• 센서학회지
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• 제10권4호
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• pp.222-231
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• 2001

$SnO_2$의 물성을 $Fe_2O_3$ 첨가량, 산소분압, CO 기체농도, 그리고 온도의 함수로서 관찰하였다. 시편은 후막인쇄 기법으로 알루미나 기판 위에 제조하였다. $700^{\circ}C$/6h 소성한 시편들의 $Fe_2O_3$첨가량에 따른 미세구조와 입자분포의 차이는 거의 없었다. $Fe_2O_3$를 첨가하지 않은 $SnO_2$의 전기적 성질은 소성온도가 낮은 경우와 산소분압이 낮은 경우에 전도성이 높게 측정되었다. $Fe_2O_3$를 첨가한 $SnO_2$의 전도성은 측정온도 증가로 증가하지만 $Fe_2O_3$ 첨가량 증가로 전도성은 감소하였다. 산소분압 의존성은 $Fe_2O_3$ 첨가로 감소하였다. CO 가스에 대한 기체 센서 특성 중 감도는 $350^{\circ}C$, 0.1 mol% $Fe_2O_3$를 첨가한 경우에 가장 높았고, 재현성 및 응답성도 양호하게 나타났다.

• Journal of Advanced Marine Engineering and Technology
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• 제24권6호
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• pp.61-69
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• 2000

Indium-Tin Oxide (ITO) films were prepared on the commercial glass substrate by the Magnetron Sputtering method. The target was a 90wt.% $In_2O_3$-10wt.% $SnO_2$with 99.99% purity. The ITO films deposited by changing the partial pressure of oxygen gas ($O_2$/(Ar+$O_2$)) of 2, 3 and 5% as well as by changing the substrate temperature of $300^{\circ}C$ or $500^{\circ}C$. The influence of substrate pre-annealing and pre-cleaning on the quality of ITO film were examined, in which the substrate temperature was $500^{\circ}C$ and oxygen partial pressure was 3%. The characteristics of films were examined by the 4-point probe, Hall effect measurement system, SEM, AFM, Spectrophotometer, and X-ray diffraction. The optimum ITO films have been obtained when the substrate temperature is $500^{\circ}C$ and oxygen partial pressure is 3%. At optimum condition, the film showed transmittance of 81%, sheet resistivity of $226\Omegatextrm{cm}^2$, resistivity($\rho$) of $5.4\times10^{-3}\Omega$cm, carrier concentration of $1.0\times10^{19}cm^{-3}$, and carrier mobility of $150textrm{cm}^2$Vsec. From XRD spectrum, c(222) plane was dominant in the case of substrate temperature at $300^{\circ}C$, without regarding to oxygen partial pressure. However, in the case of substrate temperature at $500^{\circ}C$, c(400) plane was grown together with c(222) plane, only for oxygen partial pressure of 2 and 3%. In both case of chemical and ultrasonic cleaning without pre-annealing the substrate, it showed much almost same sheet resistivity, resistivity($\rho$), transmittance, carrier concentration, and carrier mobility. In case of $500^{\circ}C$/60min pre-annealing before ITO film deposited, both transimittance and carrier mobility are better than no pre-annealing, because pre-annealing is supposed to remove alkari ions diffusion from substrate. ITO film deposited on the Corning 0080 sybstrate showed a little bit better sheet resistivity, resistivity($\rho$), transimittance, carrier concentration than the film deposited on commercial glass. But no differences between Corning substrate and pre-annealed commercial glass substrate are found.

• Journal of Electrical Engineering and Technology
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• 제6권4호
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• pp.539-542
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• 2011

Thin-film transistors (TFTs) are fabricated using an amorphous indium gallium zinc oxide (a-IGZO) channel layer by rf-magnetron sputtering. Oxygen partial pressure significantly changed the transfer characteristics of a-IGZO TFTs. Measurements performed on a-IGZO TFT show the change of threshold voltage in the transistor channel layer and electrical properties with varying $O_2$ ratios. The device performance is significantly affected by adjusting the $O_2$ ratio. This ratio is closely related with the modulation generation by reducing the localized trapping carriers and defect centers at the interface or in the channel layer.

