• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.4
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• pp.413-417
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• 2023

Gallium Oxide (Ga₂O₃) is preferred as a material for next generation power semiconductors. The Ga₂O₃ should solve the disadvantages of low thermal resistance characteristics and difficulty in forming an inversion layer through p-type ion implantation. However, Ga₂O₃ is difficult to inject p-type ions, so it is being studied in a heterojunction structure using p-type oxides, such as NiO, SnO, and Cu₂O. Research the lateral-type FET structure of NiO/Ga₂O₃ heterojunction under the Gate contact using the Sentaurus TCAD simulation. At this time, the VG-ID and VD-ID curves were identified by the thickness of the Epi-region (channel) and the doping concentration of NiO of 1×10¹⁷ to 1×10¹⁹ cm-3. The increase in Epi region thickness has a lower threshold voltage from -4.4 V to -9.3 V at I_D = 1×10^-8 mA/mm, as current does not flow only when the depletion of the PN junction extends to the Epi/Sub interface. As an increase of NiO doping concentration, increases the depletion area in Ga₂O₃ region and a high electric field distribution on PN junction, and thus the breakdown voltage increases from 512 V to 636 V at I_D =1×10^-3 A/mm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.2
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• pp.99-107
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• 1998

This dissertationhas confirmed the non-flam mability of cast mold transformer that is increasingly used lately. As a research progress, the investigation has been performed on the installation status and each line of the subway system which have the most mold transformer accidents, and the impediment status of the transformer for rectifier and the high-voltage distribution transformer per each manufacturer. Then, a high voltage mold of the actual mold transformer has been installed in the horiwntal heating furnace and the heat has been applied by the standard heating temperature curve of KSF 2257(Fireproof testing meth od of the construction structures: 1993). Accordingly, the combustibility of the mold transformer based on the test results has been found that 78 minutes has been required for the complete burning per the KSF 2257 combustion test curve and that, after stopping the heat application of the horizontal furnace after ignition, the flame progress has not been made but shown as the self-extinguishing characteristics when the flame progress has been checked. Thus, the non-flammability and self-extinguishability of the mold transformer have been confirmed. The result of this dissertation has indicated that the accident involving mold transformer has been progressed and expanded by the dielectric breakdown or void due to the crack in the mold rather than a fire accident caused by a short-circuit or an overload.r an overload.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.495-501
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• 2016

Mineral oil has been widely used as an insulating oil for electrical transformers for a long time, but the necessity of employing new insulation oil such as vegetable oil has been increased due to urgent needs for the biodegradability when it leaks and also for the thermal stability at a higher operation temperature. Although specific periods are required between the production and consumption, there are still short of the data to prove the insulation oils' storage stability depending upon various circumstances and their resources. Thus, this paper demonstrates the insulation oils' oxidation characteristics of both mineral and vegetable oils when each was exposed to different environments for 12 weeks. From this test, some properties including total acid number, water content and dielectric breakdown were changed under specific conditions and resources. Vegetable oils showed higher hydrophilicity and water saturation than those of mineral oils due to their molecular compositions. Under sunlight exposure condition, all insulation oils oxidized and changed their properties when exposing to the direct light, regardless of the resource used.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.17-18
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• 2011

Plasma in liquid phase has attracted great attention in the last few years by the wide domain of applications in material processing, decomposition of organic and inorganic chemical compounds and sterilization of water. The plasma in liquid is characterized by three main regions which interact each - other during the plasma operation: the liquid phase, which supply the plasma gas phase with various chemical compounds and ions, the plasma in the gas phase at atmospheric pressure and the interface between these two regions. The most complex region, but extremely interesting from the fundamental, chemical and physical processes which occur here, is the boundary between the liquid phase and the plasma gas phase. In our laboratory, plasma in liquid which behaves as a glow discharge type, is generated by using a bipolar pulsed power supply, with variable pulse width, in the range of 0.5~10 ${\mu}s$ and 10 to 30 kHz repetition rate. Plasma in water and other different solutions was characterized by electrical and optical measurements. Strong emissions of OH and H radicals dominate the optical spectra. Generally water with 500 ${\mu}S/cm$ conductivity has a breakdown voltage around 2 kV, depending on the pulse width and the repetition rate of the power supply. The characteristics of the plasma initiated in ultrapure water between pairs of different materials used for electrodes (W and Ta) were investigated by the time-resolved optical emission and the broad-band absorption spectroscopy. The deexcitation processes of the reactive species formed in the water plasma depend on the electrode material, but have been independent on the polarity of the applied voltage pulses. Recently, Coherent anti-Stokes Raman Spectroscopy method was employed to investigate the chemistry in the liquid phase and at the interface between the gas and the liquid phases of the solution plasma system. The use of the solution plasma allows rapid fabrication of the metal nanoparticles without being necessary the addition of different reducing agents, because plasma in the liquid phase provides a reaction field with a highly excited energy radicals. We successfully synthesized gold nanoparticles using a glow discharge in aqueous solution. Nanoparticles with an average size of less than 10 nm were obtained using chlorauric acid solutions as the metal source. Carbon/Pt hybrid nanostructures have been obtained by treating carbon balls, synthesized in a CVD chamber, with hexachloro- platinum acid in a solution plasma system. The solution plasma was successfully used to remove the template remained after the mesoporous silica synthesis. Surface functionalization of the carbon structures and the silica surface with different chemical groups and nanoparticles, was also performed by processing these materials in the liquid plasma.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.2
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• pp.83-90
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• 2023

The β-Ga₂O₃ has the most thermodynamically stable phase, a wide band gap of 4.8~4.9 eV and a high dielectric breakdown voltage of 8MV/cm. Due to such excellent electrical characteristics, this material as a power device material has been attracted much attention. Furthermore, the β-Ga₂O₃ has easy liquid phase growth method unlike materials such as SiC and GaN. However, since the grown pure β-Ga₂O₃ single crystal requires the intentionally controlled doping due to a low conductivity to be applied to a power device, the research on doping in β-Ga₂O₃ single crystal is definitely important. In this study, various source powders of un-doped, Sn 0.05 mol%, Sn 0.1 mol%, Sn 1.5 mol%, Sn 2 mol%, Sn 3 mol%-doped Ga₂O₃ were prepared by adding different mole ratios of SnO₂ powder to Ga₂O₃ powder, and β-Ga₂O₃ single crystals were grown by using an edge-defined Film-fed Growth (EFG) method. The crystal direction, crystal quality, optical, and electrical properties of the grown β-Ga₂O₃ single crystal were analyzed according to the Sn dopant content, and the property variation of β-Ga₂O₃ single crystal according to the Sn doping were extensively investigated.