• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.3
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• pp.145-152
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• 2003

Electrical gate and drain characteristics of double heterostructure InAlAs/InGaAs pseudomorphic HEMTs have been investigated under sub-bandgap photonic excitation ($hv). Drain $(V_{DS})-,{\;}gate($V_{DS})-$, and optical power($P_{opt}$)-dependent variation of the abnormal gate leakage current and associated physical mechanisms in the PHEMTs have been characterized. Peak gate voltage ($V_{GS,P}$) and the onset voltage for the impact ionization ($V_{GS.II}$) have been extracted and empirical model for their dependence on the $V_{DS}$ and $P_{opt} have been proposed. Anomalous gate and drain current, both under dark and under sub-bandgap photonic excitation, have been modeled as a parallel connection of high performance PHEMT with a poor satellite FET as a parasitic channel. Sub-bandgap photonic characterization, as a function of the optical power with $h\nu=0.799eV$, has been comparatively combined with those under dark condition for characterizing the bell-shaped negative humps in the gate current and subthreshold drain leakage under a large drain bias.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1385-1387
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• 1995

The Monte Carlo method for studying the steady-state behavior of electrons under the influence of a electric field is described. In this simulation used a Free Flight Time technique based on determination of the increase in kinetic energy between two collisions. The electron behavior in the cathode region of a corona discharge has been analysed using this method; spatial variations of the energy and excitation, ionization, and the multiplication of electrons were discussed.

• Electrical & Electronic Materials
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• v.10 no.5
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• pp.453-460
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• 1997

In order to investigate the electrical conduction properties of polyethylene thin film for power cable with manufacturing methods, the thickness of specimen was the 30, 100[${\mu}{\textrm}{m}$] of LDPE and 200[${\mu}{\textrm}{m}$] of XLPE were manufactured. The experimental condition for conduction properties was measured until the breakdown occurs at temperature ranges from 30 to 110[$^{\circ}C$] and the electric field from 1$\times$10$^3$to 5$\times$10$^{6}$ [V/cm]. As for increase of temperature, the current density of LDPE was increased with constant ratio in low field, but changes with exponential function in high electric field. The tunnel current of pre-breakdown region is shifted toward low field as much as thermal excitation energy. At low electric field, the XLPE showed dominant electrical conduction properties by thermal excitation, and transformation of the electron was resisted by the crystal at high electric field.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.35-36
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• 2000

The luminescence behaviors of Yttrium niobate and Bi doped Yttrium niobate were investigated under UV and low voltage electron excitations and interpreted with the first-principle calculations. In the UV excitation and emission spectra of $YNbO_4$ and $YNbO_4:Bi$, we were able to separate host contribution and Bi contribution and found that the shift in emission peak to longer wavelength is mainly due to Bi contribution. Using density functional theory, the cluster calculations were carried out for both $YNbO_4$ and $YNbO_4:Bi$. From the calculated density of states, we were also able to explain the charge transfer gap in the host and the effect of Bi in the excitation and emission spectra theoretically.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.2
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• pp.125-130
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• 2003

TiO$_2$ nanoparticles were prepared by photochemical synthesis in the dry toluene. The shape and size of the amorphous TiO$_2$ nanoparticles were investigated by transmission electron microscope. The particle size was varied by the contents of the titanium (IV) isopropoxide in dry toluene. Especially networked TiO$_2$ particles were formed from 40% titanium (IV) isopropoxide solution. The optical absorption spectra, photoluminescence, and PL excitation spectra of TiO$_2$ in dry toluene were obtained. The were shifted to the short wavelength as the contents of TiO$_2$ were increased. PL excitation had the peak at the wavelength regions is which the absorption increased steeply.

