• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.123-123
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• 2015

Al doped ZnO(AZO) films as a transparent conductive oxide (TCO) electrode were deposited on glass, polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) at room temperature by a conventional rf-magneton sputtering (CMS) and a facing target sputtering (FTS) using Al2O3 and ZnO targets. In order to investigation of AZO properties, the structural, surface morphology, electrical, and optical characteristics of AZO films were respectively analyzed. The resistivities of AZO films using FTS system were $6.50{\times}10-4{\Omega}{\cdot}cm$ on glass, $7.0{\times}10-4{\Omega}{\cdot}cm$ on PEN, and $7.4{\times}10-4{\Omega}{\cdot}cm$ on PET substrates, while the values of AZO films using CMS system were $7.6{\times}10-4{\Omega}{\cdot}cm$ on glass, $1.20{\times}10-3{\Omega}{\cdot}cm$ on PEN, and $1.58{\times}10-3{\Omega}{\cdot}cm$ on PET substrates. The AZO-films deposited by FTS system showed uniform surface compared to those of the films by CMS system. We thought that the films deposited by FTS system had low stress due to bombardment of high energetic particles during CMS process, resulted in enhanced electrical conductivity and crystalline quality by highly c-axis preferred orientation and closely packed nano-crystalline of AZO films using FTS system.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.95.1-95.1
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• 2013

The RBSPICE (Radiation Belt Storm Probes Ion Composition Experiment) is one of five instrument suites onboard the twin Van Allan Probes (or Radiation Belt Storm Probes; RBSP), launched August 30, 2012 by NASA. One of science targets of RBSPICE instrument is to determine "how changes in that ring current affect the creation, acceleration, and loss of radiation belt particles?". For that purpose, it measures ions and electrons simultaneously. Ion's energy range is from ~20 keV to ~1 MeV and electron's energy channel is from ~35 keV to 1 MeV in order to provide supplementary information about the radiation belts. In this paper, we investigate a reliability of the electron flux measured from the RBSPICE by comparing with ECT (The Energetic Particle, Composition and Thermal Plasma Suite) data. We found there is a critical proton contamination problem in the electron channels of ~ 1MeV of RBSPICE observations during one moderate storm event of Sym H ~ -76 nT on March 1, 2013.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.457-460
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• 1997

The photoconductive gain mechanism in various types of hydrogenated amorphous silicon devices, such as p-i-n, n-i-n and n-i-p-i-n structures was investigated in connection with applications to radiation detection. We measured the photoconductive gain in two time scales: one for short pulses of visible light $(<1{\mu}sec)$ which simulate the transit of energetic charged particles, and the other for rather long pulses of light $(\sim1msec)$ which simulate x-ray exposure in medical imaging. We used two definitions of photoconductive gain: current gain and charge gain which is an integration of the current gain. We found typical charge gains of $3\sim9$ for short pulses and a few hundred for long pulses at a dark current density level of $10mA/cm^2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.1
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• pp.87-90
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• 2006

In case of preparation of ITO thin film for using top electrode of Top-emitting Organic Light Emitting Diodes(TOLEDs), the ITO thin film should be prepared at room temperature and low oxygen gas flow condition in order to reduced the damage of organic layer due to the bombardment of highly energetic particles such as negative oxygen ions which accrued from the plasma. In this study, the ITO thin film with high optical transmittance and low resistivity prepared as a function of oxygen gas (0 ${\~}$ 0.8 sccm) and Ar gas was fixed at 20 sccm by the Facing Targets Sputtering (FTS) method. The electrical and optical properties of ITO thin films were measured by Hall effect measurement, UV/VIS spectrometer, respectively In the results, we obtained the ITO thin film with lowest resistivity($3{\times}10^{-4} {\Omega}{\cdot} cm$) at oxygen gas flow 0.2 sccm and optical transmittance over $80\%$ at oxygen gas flow over 0.2 sccm.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.355-360
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• 1998

A small package of plasma instruments, Space Physics Sensor, will monitor the space environment and its effects on microelectronics in the low altitude region as it operates on board the KOMPSAT-1 from 1999 over the maximum of the solar cycle 23. The Space Physics Sensor (SPS) consists of two parts: the Ionospheric Measurement Sensor (IMS) and the High Energy Particle Detector (HEPD). IMS will make in situ Measurements of the thermal electron density and temperature, and is expected to provide a global map of the thermal electron characteristics and the variability according to the solar and geomagnetic activity in the high altitude ionosphere of the KOMPSAT-t orbit. HEPD will measure the fluxes of high energy protons and electrons, monitor the single event upsets caused by these energetic charged particles, and give the information of the total radiation dose received by the spacecraft. The continuous operation of these sensors, along with the ground measurements such as incoherent scatter radars, digital ionosondes and other spacecraft measurements, will enhance our understanding of this important region of practical use for the low earth orbit satellites.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.171-171
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• 2012

