• 진공이야기
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• 제4권2호
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• pp.4-9
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• 2017

Dusty plasmas consisting of electrons, ions, neutral gas molecules, and small solid-state 'dust' particles are ubiquitous. Examples include plasma processing, fusion plasmas, polar mesospheric clouds, Saturn's rings, comet tails, and protoplanetary disks. Since Voyager I and II discovered dusty plasmas in our solar system, dusty plasmas have been extensively studied from space & basic sciences to semiconductor & display industries. Here, a brief review on dusty plasma research is given and some remarkable results are introduced.

• 한국표면공학회지
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• 제34권5호
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• pp.367-377
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• 2001

Plasma is generated by electrical discharge. Most plasma generation has been carried out at low-pressure gas typically less than one millionth of atmospheric pressure. Plasmas are in general generated from impact ionization of neutral gas molecules by accelerated electrons. The energy gain of electrons accelerated in an electrical field is proportional to the mean free path. Electrons gain more energy at low-pressure gas and generate plasma easily by ionization of neutrals, because the mean free path is longer. For this reason conventional plasma generation is carried out at low pressures. However, many practical applications require plasmas at high-pressure. In order to avoid the requirement for vacuum pumps, researchers in Korea start to develop plasmas in high-pressure chambers where the pressure is 1 atmosphere or greater. Material processing, environmental protection/restoration and improved energy production efficiency using plasmas are only possible for inexpensive bulk plasmas. We thus generate plasmas by new methods and plan to set foundations for new plasma technologies for $21^{st}$ / century industries. This technological research will play a central role in material processing, environmental and energy production industries.

• Journal of Astronomy and Space Sciences
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• 제37권2호
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• pp.95-104
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• 2020

Properties of plasmas that constitute the plasma sheet in the near-Earth magnetotail vary according to the solar wind conditions and location in the tail. In this case study, we present multi-spacecraft observations by Cluster that show a transition of plasma sheet from cold, dense to hot, tenuous state. The transition was associated with the passage of a spatial boundary that separates the plasma sheet into two regions with cold, dense and hot, tenuous plasmas. Ion phase space distributions show that the cold, dense ions have a Kappa distribution while the hot, tenuous ions have a Maxwellian distribution, implying that they have different origins or are produced by different thermalization processes. The transition boundary separated the plasma sheet in the dawn-dusk direction, and slowly moved toward the dawn flank. The hot, tenuous plasmas filled the central region while the cold, dense plasmas filled the outer region. The hot, tenuous plasmas were moving toward the Earth, pushing the cold, dense plasmas toward the flank. Different types of dynamical processes can be generated in each region, which can affect the development of geomagnetic activities.

• 천문학회보
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• 제36권1호
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• pp.39.1-39.1
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• 2011

Coronal mass ejection (CME) plasmas have been observed in EUV and X-ray passbands as well as in white light. Mass of CME has been determined using polarized brightness observed by the Large Angle and Spectrometric Coronagraph Experiment (LASCO) on board Solar and Heliospheric Observatory (SOHO). Therefore, this mass obtained from the LASCO observation indicates the total CME mass. However, the mass of CME plasma in different temperatures can be determined in EUV and X-ray passbands using observations by SOHO/EIT, STEREO/EUVI, and Hinode/XRT. Prominence/CME plasmas have been observed as absorption or emission features in EUV and X-ray passbands. The absorption features provide a lower limit to cold mass. In addition, the emission features provide an upper limit to the mass of plasmas in temperature ranges of EUV and X-ray. We determine the mass constraints using the emission measure obtained by assuming the prominence/CME structures. This work will address the mass constraints of hot and cold plasmas in CMEs, comparing to total CME mass.

• 한국진공학회지
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• 제15권2호
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• pp.117-138
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• 2006

지표면에서 플라즈마는 전기방전에 의하여 만들어낸다. 그래서 대부분의 플라즈마 발생은 1백만분의 1기압보다 더 낮은 기압에서 발생하고 있었다. 그러나 많은 플라즈마 응용은 고기압에서 발생한 플라즈마를 요구하고 있다. 진공펌프와 같은 고가의 장비를 피하기 위하여 과학자들은 1기압이나 그이상의 압력에서 플라즈마를 발생하는 연구를 하기 시작했다. 많은 량의 제료 공정, 환경보호와 개선, 그리고 고효율 에너지 창출과 이용 등의 분야에 플라즈마를 사용할 때에는 오직 더 많은 량의 플라즈마를 더욱 값싸게 만들 때에만 가능한 것이다. 우리는 따라서 고기압에서 플라즈마를 만들어내는 새로운 방법을 개발하고 이러한 플라즈마가 21세기 산업에 적용될 수 있는 새로운 기반을 구축하는 연구를 수행하고 있다. 이러한 기술은 미래의 재료 공정이나, 환경 그리고 에너지 분야에 지대한 영향을 미칠 것으로 생각한다.