• 한국수소및신에너지학회논문집
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• 제13권2호
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• pp.119-126
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• 2002

The methanol partial oxidation using commercial $CuO/ZnO/Al_2O_3$ catalysts in a plug flow reactor was studied in the temperature range of $200{\sim}250^{\circ}C$ at atmospheric pressure, It was achieved the high activities by Cu-based catalysts and the selectivity of $CO_2$/$H_2$ was 100% when $O_2$ was fully convened. The reactivity changes and their hysteresis with increasing/decreasing temperatures were observed due to the chemical state differences between the oxidation and the reduction on the Cu surface, It was suggested as the two-step reaction: the complete oxidation and the following steam reforming for methanol, which was indicated by the distributions of final products vs. the residence time. In addition, the complete oxidation step was shown to be extremely fast and the total reaction rate can be controlled by the steam reforming reaction.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 영호남학술대회 논문집
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• pp.222-232
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• 2000

The relationship between carrier electron concentration(n) and atmosphere oxygen partial pressure($P_{O_2}$ for pure ZnO calculated by the mass-action law, well-known as n ${\propto}P^{-1/m}_{O_2}$ where m = 4 or 6 for the single or the double ionization of the native donor defects due to its nonstoichiometry, respectively, is found in competition with the calculation result on the basis that the total defect concentration is the sum of those of unionized and ionized defects. Definitively, it is found inconsistent with the calculation result by employing the Fermi-Dirac(FD) statistics for their ionization processes. By application of the FD statistics law to the ionization while assuming the defect formation is still ruled by the mass-action law, the calculation results shows the concentration is proportional to $P^{-1/2}_{O_2}$ whenever they ionize singly and/or doubly. Conclusively we would like to propose the new theoretical relation n ${\propto}P^{-1/m}_{O_2}$ because the ionization processes of donors in ZnO should be treated with the electronoccupation probability at localized quantum states in its forbidden band created by the donor defects, i.e. the FD statistics

• Bulletin of the Korean Chemical Society
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• 제13권3호
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• pp.248-252
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• 1992

$ZrO_2-dopedYb_2O_3solid$ solutions containing 1, 3, 5, 7 and 9 mol% $ZrO_2were$ synthesized from spectroscopically pure $Yb_2O_3$ and $ZrO_2$ powders and found to be rare earth C-type structure by XRD technique. Electrical conductivities were measured as a function of temperatures from 700 to $1050^{\circ}C$ and oxygen partial pressures from 1${\times}$$10^-5$ to 2${\times}$ $10^-1$atm. The electrical conductivities depend simply on temperature and the activation energies are determined to be 1.56-1.68 $_eV$. The oxygen partial pressure dependence of the electrical conductivity shows that the conductivity increases with increasing oxygen partial pressure, indicating p-type semiconductor. The $PO_2$ dependence of the system is nearly power of 1/4. It is suggested from the linearity of the temperature dependence of electrical conductivity and only one value of 1/n that the solid solutions of the system have single conduction mechanism. From these results, it is concluded that the main defects of the system are negatively doubly charged oxygen interstitial in low. $ZrO_2doping$ level and negatively triply charged cation vacancy in high doping level and the electrical conduction is due to the electronic hole formed by the defect structure.

• 소성∙가공
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• 제28권1호
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• pp.43-48
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• 2019

Aluminum nitride (AlN) is used by the semiconductor industry, and is a compound that is required when manufacturing high thermal conductivity. The AlN films with c-axis orientation and thermal conductivity characteristic were deposited by using the Pulsed Laser Deposition (PLD). The AlN thin films were characterized by changing the deposition conditions. In particular, we have researched the AlN thin film deposited under optimal conditions for growth atmosphere. The epitaxial AlN films were grown on sapphire ($c-Al_2O_3$) single crystals by PLD with AlN target. The AlN films were deposited at a fixed temperature of $650^{\circ}C$, while conditions of nitrogen ($N_2$) pressure were varied between 0.1 mTorr and 10 mTorr. The quality of the AlN films was found to depend strongly on the $N_2$ partial pressure that was exerted during deposition. The X-ray diffraction studies revealed that the integrated intensity of the AlN (002) peak increases as a function the corresponding Full width at half maximum (FWHM) values decreases with lowering of the nitrogen partial pressure. We found that highly c-axis orientated AlN films can be deposited at a substrate temperature of $650^{\circ}C$ and a base pressure of $2{\times}10^{-7}Torr$ in the $N_2$ partial pressure of 0.1 mTorr. Also, it is noted that as the $N_2$ partial pressure decreased, the thermal conductivity increased.

