• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.198.2-198.2
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• 2016

Reactive oxygen and nitrogen species (RONS) can be generated by using non-thermal atmospheric pressure plasma jet which have profound biomedical applications [1, 2]. In this work, reactive oxygen species like hydroxyl radical (OH) are generated by using non-thermal direct plasma jet above water surface using Ar gas and their properties have been studied using ultraviolet absorption spectroscopy. OH radicals are found to be generated simultaneously with the discharge current with concentration of $2.7{\times}1015/cm3$ at 7mm above water surface while their persistence time have been measured to be $2.8{\mu}S$. In addition, it has been shown that plasma initiated ultraviolets play a major role to generate RONS inside water. Further works are going on to measure the temporal behavior of OH and $O2^*-$.

• Journal of the Korean Ceramic Society
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• v.30 no.2
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• pp.148-156
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• 1993

TiN films were deposited onto high speed steel (SKH9) by plasma assisted chemical vapor deposition (PACVD) using a TiCl4/N2/H2/Ar gas mixture at around 50$0^{\circ}C$. The effects of the deposition temperature, R.F. power and TiCl4 concentration on the deposition of TiN and the microhardness of TiN film were investigated. The crystallinity and the microhardness of TiN films were improved with increase of the deposition temperature. Optimum deposition temperature in this study was 50$0^{\circ}C$, because a softening or phase transformation of the substrate occurred over 50$0^{\circ}C$. A large increase of the film growth rate with a strong(200) preferred orientation was obtained by increasing R.F. power. Much chlorine content of about 10at.% was found in the deposited films and resulted in relatively low average microhardness of about 1, 500Kgf/$\textrm{mm}^2$ compared with the theoretical value(~2, 000Kgf/$\textrm{mm}^2$).

• Journal of the Korean Ceramic Society
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• v.26 no.4
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• pp.539-549
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• 1989

Polycrystalline TiO2 thin films were deposited on Si and Al2O3 substrates by CVD method. Ethyl titanate, Ti(OC2H5)4, was used as a source material for Ti and O, and Ar was used for carrier gas. In the surface chemical reaction controlled deposition condition, the apparent activation energy of 6.74 Kcal/mole was obtained, and the atomic adsorption on substrate surface was proved to be governed by Rideal-Elley mechanism. In the mass transfer controlled deposition condition, the deposition rate was in a good agreement with the result which was calculated by the simple boundary layer theory. It was also observed that TiO2 thin films show different surface morphology according to the different deposition mechanism, which was fixed by deposition conditions. This phenomenon could be well explained by the surface perturbation theory.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.446-450
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• 2013

TRISO coated particles with a ZrC barrier layer were fabricated by a fluidized-bed chemical vapor deposition (FBCVD) method for a use in a very high temperature gas-cooled reactor (VHTR). The ZrC layer was deposited by the reaction between $ZrCl_4$ and $CH_4$ gases at $1500^{\circ}C$ in an $Ar+H_2$ mixture gas. The amount of free carbon codeposited with in ZrC was changed by controlling the dilution gas ratio. Near-stoichiometric ZrC phase was also deposited when an impeller was employed to a $ZrCl_4$ vaporizer which effectively inhibited the agglomeration of $ZrCl_4$ powders during the deposition process. A near-stoichiometric ZrC coating layer had smooth surface while ZrC containing the free carbon had rough surface with tumulose structure. Surface roughness of ZrC increased further as the amount of free carbon increased.

• Korean Journal of Materials Research
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• v.7 no.9
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• pp.811-823
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• 1997

차세대 반도체 배선분야에서, Cu박막은 현재의 AI을 대체할 물질로서 대두되고 있으며 CVD에 의한 선택적 증착은 Cu의 patterning과 관련하여 상당한 관심을 일으키고 있다. 본 연구에서는 (hfac)Cu(VTMS)의 유기원료를 사용하여, CVD공정변수, 운반기체, 표면 처리 공정에 따른 SiO$_{2}$, TiN, AI기판에 대한 선택성을조사하였다. 선택성은 저온(15$0^{\circ}C$), 저합(0.3Torr)에서 향상될 수 있었으며, 특히, HMDS in-situ-predosing공정에 의해 더욱 향상될 수 있었다. 모든 경우에 대해, H$_{2}$운반기체가 Ar 보다 짧은 incubation time과 높은 증착 속도가 얻어졌으며, Cu입자들의 크기가 작고 연결상태가 보다 양호하였다. 이는 H$_{2}$경우에 기판표면에 원료가 흡착되어 핵을 형성시키는 위치 (-OH)가 보다 많이 제공되기 때문으로 여겨진다. 이러한 미세구조의 차이는 H$_{2}$경우에 보다 낮은 비저항을 얻게 했다. HMDS in-situ predosing공정에 의한 Cu박막내 불순물 차이는 없었으며 뚜렷한 비저항의 차이도 나타나지 않았다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.482-482
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• 2012