• Transactions on Electrical and Electronic Materials
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• v.18 no.3
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• pp.176-179
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• 2017

Non-vacuum processing technology was used to produce $Cs_3Sb$ photocathodes on substrates and fabricate in-situ panel devices. Electrical properties of these panel devices were characterized by measuring anode current and charge dose as functions of devices operation time. An excitation light source with a 475 nm wavelength was used for photocathodes. Results showed that emission properties of these photocathode emitters depended heavily on the vacuum level of these devices and that $Cs_3Sb$ flat emitters had the potential of operating for a long lifetime with stable electron emission characteristics via re-cesiation process in the panel device. These features make $Cs_3Sb$ photocathodes suitable as flat emitters in panel device applications.

• Bulletin of the Korean Chemical Society
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• v.17 no.7
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• pp.616-621
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• 1996

The transfer of excitation energy from solvent to solute in polystyrene films doped with 2-(2'-hydroxyphenyl)benzothiazole (HBT) which undergoes intramolecular proton transfer in excited electronic state has been studied by employing steady state and time-resolved fluorescence measurements. The degree of Forster overlap between donor and acceptor molecule in this system is estimated to be moderate. Energy transfer efficiency increases with solute concentration at low concentration range and levels off at high concentration. It is observed that the excimer form of polystyrene is largely involved in energy transfer process. Photostability of HBT in polystyrene to UV light is also investigated to get insight into the long wavelength absorption band of HBT which was observed upon electron radiation.

• Current Optics and Photonics
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• v.6 no.4
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• pp.413-419
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• 2022

An oxyfluoride glass ceramic containing Eu²⁺-doped nepheline and LaF₃ crystals was modified, with BaF₂ replacing LaF₃ up to 20 mole percent, and its luminescence change was monitored. With increasing BaF₂ content, the greenish yellow emission centered at 540 nm under 400-nm excitation decreased, and a new afterglow emission from the modified ceramic was observed after removal of the excitation light source. X-ray diffraction (XRD) and transmission electron microscopy with energy dispersive spectroscopy (TEM-EDS) were used to investigate the changes in the crystalline phases within the glass matrix. Time dependent emission intensity was monitored to observe the afterglow, and the possible mechanism for the afterglow due to BaF₂ addition was considered.

• Journal of Astronomy and Space Sciences
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• v.30 no.4
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• pp.247-253
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• 2013

It has long been known that the magnetospheric particles can precipitate into the atmosphere of the Earth. In this paper we examine such precipitation of energetic electrons using the data obtained from low-altitude polar orbiting satellite observations. We analyze the precipitating electron flux data for many periods selected from a total of 84 storm events identified for 2001-2012. The analysis includes the dependence of precipitation on the Kp index and the electron energy, for which we use three energies E1 > 30 keV, E2 > 100 keV, E3 > 300 keV. We find that the precipitation is best correlated with Kp after a time delay of < 3 hours. Most importantly, the correlation with Kp is notably tighter for lower energy than for higher energy in the sense that the lower energy precipitation flux increases more rapidly with Kp than does the higher energy precipitation flux. Based on this we suggest that the Kp index reflects excitation of a wave that is responsible for scattering of preferably lower energy electrons. The role of waves of other types should become increasingly important for higher energy, for which we suggest to rely on other indicators than Kp if one can identify such an indicator.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.310.1-310.1
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• 2013

We show the novel hot electron based-solar energy conversion using tandem structured Schottky diode with double Schottky barriers. In this report, we show the effect of the double Schottky barriers on solar cell performance by enhancing both of internal photoemission and band-to-band excitation. The tandem structured Au/Si diode capped with TiO2 layer as second semiconductor exhibited improved ability for light harvesting. The proposed mechanisms consist of multiple reflections of hot electrons and additional pathway of solar energy conversion due to presence of multiple interfaces between thin gold film and semiconductors. Short-circuit photocurrent measured on the tandem structured Au/Si diodes under illumination of AM1.5 increased by approximately 70% from 3.1% to 5.3% and overall incident photon to electron conversion efficiency (IPCE) was enhanced in visible light, revealing that the concept of the double Schottky barriers have significant potential as novel strategy for light harvesting.