• The Korean Journal of Ceramics
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• v.3 no.1
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• pp.13-17
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• 1997

It is identified that the diamond films grown o bias-treated (100) silicon showed different surface morphologies and film textures according to the initial applied dc bias voltage at the same growth condition. The highly oriented diamond film (HODF) was successfully grown on -200 V bias-treated silicon substrate in which the heteroepitaxial relation of $(100)_{dimond}//(100)_{si}\; and\; [110]_{diamond}//[110]_{si}$ was identified. On the contrary, the heteroepitaxial relation was considerably disturbed in the samples bias-voltage was a key factor in growing the highly oriented diamond film on (100) silicon substrate. Considering the experimental results, we proposed a new model about heteroepitaxial diamond growth on silicon, in which 9 diamond unit cell are matched with 4 silicon cells and the bond covalency of both atoms is satisfied via the intermediate layer at the interface as well.

• Journal of the Korean Vacuum Society
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• v.2 no.4
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• pp.501-506
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• 1993

The spatial potential distribution of electron cyclotron resonance plasma is measured as a function of tehsubstrate DC bias by Langmuir probe method. It is observed that the substrate DC bias changes the slope of the plasma potential near the subsrate, resulting in changes in flux and energy of the impinging ions across plasma $_strate boundary along themagnetric field. The effect of the substrate DC bias on the low-temperature silicon homoepitaxy (below $560^{\circ}C$) is examine dby in situ reflection high energy electron diffraction (RHEED), cross-section transmission electron microscopy (XTEM),plan-view TEM and high resolution transmision electron microscopy(HRTEM). While the polycrystalline silicon layers are grow withnegative substrate biases, the single crystaline silicon layers are grown with negative substrate biases, the singel crystalline silicon layers are grown with positive substrate biases. As the substrate bias changes form negative to positive values, the growth rate decreases. It is concluded that the control of the ion energy during plasma deposition is very important in silicon epitaxy at low temperatures below $560^{\circ}C$ by UHV-ECRCVD.VD.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.384-393
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• 2013

In this paper, a design of planar microwave bias-tee using lumped elements was presented. The bias-tee is composed of 2 blocks; DC block and RF choke. For this design of the bias-tee, a wideband capacitor was used for DC block. For a RF choke, a series connection of inductors which have different SRFs is used for a RF choke. In the RF choke, a series connection of resistor and capacitor was added in shunt to eliminate a loss from a series resonance. The designed bias-tee was implemented by using 1608 SMT chip components. The fabricated bias-tee was measured using Anritsu 3680K fixture which enables to remove an effect of a connector. The fabricated bias-tee presented -15 dB of return loss and -1.5 dB insertion loss at 10 MHz~18 GHz.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.176-187
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• 2015

DC bias will cause abnormal vibration of transformers. Aiming at such a problem, transformer vibration affected by DC bias has been studied combined with transformer core and winding vibration mechanism use multi-physical field simulation software COMSOL in this paper. Furthermore the coupling model of electromagnetic-structural force field has been established, and the variation pattern of inner flux density, distribution of mechanical stress, tension and displacement were analyzed based on the coupling model. Finally, an experiment platform has been built up which was employed to verify the correctness of model.

• Transactions on Electrical and Electronic Materials
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• v.12 no.5
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• pp.197-199
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• 2011

In this paper, the bottom-gate thin-film transistors (TFTs) were fabricated with an amorphous/microcrystalline Si double layer (DL) as an active layer and the variations of the electrical characteristics were investigated according to the DC bias stresses. Since the fabrication process of DL TFTs was identical to that of the conventional amorphous Si (a-Si) TFTs, it creates no additional manufacturing cost. Moreover, the amorphous/microcrystalline Si DL could possibly improve stability and mass production efficiency. Although the field effect mobility of the typical DL TFTs is similar to that of a-Si TFTs, the DL TFTs had a higher reliability with respect to the direct current (DC) bias stresses.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.8
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• pp.713-719
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• 2002

In this study, the vertically well-aligned CNTs were synthesized by DC bias-assisted inductively coupled plasma hot-filament chemical vapor deposition (ICPHFCVD) using radio-frequence plasma of high density and that CNTs were vertically grown on Ni(300 )/Cr(200 )-deposited glass substrates at 58$0^{\circ}C$. This system(ICPHFCVD) added to tungsten filament in order to get thermal decompound and DC bias in order to vertically grow to general Inductively Coupled Plasma CVD. The grown CNTs by ICPHFCVD were developed to higher graphitization and fewer field emission properties than those by general ICPCVD. In this system, DC bias was effect of vortical alignment to growing CNTs. The measured turn-on fields of field emission property by general ICPCVD and DC bias-assisted ICPHFCVD were 5 V/${\mu}{\textrm}{m}$ and 3 V/${\mu}{\textrm}{m}$, respectively.