대기압 플라즈마 소스는 미생물을 살균하는 효과를 가지고 있으나 그 메커니즘에 대해서는 여전히 많은 연구가 필요한 실정이다. 우리는 본 연구에서 메커니즘 규명을 위한 시작단계로 플라즈마에 대한 미생물의 반응을 생물학적 및 물리적 분석을 통해 보고자 하였다. 연구에 사용한 미생물은 yeast인 Saccharomyces cerevisiae 이며 Ar Gas 플라즈마를 사용하였다. Yeast에 일정한 시간 동안 플라즈마를 조사한 후 세포의 생존, 모양 변화 관찰 및 DNA에 대한 영향이 분석되었고 r-FIB 장비를 이용하여 세포표면의 이차전자 방출계수를 측정하였다. 플라즈마 조사 시간에 따라 Yeast active cell의 수가 감소하며, water에 넣고 조사할때에는 YPD media에 넣고 조사한 것에 비해 급격히 감소함을 볼 수 있다. 셀의 모양 관찰 결과도 water에 넣고 조사할 때, YPD media보다 더 찌그러듬을 볼 수 있다. 플라즈마 조사량에 따라서 Water의 PH 값은 YPD에 비해 급격히 낮아짐을 보인다. pH의 값을 달리하고 SNP와 H2O2가 첨가된 water에 Yeast를 배양시킬 때, pH의 값이 낮아질수록 yeast의 생존도 감소함을 볼 수 있다. 그리고 DNA gel electrophoresis를 통해 플라즈마 처리를 하게되면 Yeast의 DNA 양이 감소하는 것을 관찰할 수 있다. 또한 플라즈마 처리를 3분 하였을 때의 Yeast 세포막으로부터 방출되는 이차전자방출계수는 다른 처리시간에 대한 값에 비하여 확연히 증가하는 것을 볼 수 있다. 이들 사실로부터 플라즈마의 효과로 인해 외부의 전자를 흡수 및 차단할 수 있는 기능을 갖고 있는 Yeast 세포막의 구조가 변형되어 손상되었음을 의미한다.

• Journal of the Korean Vacuum Society
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• v.12 no.2
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• pp.86-92
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• 2003

The pumping characteristics of a commercial UHV cryopump with a G-M refrigerator for various gases were investigated. The pumping speeds as a function of pumped amount of $H_2,\; D_2,\; He,\; Ar,\; N_2$, CO and the pumping capacity of $N_2$ were measured and the trend was theoretically analyzed. The spectrum change of the residual gas was also investigated during cyropump operation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.78-79
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• 2008

In this paper, poly 3C-SiC thin films were grown on $SiO_2$/Si by atmospheric pressure chemical vapor deposition (APCVD) using HMDS, $H_2$, and Ar gas at $1100^{\circ}C$ for 30 min, respectively. And then, palladium films were deposited on poly 3C-SiC by RF magnetron sputter. Thickness, uniformity, and quality of these samples were performed by SEM. Crystallinity and preferred orientationsof palladium were analyzed by XRD. And Pd/poly 3C-SiC schottky diodes were fabricated and characterized by current-voltage measurements. Its electric current density Js and barrier height voltage were measured as $2\times10^{-3}$ A/$cm^2$, 0.58 eV, respectively. And these devices operated about $350^{\circ}C$. From results, Pd/poly 3C-SiC devices are promising for high temperature hydrogen sensor and applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.2
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• pp.98-102
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• 2010

This paper describes that single crystalline 3C-SiC (cubic silicon carbide) thin films have been deposited on carbonized Si(100) substrates using hexamethyldisilane (HMDS, $Si_2(CH_3){_6}$) as a safe organosilane single precursor and a nonflammable mixture of Ar and $H_2$ gas as the carrier gas by APCVD at $1280^{\circ}C$. The deposition was performed under various conditions to determine the optimized growth condition. The crystallinity of the 3C-SiC thin film was analyzed by XRD (X-ray diffraction). The surface morphology was also observed by AFM (atomic force microscopy) and voids between SiC and Si interfaces were measured by SEM (scanning electron microscopy). Finally, residual strain and hall mobility was investigated by surface profiler and hall measurement, respectively. From these results, the single crystalline 3C-SiC film had a good crystal quality without defects due to viods, a low residual stress, a very low roughness.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.91-91
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• 2009

In the past decade, Pd based thin films have been studied far hydrogen gas sensors due to their high possibility for energy industry and environmental applications. In this work, we report a navel method to fabricate highly sensitive hydrogen gas sensors based on PdO thin films. The films were deposited on Si substrates in Ar and $O_2$ ambient using reactive sputtering system. A semiconductor process has been utilized to fabricate PdO films with t=40nm. We observed the resistance changes of the PdO films with various $H_2$ concentrations. It was found that the electrical properties of the thin films depend on the composition of oxygen. The sensitivity is defined as $S\;=\;(R_0-R)/R{\times}100%$, where R and $R_0$ are the resistances in the presence of exposing the hydrogen gas and air, respectively. The sensitivity of the thin films was found to be as high as about 95%. After exposing to hydrogen gas, we discovered that the nano-sized cracks formed on the surface of the PdO thin films. The nano-cracks formed in deoxidized PdO thin films were known by playing a key role to reduce more than 4 times the response time of absorption. Our results illustrate that the deoxidized PdO thin films can be used as hydrogen sensors.