to a thermal design of film cooling holes to prevent or reduce thermal stresses.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1433-1435
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• 1997

ZnO shows the properties of wide conductivity variation, high optical transmittance, and excellent piezoelectricity. Using these properties of ZnO, the material applications were extended to sensors, SAW filters, solar cells, and display devices. This paper investigated transmittance influencing factors for thin film ZnO grown by RF magnetron sputtering. The growth rate and structural investigation were carried out in conjunction with optical transmittance characteristics of thin film ZnO. The glass substrate temperature of $175^{\circ}C$ exhibited a preferential crystallization along (002) orientation. Transmittance of ZnO film deposited at the substrate temperature of $175^{\circ}C$ showed higher than 92%. An active sputter gas was investigated with a variation of $O_2$ partial pressure from 0 to 10% in an Ar atmosphere. ZnO film grown in 100% Ar gas shows that a reduced transmittance of 82% at the short wavelengths and decreased resistivity value. As the partial pressure of $O_2$ gas increased, the optical transmittance was increased above 90% at the short wavelengths, however, resistivity was drastically increased to higher than $10^4{\Omega}$-cm.

• Korean Journal of Materials Research
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• v.29 no.12
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• pp.764-773
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• 2019

The gas response characteristic toward C₂H₅OH has been demonstrated in terms of copper-vacancy concentration, hole density, and microstructural factors for undoped/Li(I)-doped CuO thin films prepared by sol-gel method. For the films, both concentrations of intrinsic copper vacancies and electronic holes decrease with increasing calcination temperature from 400 to 500 to 600 ℃. Li(I) doping into CuO leads to the reduction of copper-vacancy concentration and the enhancement of hole density. The increase of calcination temperature or Li(I) doping concentration in the film increases both optical band gap energy and Cu2p binding energy, which are characterized by UV-vis-NIR and X-ray photoelectron spectroscopy, respectively. The overall hole density of the film is determined by the offset effect of intrinsic and extrinsic hole densities, which depend on the calcination temperature and the Li(I) doping amount, respectively. The apparent resistance of the film is determined by the concentration of the structural defects such as copper vacancies, Li(I) dopants, and grain boundaries, as well as by the hole density. As a result, it is found that the gas response value of the film sensor is directly proportional to the apparent sensor resistance.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2675-2685
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• 1994

A study has been conducted to provide the experimental information for the velocity and temperature profiles of steam-air mixutre and to investigate their roles on the film condensation with wavy interface. Saturated gas mixture of steam-air was made to flow through the nearly horizontal$(4.1^{\circ})$ square duct of 0.1m width and 1.56m length at atmospheric pressure, and was condensated on the bottom cold plate. The air mass fraction in the gas mixture was changed from zero(W =0, pure steam) to one(W =1, pure air), and the bulk velocity was varied from 2 to 4 m/s. Water film was injected concurrently to investigate the effect of wavy interface on the condensation. The velocity and temperature profiles were measured by LDA system and thermocouples along the three parameters ; air mass fraction, mixture velocity and film flow rate. The profiles moved toward the interface with increasing steam mass fraction, mixture velocity and film flow rate. The Prandtl and Schmidt numbers were near one in the present experimental range, however there was no complete similarity between the velocity and temperature profiles of gas mixture. And the heat transfer characteristics and interfacial structure were coupled with each other.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.625-627
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• 2002

MgO thin films were deposited on glass and (100) Si substrates by an Arc Ion Plating (AIP) equipment using a magnesium metal target at various oxygen gas flow. In this work, we investigated the relationship between the structural properties and the discharge characteristics of MgO coating layers. X-ray diffraction and AFM have been used to study behaviors of the structure and surface morphology. The optical transmittance and the ion induced secondary electron emission coefficient of the MgO films have been also measured. The resistivity of the deposited MgO films was gradually increased from 0.17 G ohm/${\square}$ to 0.35 G ohm/${\square}$ with the oxygen gas flow. The growth rate of the MgO coating layer was decreased with increasing the oxygen gas flow, while the optical transmittance was improved.

• Journal of the Korean Ceramic Society
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• v.36 no.1
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• pp.55-60
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• 1999

${\beta}$-SiC thin film was deposited on a Si substrate without buffer layer using a single precursor of Hexamethyldisilane (Si2(CH3)6) by chemical vapor deposition method. HCI gas was introduced into hexamethyldisilane /H2 gas mixture, and the feeding schedule of HCI and precursor gases was modified in order to enhance the selectivity of SiC deposition between a Si substrate and a SiO2 mask. The effect of HCI gas on the surface roughness of the SiC film was investigated and typical electrical properties of the SiC film were also investigated by Hall measurement.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.6
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• pp.580-585
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• 2004

Silicon dioxide (SiO$_2$) is widely used as a gate dielectric material for thin film transistors (TFT) and semiconductor devices. In this paper, SiO$_2$ films were grown by APCVD(Atmospheric Pressure chemical vapor deposition) at the high temperature. Experimental investigations were carried out as a function of $O_2$ gas flow ratios from 0 to 200 1pm. This article presents the SiO$_2$ gate dielectric studies in terms of deposition rate, refrative index, FT-IR, C-V for the gate dielectric layer of thin film transistor applications. We also study defect passivation technique for improvement interface or surface properties in thin films. Our passivation technique is Forming Gas Annealing treatment. FGA acts passivation of interface and surface impurity or defects in SiO$_2$ film. We used RTP system for FGA and gained results that reduced surface fixed charge and trap density of midgap value.

• Journal of Sensor Science and Technology
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• v.15 no.5
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• pp.309-316
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• 2006

The $SnO_{2}$ thin film sensors were fabricated by a thermal oxidation method. $SnO_{2}$ thin film sensors were treated in $N_{2}$ atmosphere. The sensors with $O_{2}$ treatment after $N_{2}$ treatment showed 70 % sensitivity for 1 ppm $H_{2}S$ gas, which is higher than the sensors with only $O_{2}$ treatment. The Ni metal was evaporated on Sn thin film on the $Al_{2}O_{3}$ substrate. And the sensor was heated to grow the Sn nanowire in the tube furnace with $N_{2}$ atmosphere. Sn nanowire was thermally oxidized in $O_{2}$ environments. The sensitivity of $SnO_{2}$ nanowire sensor was measured at 500 ppb $H_{2}S$ gas. The selectivity of $SnO_{2}$ nanowire sensor compared with thin film and thick film $SnO_{2}$ was measured for $H_{2}S$, CO, and $NH_{3}$ in this study.