• Journal of Magnetics
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• v.17 no.4
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• pp.245-250
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• 2012

Ferromagnetic resonance and X-ray specular reflectivity measurements were performed on $Ni_{81}Fe_{19}/Ir_{20}Mn_{80}/Co_{90}Fe_{10}$ exchange bias trilayers, which were grown using the pulsed-DC magnetron sputtering technique on Si(100)/$SiO_2$(1000 nm) substrates, to investigate the evolution of the interface roughness and exchange bias and their dependence on the NiFe layer thickness. The interface roughness values of the samples decrease with increasing NiFe thickness. The in-plane ferromagnetic resonance measurements indicate that the exchange bias field and the peak-to-peak line widths of the resonance curves are inversely proportional to the NiFe thickness. Furthermore, both the exchange bias field and the interface roughness show almost the same dependence on the NiFe layer thickness. The out-of plane angular dependent measurements indicate that the exchange bias arises predominantly from a variation of exchange anisotropy due to changes in interfacial structure. The correlation between the exchange bias and the interface roughness is discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.9
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• pp.687-692
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• 1998

Silicon doped $Al_{0.32}Ga_{0.68}As$ were growth by molecular beam epitaxy. Electroreflectance(ER) spectra of the $E_1$ transition of Schottky barrier Au/n-$Al_{0.32}Ga_{0.68}As$ have been measured at various modulation voltage($V_{ac}$) and dc bias voltage($V_{bias}$). from the $E_1$peak, band gap energy of the $Al_{0.32}Ga_{0.68}As$ is 1.883 eV which corresponds to an Al composition of 32%. As modulation voltage($V_{bias}$) is changed, a line shape at the $E_1$transition does not change, but its amplitude varies linearly. The amplitude of $E_1$signal decrease with increasing the forward dc bias voltage($V_{bias}$), but the line shape does not change. It suggests that the low field theory rather than Franz-Keldysh oscillation is Required to interpret spectra. Also, spectra at the $E_1$transition were broadened with increasing the reverse dc bias voltage($V_{bias}$) which suggests the presence of Field-induced broadening.

• Journal of the Korean Magnetics Society
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• v.23 no.3
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• pp.94-97
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• 2013

Orthogonal fluxgate sensor was fabricated with cylinder-shaped NiZn ferrite core, Cu wire through the core and pickup coil wound on the core, and the bias current effect on the output sensitivity of it was investigated. The output ($$\sim_\sim$$ sensitivity) of the sensor was largely dependent on the operation frequency, and the tendency of sensor output was similar to that of the impedance of pickup coil. The maximum output was obtained by adding the DC bias current of which value was over 50% of the excitation current. The output was saturated when the DC bias current was larger than 50% of the excitation current.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.781-789
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• 2018

This paper proposes a new approach utilizing empirical mode decomposition (EMD) reconstruction to process vibration signals of a transformer under DC bias caused by high voltage direction transmission (HVDC), which is the potential cause of additional vibration and noise from transformer. Firstly, the Calculation Method is presented and a 3D model of transformer is simulated to analyze transformer deformation characteristic and the result indicate the main vibration is produced along axial direction of three core limbs. Vibration test system has been built and test points on the core and shell of transformer have been measured. Then, the signal reconstruction method for transformer vibration based on EMD is proposed. Through the EMD decomposition, the corrupted noise can be selectively reconstructed by the certain frequency IMFs and better vibration signals of transformer have been obtained. After EMD reconstruction, the vibrations are compared between transformer in normal work and with DC bias. When DC bias occurs, odd harmonics, vibration of core and shell, behave as a nonlinear increase and the even harmonics keep unchanged with DC current. Experiment results are provided to collaborate our theoretical analysis and to illustrate the effectiveness of the proposed EMD method.