• Journal of the Microelectronics and Packaging Society
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• v.12 no.3 s.36
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• pp.227-233
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• 2005

Carbon nanotubes (CNT) which were grown, on the alumina substrate with a pair of comb-type Au electrodes, by plasma enhanced chemical vapor deposition have been investigated for $NO_2$ gas sensor. The electrical resistance of CNT film decreased with temperature, indicating a semiconductor type of CNT, and also the resistance of CNT sensor decreased with increasing $NO_2$ concentration. Upon exposure to $NO_2$ gas, the electrical resistance of CNT film sensor rapidly decreased within 3 minutes, and then showed a constant value after $20\~30$ minutes. It is found that the sensitivity of CNT sensor has been improved by air oxidation. The CNT sensor oxidized at $450^{\circ}C$ for 30 minutes showed higher sensitivity value than that without oxidation by $27\%$, even for a low 250 ppb $NO_2$ concentration at operating temperature of $200^{\circ}C$. But it needs a recovery time more than 20 minutes for reuse after detection of $NO_2$ gas.

• Journal of Korean Academy of Nursing
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• v.29 no.3
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• pp.711-720
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• 1999

The purpose of this study was to define the content of physiological knowledge needed for clinical nursing practices. Subjects of physiology were classified into 15 areas, and each areas was further classified into subareas, resulting in a total of 194 subareas. The degree of importance of each subarea was measured with a 4-point scale. The subjects of this study were 179 nurses of two university hospitals located in Seoul and Inchon. The results were as follows : 1. The areas of physiology necessary for clinical nursing practice as a basic knowledge in the order of importance were : blood, respiratory system and renal physiology, function of the immune system, body fluid and cardiovascular system, body temperature, endocrine physiology and gastrointestinal physiology However, the degree of importance for reproductive physiology, neuro-physiology, energy and metabolism, cell and cell membrane physiology, muscular physiology and special sense was relatively low. 2. The most important content of physiology for all clinical areas in nursing was blood physiology. However, the degree of importance for each physiology area was different depending on clinical areas. 3. Subareas of physiology as a basic knowledge for clinical practice and education in nursing were blood transfusion, blood type, function of red blood cell, white blood cell and platelet, characteristics and function of hemoglobin, composition and function of plasma protein, and mechanism of blood coagulation and anticoagulation. In conclusion, areas of physiology necessary for clinical nursing practice were blood, respiratory system and renal physiology, function of immune, body fluid and cardiovascular system, body temperature, endocrine physiology and gastrointestinal physiology. However, the degree of importance for each physiology area was different depending on clinical areas In nursing.

• Journal of the Korean Vacuum Society
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• v.16 no.4
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• pp.298-304
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• 2007

We have studied the effect of $N_2$ flow rate on the structural and optical properties of GaN nanorods grown on (111) Si substrates by radio-frequency plasma-assisted molecular-beam epitaxy. The hexagonal shape nanorods with lateral diameters from 80 to 190 nm with increasing $N_2$ flow rate from 1.1 to 2.0 sccm are obtained. However, the ratio of length (thickness) and compact region increases with increasing $N_2$ flow rate up to 1.7 sccm and then saturate. From the photoluminescence, free exciton transition is clearly observed for GaN nanorods with low $N_2$ flow rate. And the PL peak energies are blue-shifted with decreasing diameter of the GaN nanorods due to size effect. Temperature-dependent photoluminescence spectra for the nanorods with $N_2$ flow rate of 1.7 sccm show an abnormal behavior like "S-shape" with increasing temperature.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.81-83
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• 2000

Tin-doped indium oxide(ITO) thin films were deposited on polyethylene terephthalate(PET) at room temperature by oxygen ion beam assisted evaporator system and the effects of oxygen gas flow rate on the properties of room temperature ITO thin films were investigated. Plasma characteristics of the ion gun such as oxygen ions and atomic oxygen radicals as a function of oxygen flow rate were investigated using optical emission spectroscopy(OES). Faraday cup also used to measure oxygen ion density. The increase of oxygen flow rate to the ion gun generally increase the optical transmittance of the deposited ITO up to 6sccm of $O_2$ and the further increase of oxygen flow rate appears to saturate the optical transmittance. In the case of electrical property, the resistivity showed a minimum at 6 sccm of $O_2$ with the increase of oxygen flow rate. Therefore, the improved ITO properties at 6 sccm of $O_2$ appear to be more related to the incorporation of low energy oxygen radicals to deposited ITO film rather than the irradiation of high energy oxygen ions to the substrate. At an optimal deposition condition, ITO thin films deposited on PET substrates showed the resistivity of $6.6{\times}10^{-4}$ ${\Omega}$ cm and optical transmittance of above 90%.

• Journal of the Korean Vacuum Society
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• v.7 no.s1
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• pp.15-19
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• 1998

Structural and optical properties of $In_xGa_{1-X}N$ as well as $In_{0.1}Ga_{0.9}N$/GaN single quantum we11 (SQW) grown on sapphire (0001) substrate with an based GaN using rf-plasma assisted MBE have been investigated. The quality of the InXGal.,N fdm was improved as the growth temperature increased. In PL measurements at low temperatures, the band edge emission peaks of $In_xGa_{1-X}N$ was shifted to red region as an indium cell and substrate temperature increased. For $In_{0.1}Ga_{0.9}N$/GaN SQW, the optical emission energy has blue shift about 15meV in PL peak, due to the confined energy level in the well region. And, the FWHM of the $In_{0.1}Ga_{0.9}N$/GaN SQW was larger than that of the bulk Ino,la.9N films. The broadening of FWHM can be explained either as non-uniformity of Indium composition or the potential fluctuation in the well region. Photoconductivity (PC) decay measurement reveals that the optical transition lifetimes of the SQW measured gradually increased with temperatures.

