• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.163-166
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• 2002

We investigated structural and electrical properties of Metal-Oxide-Semiconductor(MOS) structure using Hafnium $oxide(HfO_{2})$ as high-k gate dielectric material. $HfO_{2}$ films are ultrathin gate dielectric material witch have a thickness less than 2.0nm， so it is spotlighted to be substituted $SiO_{2}$ as gate dielectric material. In this paper We have grown $HfO_{2}$ films with pt electrode on P-type Silicon substrate by RF magnetron sputtering system using $HfO_{2}$ target and oserved the property of semiconductor-oxide interface. Using pt electrode, it is necessary to be annealed at ${300^{\circ}C}$. This process is to increase an adhesion ratio between $HfO_{2}$ films with pt electrode. In film deposition process, the deposition time of $HfO_{2}$ films is an important parameter. Structura1 properties are invetigated by AES depth profile, and electrical properties by Capacitance-Voltage characteristic. Interface trap density are measured to observe the interface between $HfO_{2}$ with Si using High-frequency(1MHz) C-V and Quasi - static C-V characteristic.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.988-996
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• 1998

BN ceramics with 0.07wt% $V_{2}O_{5}$ and 0.03wt% CuO(BNC3V7) sintered at $900^{\circ}C$ where it is possible for these to be co-fired with Ag electrode. Dielectricconstant of 44.3, TCF of 22 ppm$/^{\circ}C$ and $Qxf_{o}$ value of 22,000 GHz can be obtained from BNC3V7, multilayer type band pass filters using tapped method and conventional method were designed for PCS (Personal Communication System) applications. Tapped method by adopting input/output-tapping scheme the chip filter stucture becomes simpler and needs fewer layers than that using the conventional input/output-coupling scheme. A multilayer type band pass filter fabricated by screen-printing with silver electrode after tape casting. The simulated characteristics of the fabricated filters sintered at $900^{\circ}C$ were compared with the designed ones. Even though the centered frequencies of tapped and conventional band pass chaip filters were measured to shift about 90MHz downward, the band pass characteristics of both filters were similar that of designed ones. The spuriousresonance characteristic of tapped pass chip filter was better than that of conventional chip filer.

• Nuclear Engineering and Technology
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• v.23 no.4
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• pp.420-425
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• 1991

The Rb charge exchange cell is constructed as the He- ion source of the SNU 1.5- MV Tandem Van do Graaff accelerator. The characteristic experiment is carried out in order to determine the optimum operational conditions of the cell. The $He^{+}$ ion beam with the energy of 1~10 keV, extracted from the duoplasmatron ion source, is passed through the Rb vapor to become He- ions by the two step charge exchange reaction, i.e., $He^{+}\;+\;Rb\;{\rightarrow}\;He^{\circ\ast}\;+\;Rb^{+}\;and\;He^{\circ\ast}\;+\;Rb\;{\rightarrow}\;He^{-}\;+\;Rb^{+}$. From the experimental results, it is found that the maximum fractional yield of $He^{-}$ ions is produced at He+ ion energy of 7 keV. The optimum temperatures of the oven and the canal are determined to be $370\;^{\circ}C{\;}and{\;}95^{\circ}C$ respectively. Under the optimum operational condition the maximum fractional yield of $He^{-}$ ions is $2.42\pm0.02%$ This charge exchange cell is proved to be an effective system for the production of He- ions.

• Journal of the Korean Ceramic Society
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• v.38 no.4
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• pp.380-387
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• 2001

140$0^{\circ}C$ 환원 분위기(질소-수소) 조건에서 열처리하여 반도성 SrTiO$_3$하소분말을 제조하였다. 하소분말을 이용하여 135$0^{\circ}C$에서 2시간동안 상압 소결하여 소결체를 제조하였으며, 이때 소결 분위기에 따른 소결체 입계의 전기적 특성을 고찰하였다. 이들 소결체는 전형적인 바리스터 특성을 나타내었으며, 특히 소결 분위기를 질소-수소로부터 공기로 변화시킴에 따라서 소결체의 문턱 전압, 입계 비저항 그리고 입계 전위 장벽은 430V/cm, 10MΩ.cm 그리고 2.0$\times$$10^{-3}$eV로부터 1000V/cm 이상, 240 MΩ.m 그리고 1.1eV로 변하였다.

• Corrosion Science and Technology
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• v.8 no.2
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• pp.89-92
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• 2009

Pure Ti as well as Ti-6Al-4V alloy exhibit excellent properties for dental implant applications. However, for a better biocompatibility it seems important to avoid in the composition the presence of V due to the toxic effects of V ion release. Thus Al and V free and composed of non-toxic element such as Nb, Zr alloys as biomaterials have been developed. Especially, Zr contains to same family in periodic table as Ti. The addition of Zr to Ti alloy has an excellent mechanical properties, good corrosion resistance, and biocompatibility. In this study, the electrochemical characteristics of Ti-Zr alloys for biomaterials have been investigated using by electrochemical methods. Methods: Ti-Zr(10, 20, 30 and 40 wt%) alloys were prepared by arc melting and homogenized for 24 hr at $1000^{\circ}C$ in argon atmosphere. Phase constitutions and microstructure of the specimens were characterized by XRD, OM and SEM. The corrosion properties of the specimens were examined through potentiodynamic test (potential range of -1500 ~ 2000 mV), potentiostatic test (const. potential of 300 mV) in artificial saliva solution by potentiostat (EG&G Co, PARSTAT 2273. USA).

