• Vacuum Magazine
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• v.4 no.2
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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.

• Journal of Surface Science and Engineering
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• v.34 no.5
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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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• v.37 no.2
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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.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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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.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.117-138
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• 2006

Plasmas can be made by electrical discharge on earth. Most of the plasmas on earth have been generated in low pressure environments where the pressure is less than one millionth of the atmospheric pressure. However, there are many plasma applications which require high pressure plasmas. Therefore, scientists start research on plasma generation at high pressure to avoid use of expensive vacuum equipments. Large-volume inexpensive plasmas are needed in the areas of material processing, environmental protection and improvement, efficient energy source and applications, etc. We therefore developed new methods of plasma generations at high pressure and carried out research of applying these plasmas to high tech industries representing 21 century. These research fields will play pivotal roles in material, environmental and energy science and technology in future.

• Journal of Astronomy and Space Sciences
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• v.16 no.1
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• pp.41-52
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• 1999

Near-earth space is composed of plasmas which embed a number of plasma waves. Space plasmas consist of electrons and multi-ion that determine local wave propagation characteristics. In multi-ion plasmas, it is difficult to find out analytic solutions from the dispersion relation in general. In this work, we have developed a model with an arbitrary magnetic field and density as well as multi-ion plasmas. This model allows us to investigate how plasma waves behave when they propagate along realistic magnetic field lines, which are assumed by IGRF(International Geomagnetic Reference Field). The results are found to be useful for the analysis of the in situ observational data in space. For instance, if waves are assumed to propagate into the polar region, from the equatorial region, our model quantitatively show how polarization is altered along earth travel path.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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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.

• Journal of Surface Science and Engineering
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• v.29 no.6
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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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.

• Journal of Surface Science and Engineering
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• v.31 no.2
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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.