Neutral beam assisted chemical vapor deposition (NBa-CVD) process has been developed as a nove,l room temperature deposition process for the light-soaking free nano-crystalline silicon (nc-Si) thin films including intrinsic and n-type doped thin film. During formation of nc-Si thin films by the NBa-CVD process with silicon reflector at room temperature, the energetic particles enhance doping efficiency and crystalline phase in nc-Si thin films without additional heating at substrate. The effects of incident NB energy controlled by the reflector bias have been confirmed by Raman spectra analysis. Additionally, TEM images show uniform nc-Si grains which imbedded amorphous phase without incubation layer. The nc-Si films by the NBa-CVD are hardly degenerated by light soaking; the degradations of photoconductivity were just a few percents before and after light irradiation.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.94.2-94.2
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• 2011

Electron microbursts, energetic electron precipitation having duration less than 1 sec, have been thought to be generated by chorus wave and electron interactions. While the coincidence of chorus and microburst occurrence supports the wave-particle interaction theory, more crucial evidences have not been observed to explain the origin of microbursts. We propose the measurement of energy dispersion of microbursts could be an evidence supporting wave-particle theory. During chorus waves propagate along magnetic field, the resonance condition should be satisfied at different magnetic latitude for different energy electrons. If we observed electron microbursts at low altitude, the arrival time of different energy electrons should make unique dispersion structures. In order to observe such energy dispersion, we need a detector having fast time resolution and wide energy range. Our study is motivated from defining the time resolution and energy range of the detectors required to measure microburst energy dispersions. We performed test particles simulation to investigate how electrons interact with simple coherent waves like chorus waves. We compute a large number of electron's trajectories and successfully produce energy dispersion structures expected when microbursts are observed with 10 msec time resolution detectors at the altitude of 600 km. These results provide useful information in designing electron detectors for the future mission.

• Journal of Information Display
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• v.8 no.3
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• pp.5-10
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• 2007

Twin target sputtering (TTS) system with a configuration of vertically parallel facing Al targets and a substrate holder perpendicular to the Al target plane has been designed to realize a direct Al cathode sputtering on organic light emitting diodes (OLEDs). The TTS system has a linear twin target gun with ladder type magnet array for effective and uniform confinement of high density plasma. It is shown that OLEDs with Al cathode deposited by the TTS show a relatvely lower leakage current density $({\sim}1{\times}10^{-5}mA/cm^2)$ at reverse bias of -6V, compared to that ($1{\times}10^{-2}{\sim}10^{-3}$ $mA/cm^2$ at -6V) of OLEDs with Al cathodes grown by conventional DC magnetron sputtering. In addition, it was found that Al cathode films prepared by TTS were amorphous structure with nanocrystallines due to low substrate temperature. This demonstrates that there is no plasma damage caused by the bombardment of energetic particles. This indicates that the TTS system with ladder type magnet array could be useful plasma damage free deposition technique for direct Al cathode sputtering on OLEDs or flexible OLEDs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.74-75
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• 2007

We report on the characteristics of organic light-emitting diodes with Al cathode deposited by specially designed twin target sputter(TTS) system. It was found that the Al cathode films grown by TTS system were amorphous structure with nanocrystallines due to low substrate temperature during sputtering process. Effective confinement of high-density plasma between two Al targets lead to low temperature sputtering process on organic layer. Moreover, organic light-emitting diodes with Al cathode deposited by TTS system exhibited low leakage current density of $4{\times}10^{-6}\;mA/cm2$ at -6 V indicating plasma damage due to bombardment of energetic particles such as ions and $\gamma$-electrons was effectively restricted in the ITS system. Sputtering method using ITS system is expected to be applied in organic electronics and flexible displays due to its low temperature and plasma damage free deposition process.

• Journal of Powder Materials
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• v.26 no.3
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• pp.220-224
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• 2019

The aluminum (Al)/copper oxide (CuO) complex is known as the most promising material for thermite reactions, releasing a high heat and pressure through ignition or thermal heating. To improve the reaction rate and wettability for handling safety, nanosized primary particles are applied on Al/CuO composite for energetic materials in explosives or propellants. Herein, graphene oxide (GO) is adopted for the Al/CuO composites as the functional supporting materials, preventing a phase-separation between solvent and composites, leading to a significantly enhanced reactivity. The characterizations of Al/CuO decorated on GO(Al/CuO/GO) are performed through scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping analysis. Moreover, the functional bridging between Al/CuO and GO is suggested by identifying the chemical bonding with GO in X-ray photoelectron spectroscopy analysis. The reactivity of Al/CuO/GO composites is evaluated by comparing the maximum pressure and rate of the pressure increase of Al/CuO and Al/CuO/GO. The composites with a specific concentration of GO (10 wt%) demonstrate a well-dispersed mixture in hexane solution without phase separation.