• BMB Reports
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• v.32 no.4
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• pp.409-413
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• 1999

The cDNA encoding CMP-NeuAc:lactosylceramide ${\alpha}2$,3-sialyltransferase (GM3 synthase) was isolated from a human fetal brain cDNA library using sequence information obtained from amino acid sequences found in the conserved regions of the previously-cloned mouse GM3 synthase (mST3Gal V) and human sialyltransferases. The cDNA sequence included an open reading frame coding for 362 amino acids, and the primary structure of this enzyme predicted all the structural features characteristic of other sialyltransferases, including a type II membrane protein topology and both sialylmotifs. Comparative analysis of this cDNA with mST3Gal V showed 85% and 86% identity of the nucleotide and amino acid residues, respectively. The expression of this gene is highly restricted in both human fetal and adult tissues.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.4
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• pp.139-143
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• 2005

For application of carbon nano-tube (CNT) as a counter electrode materials of dye-sensitized solar cell (DSSC), the electrochemical behavior of CNT electrode was studied, employing cyclic-voltammetry (C-V) and impedance spectroscopy. Fabrication of CNT-paste and formation of CNT-counter electrode for characteristic measurement have been carried out using ball-milling and doctor blade process, respectively. Unit cell for measurements was assembled using Pt electrode, CNT electrode, and iodine-embedded electrolyte. Field emission-scanning electron microscopy (FE-SEM) was used for structural investigation of CNT powder and electrode. Sheet resistance of electrode was measured with 4-point probe method. Electrochemical properties of electrode, C-V and impedance spectrum, were studied, employing potentiogalvanostat (EG&G 273A) and lock in amplifier (EG&G 5210). As a results, the sheet resistance of CNT electrode is almost similar to that of F-doped SnO2 (FTO) coated glass substrate as approximately 10 ohm/sq. From C-V and impedance spectroscopy measurements, it was found that CNT electrode has high reaction rate and low interface reaction resistance between CNT surface and electrolyte. These results provides that CNT electrode were superior to that of conventional Pt electrode. Particularly, the reaction rate in the CNT electrode is about thrice high than Pt electrode. Therefore. CNT electrode is to be good candidate material for counter electrode in DSSC.

• Korean Journal of Materials Research
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• v.15 no.2
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• pp.139-142
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• 2005

[ $ZrO_2$ ] gate dielectric thin films were deposited by radio frequency (rf)-magnetron sputtering and its structure, surface morphology and electrical peoperties were studied. As the oxygen flow rate increases, the surface becomes smoother. The experimental results indicate that a high temperature annealing is desirable since it improves the electrical properties of the $ZrO_2$ gate dielectric thin films by decreasing the number of interfacial traps at the $ZrO_2/Si$ interface. The carrier transport mechanism is dominated by the thermionic emission.

• Journal of IKEEE
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• v.22 no.1
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• pp.180-184
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• 2018

Gallium oxide ($Ga_2O_3$) and silicon carbide (SiC) are the material with the wide band gap ($Ga_2O_3-4.8{\sim}4.9eV$, SiC-3.3 eV). These electronic properties allow high blocking voltage. In this work, we investigated the characteristic of $Ga_2O_3$ and 4H-SiC vertical depletion-mode metal-oxide-semiconductor field-effect transistors. We demonstrated that the blocking voltage and on-resistance of vertical DMOSFET is dependent with structure. The structure of $Ga_2O_3$ and 4H-SiC vertical DMOSFET was designed by using a 2-dimensional device simulation (ATLAS, Silvaco Inc.). As a result, 4H-SiC and $Ga_2O_3$ vertical DMOSFET have similar blocking voltage ($Ga_2O_3-1380V$, SiC-1420 V) and then when gate voltage is low, $Ga_2O_3-DMOSFET$ has lower on-resistance than 4H-SiC-DMOSFET, however, when gate voltage is high, 4H-SiC-DMOSFET has lower on-resistance than $Ga_2O_3-DMOSFET$. Therefore, we concluded that the material of power device should be considered by the gate voltage.

• Advances in nano research
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• v.12 no.1
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• pp.25-35
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• 2022

Within the framework of the density functional theory combined with the method of non-equilibrium Green's functions (DFT + NEGF), the features of electron transport in fullerene nanojunctions, which are «core-shell» nanoobjects made of a combination of fullerenes of different diameters C₂₀, C₈₀, C₁₈₀, placed between gold electrodes (in a nanogap), are studied. Their transmission spectra, the density of state, current-voltage characteristics and differential conductivity are determined. It was shown that in the energy range of -0.45-0.45 eV in the transmission spectrum of the "Au-C₁₈₀-Au" nanojunction appears a HOMO-LUMO gap with a width of 0.9 eV; when small-sized fullerenes C₂₀, C₈₀ are intercalation into the cavity C₁₈₀ the gap disappears, and a series of resonant structures are observed on their spectra. It has been established that distinct Coulomb steps appear on the current-voltage characteristics of the "Au-C₁₈₀-Au" nanojunction, but on the current-voltage characteristics "Au-C₈₀@C₁₈₀-Au", "Au-(C₂₀@C₈₀)@C₁₈₀-Au" these step structures are blurred due to a decrease in Coulomb energy. An increase in the number of Coulomb features on the dI/dV spectra of core-shell fullerene nanojunctions was revealed in comparison with nanojunctions based on fullerene C₆₀, which makes it possible to create high-speed single-electron devices on their basis. Models of single-electron transistors (SET) based on fullerene nanojunctions "Au-C₁₈₀-Au", "Au-C₈₀@C₁₈₀-Au" and "Au-(C₂₀@C₈₀)@C₁₈₀-Au" are considered. Their charge stability diagrams are analyzed and it is shown that SET based on C₈₀@C₁₈₀-, (C₂₀@C₈₀)@C₁₈₀- nanojunctions is output from the Coulomb blockade mode with the lowest drain-to-source voltage.