• Clean Technology
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• v.18 no.1
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• pp.89-94
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• 2012

In this study, we investigated the activity of Pd and Pt supported on acidic Fe-ZSM5 supports for selective catalytic oxidation of ammonia ($NH_3$-SCO). Among the catalysts, Pt/Fe-ZSM5 catalyst exhibited superior $NH_3$-SCO activity to Pd/Fe-ZSM5 catalyst. We also tested Pt/Fe-ZSM5 catalysts with different Fe loading using ion-exchange method to prepare Fe-ZSM5 supports, which resulted in the increased catalytic performance with smaller Fe content: $NH_3$ was oxidized completely at low temperature ($250^{\circ}C$). The physicochemical properties of Fe-ZSM5 were investigated to figure out the relationship between the characteristics of the catalysts and the catalytic activity on $NH_3$-SCO by Inductively coupled plasma-atomic emissions spectrometer (ICP-AES), $N_2$ sorption, X-ray diffraction (XRD), temperature programmed desorption of $NH_3$ ($NH_3$-TPD) technique.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.6
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• pp.470-475
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• 2009

We deposited $Al_2O_3$ thin films on GaN by remote plasma atomic layer deposition (RPALD) technique, trimethylaluminum(TMA) and oxygen were used as precursors, at fixed process condition, the number of cycle were changed. Growth rate per cycle was $1.2\;{\AA}$/cycle. and Growth rate was in proportion to a number of cycle, the GaN MIS capacitors that $Al_2O_3$ thin film were deposited above 12 nm, have excellent electrical properties, a low electrical leakage current density(${\sim}10^{-10}\;A/cm^2$ at 1.5 MV), but below 12 nm, we can see the degradation of the leakage current density. After post deposition annealing, Dielectric constant was estimated by 1 MHz high-frequency C-V method, it was varied with the anealing temperature from 6.9 at no post anealed to 7.6 at $800^{\circ}C$, and we can see a improvement of the leakage current density and breakdown voltage by post deposition anealing below $700^{\circ}C$, but, after anealed at $800^{\circ}C$, we can see the degradation of the leakage current density and breakdown voltage.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.80-80
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• 2010

Graphene has attracted tremendous attention for the last a few years due to it fascinating electrical, mechanical, and chemical properties. Up to now, several methods have been developed exclusively to prepare graphene, which include micromechanical cleavage, polycrystalline Ni employing chemical vapor deposition technique, solvent thermal reaction, thermal desorption of Si from SiC substrates, chemical routes via graphite intercalation compounds or graphite oxide. In particular, polycrystalline Ni foil and conventional chemical vapor deposition system have been widely used for synthesis of large-area graphene. [1-3] In this study, synthesis of mono-layer graphene on a Ni foil, the mixing ratio of hydrocarbon ($CH_4$) gas to hydrogen gas, microwave power, and growth time were systemically optimized. It is possible to synthesize a graphene at relatively lower temperature ($500^{\circ}C$) than those (${\sim}1000^{\circ}C$) of previous results. Also, we could control the number of graphene according to the growth conditions. The structural features such as surface morphology, crystallinity and number of layer were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM), transmission electron microscopy (TEM) and resonant Raman spectroscopy with 514 nm excitation wavelength. We believe that our approach for the synthesis of mono-layer graphene may be potentially useful for the development of many electronic devices.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.1
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• pp.16-20
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• 2005

In order to improve electrical conductivity and mechanical properties of 8YSZ SOFC electrolyte material, we used Al₂O₃ as an additive and applied the spark plasma sintering (SPS) method. The sintered bodies were densified above 96 ％ of theoretical density at 1200℃ and possessed microstructures composed of homogeneous grains less than 1 ㎛ in size. The addition of Al₂O₃ improved fracture toughness and bending strength by inhibiting grain growth of 8YSZ and increased total ionic conductivity because grain interior conductivity appeared to remain constant and grain boundary conductivity increased. It was assumed that the dissolution of Al₂O₃ into 8YSZ which was inevitable problem at commercial sintering method was effectively prohibited by the SPS technique with a relatively low sintering temperature and the reaction between Al₂O₃ and SiO₂ present at grain boundary to produce the crystalline Al/sub 2-x/Si/sub l-y/O/sub 5/ phase, resulting in the increase of grain boundary conductivity.

• Journal of the Korean Chemical Society
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• v.50 no.1
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• pp.14-22
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• 2006

the basic model of chemical reactor using glow discharge, we used cathode discharge cell with vacant cavity in the middle. Currently glow discharge is widely studied as a radiation source or atomization device in atomic spectroscopy and remarkable technological achievements are made through the graft with other analysis devices such as microanalysis and steel analysis.1 Additionally, as the characteristics of basic glow discharge and radiation have been reviewed many times, those results could be used in this experiment.2-3 In 1993, an article regarding the treatment of poisonous gas in the air using low temperature plasma was published. According to this article, if DC Glow Discharge is used under continuous atmospheric flow, poisonous gases such as SO2 and NO can be removed.4 Based on those findings, we designed highly efficient reactor where stable air plasma is composed and all air flow pass the negative glow area passing through the tube. It was observed that the cathode tube type glow discharge developed in this study would be economical, easy to use and could be used as radiation source as well.