• Journal of Astronomy and Space Sciences
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• 제16권1호
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• pp.41-52
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• 1999

지구 주변에는 플라즈마로 가득 차 있고 그것을 매질로 하는 다양한 플라즈마 파동이 존재한다. 우주공간 플라즈마는 여러 종류의 이온과 전자로 구성되어 있고 특히 이온들은 파동의 전파에 많은 영향을 미친다. 다중 이온 플라즈마에서 파동분산 방정식의 해를 구하는 것은 상당히 복잡하다. 따라서, 임의의 자기장, 밀도를 고려하여 우주공간에서 다중 이온 플라즈마에서 파동의 분산관계를 쉽게 알 수 있는 계산모델을 개발하였다. 이 모델로부터 IGRF(International Geomagnetic Reference Field)에서 임의 지점을 지나는 자력선과 관측된 밀도 함수로부터 각 위도별로 가능한 파동들의 성질을 조사하여 위성의 초기 관측 자료 분석에 응용하였다. 예를 들어 POLAR 위성의 관측값 중에서 자기 적도 근처에서 발생되어 자력선을 따라 전파하는 특정한 범위의 주파수 경우 파동의 편극 상태가 변한 위치, 전파경로 등을 본 모델을 이용하여 예측할 수 있었다.

• 천문학회보
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• 제37권1호
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• pp.96.1-96.1
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• 2012

Various electromagnetic fluctuations are observed in the upstream of Earth's bow shock. Properties of plasmas are important in determining the development of the fluctuations. In this study we analyze the phase space distribution functions of plasmas measured by the Cluster spacecraft to understand how the fluctuations develop. Plasmas in the upstream of Earth's bow shock often consist of multiple components, especially when the fluctuations exist. In addition to the solar wind beams, backstreaming ion beams and diffuse ions are also often observed separately or simultaneously. The solar wind beams are not much perturbed even within the fluctuations. The diffuse ions are more than 10 times hotter than the solar wind beams and the backstreaming beams intermediate between them. The distribution functions of the diffuse and backstreaming ions are anisotropic to the magnetic field. Thus, they may be responsible for the fluctuations associated with temperature anisotropy. We will discuss about the thermalization processes and the relationship between the fluctuations and plasmas.

• 한국표면공학회지
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• 제29권6호
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• pp.816-823
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• 1996

Chlorine containing high density plasmas are widely used to etch various materials in the microelectronic device fabrication. In this study, the characteristics of inductively coupled $Cl_2(O_2/N_2$) plasmas and their effects on the formation of silicon etching have been investigated using a Langmuir probe, quadrupole mass spectrometry(QMS), X-ray photoelectron spectroscopy(XPS), and Scanning Electron Microscopy(SEM). The addition of oxygen for chlorine plasmas reduced ion current densities and chlorine radical densities compared to the nitrogen addition by the recombination of oxygen with chlorine. Also, when silicon is etched in $Cl_2/O_2$ plasmas, etch products recombined with oxygen such as $SiCl_xO_y$ emerged. However, when nitrogen is added to chlorine, etch products recombined with nitrogen or Si-N bondings on the etched silicon surface were not found. All the silicon etch characteristics were dependent on the plasma conditions such as ion density, radical density, etc. As a result sub micron vertical silicon trench etch profiles could be effectively formed using optimized etch conditions for $Cl_2/O_2\; and \;Cl_2/N_2$ gas combinations.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 영호남 합동 학술대회 및 춘계학술대회 논문집 센서 박막 기술교육
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• pp.15-19
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• 2006

A pulsed laser ablation deposition (PLAD) technique is an excellent method for the fabrication of amorphous carbon (a-C) films, because it can generate highly energetic carbon clusters on a substrate. This paper was focused on the understanding and analysis of the motion of C particles in laser ablation assisted by Ar plasmas. The simulation has carried out under the pressure P=50 mTorr of Ar plasmas. Two-dimensional hybrid model consisting of fluid and Monte-Carlo models was developed and three kinds of the ablated particles which are carbon atom (C), ion ($C^+$) and electron were considered in the calculation of particle method. The motions of energetic $C^+$ and C deposited upon the substrate were investigated and compared. The interactions between the ablated particles and Ar gas plasmas were discussed.

• 한국표면공학회지
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• 제31권2호
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• pp.117-126
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• 1998

In this study, the residue remaining on the silicon wafer during the oxide overetching using $C_4F_8/H_2$ helicon were plasmas and effects of various cleaning and annealing methods on the removal of the remaining residue were investigated. The addition of 30%$H_2$ to the C4F8 plasma increased the C/F ratio and the thickness of the residue on the etched silicon surface. Most of the residuse on the etched surfaces colud be removed by the oxygen plasmsa cleaning followed by thermal annealing over $450^{\circ}C$. Hydrogen-coataining residue formed on the silicon by 70%$C_4F_8/30%H_2$ helicon plasmas was more easily removed than hydrogen-free residue formed residue formed by $C_4F_8$ helicon wear plasmas. However, damage remaining on the silicon surface overetched using 70%$C_4F_8/30%H_2$ helicon plasmas was intensive and the degree of reocvery duing the post-annealing was lower.