• 대한치과보철학회지
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• 제21권1호
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• pp.59-66
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• 1983

Distal extension partial dentures are supported by both the relatively rigid teeth and the resilient mucosa. So impression techniques of residual alveolar ridge in case of distal extension partial denture have particular importance in order to broad distribution of the masticatory force. McLean recognized the need for recording the tissues supporting distal extension partial denture base in functional form to equalize the resilient and non-resilient support, and this was called functional impression. Many investigators proposed various techniques of the functional impression for a distal extension partial denture, but only a little studies were performed about displacement of soft tissue under distal extension partial denture base. The purpose of this study is to investigate the amount of vertical displacement of the soft tissue under distal extension partial denture base by different functional impression techniques. Impression techniques used were Z.O.P. Impression, Selective Tissue Placement Impression, Functional Relining Impression. Measurement of the vertical displacement of soft tissue were made with Depth Gauge and Measuring Platform. A Anatomic Impression was used as a control. The results were tested statistically using 3 way ANOVA and Scheffe test. The followings were the results obtained from this study. 1. The greatest amount of soft tissue displacement was observed in the center of the retromolar pad. 2. No significant differences were found between the crest of alveolar ridge and the buccal shelf area. 3. The greatest soft tissue displacement was observed in Functional Relining Impression using Iowa wax, and the least displacement was observed in Selective Tissue Placement Impression using murcaptan rubber base. 4. No significant differences were found between finger pressure and biting pressure in Z.O.P. Impression, but greater displacement was observed by biting pressure than finger pressure in Functional Reling Impression.

• 한국세라믹학회지
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• 제37권7호
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• pp.686-692
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• 2000

Tin-doped In2O3 (ITO) films were fabricated using a d.c. magnetron reactive sputteirng of a In-10 wt% Sn alloy target in an Ar and O2 gas mixture. To understand the behavior of the carrier mobility in ITO films with O2 partial pressure, the resistivity, carrier concentration and mobility, film density, and intrinsic stress in the films were measured with O2 partial pressure. It was found experimentally that the carrier mobility increased rapidly as the film density increased. In the ITO film with the density close to theoretical one, the mean free path was the same as the columnar diameter. This indicated that the mobility in ITO films was strongly influenced by the crystall size. However, in the case where the film density was smaller than a theoretical density, the mean free paths were also smaller the columnar diameter. It was analyzed that the electron scattering at pores and holes within the crystalline was the major obstacle for electron conduction in ITO films. The measurement of intrinsic stress in ITO films also made it clear that the density of ITO films was controlled by the bombardment of oxygen neutrals on the growing film.

• 대한토목학회논문집
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• 제14권3호
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• pp.679-688
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• 1994

본 연구에서는 UASB 반응조의 형상변화에 따른 입상슬러지의 물리 화학적 및 형태학적인 특성이 조사되었다. 또한 반응조내의 수소분압의 크기에 따른 반응조운전의 안정성이 조사되었다. 수소분압이 높게 유지된 수정개발된 UASB 반응조의 경우가 상대적으로 수소분압이 낮게 유지된 일반적인 UASB 반응조의 경우에 비해 입상슬러지의 침전성 및 미생물보유능이 더 우수하게 나타났다. 입상슬러지의 형성과 그 안정성에 수소분압이 큰 영향을 미치는 것으로 나타났다. 입상슬러지의 화학적 조성식은 일반적인 UASB 반응조와 수정개발된 UASB 반응조가 각각 $C_7H_{12}O_{4.6}N$과 $C_5H_9O_3N$으로, 일반적인 미생물의 경험식인 $C_5H_7O_2N$과는 상이하게 나타났다. 특히 수정개발된 UASB 반응조의 경우 입상슬러지내에 질소성분이 일반적인 혐기성 미생물보다 높게 나타나, 입상슬러지의 발생기작으로서 polypeptide계 체외폴리머의 존재가능성을 보여주고 있다. 전자현미경을 이용한 형태화적 특성조사결과, 일반적인 반응조의 경우와는 달리 수소분압이 높게 유지된 수정개발된 UASB 반응조의 경우 입상슬러지의 표면에서는 Methanobrevibactor arboriphilus와 같은 크기와 형태를 한 수소이용메탄균의 성장이 다발을 이루며 관찰되었는데, 이러한 현상은 입상슬러지의 형성 메커니즘을 뒷받침해주고 있다. 우수한 입상슬러지의 형성을 위해서는 상대적인 수소분압의 크기에 따른 효과적인 상분리가 이루어져, acetogens과 수소이용메탄균들간의 공생관계가 잘 유지되도록 해주어야 할 것으로 사료된다. 수정개발된 UASB 반응조가 일반적인 UASB 반응조에 비하여 수소이용메탄균의 성장에 더욱 효과적인 환경을 제공하는 것으로 판단되며, 입상슬러지의 경영성과 반응조 전체의 유기물질 제거효율 뿐만 아니라, 운전의 안정성 측면에서도 더 우수한 것으로 사료된다.