• Fire Science and Engineering
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• v.20 no.3 s.63
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• pp.35-41
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• 2006

In this study, we presented the problems in the insulation cover of 22.9kV transformer bushing through investigating actual conditions. After thermal stress applied to the insulation cover, deterioration patterns, thermogravimetric and infrared characteristics were analyzed, and the results were applied to the cause analysis of accidents and judgement of safety. The insulation covers are used to protect exposed terminals of transformer, but they had improper size and length. Therefore, they could not show efficient insulation function. In case that thermal stress of $150^{\circ}C$ was applied to the insulation covers, plastic insulation covers(A, B, D, E) damaged severely, whereas rubber insulation cover(C) showed normal shapes. In the result of thermogravimetric analysis, the thermal gravity of plastic covers(A) decreased about 33.3% at $307.8^{\circ}C\;to\;405.9^{\circ}C$. and he thermal gravity of rubber covers (C) decreased about 53.7% at $258.8^{\circ}C\;to\;32.9^{\circ}C$. In the result of FT-IR analysis, plastic covers showed peaks characteristic of $CH_2,\;CH_3$, C=O and C=C bonds, whereas rubber covers showed peaks characteristic of OH, $CH_2,\;CH_3$, C=O, C=N and C=C bonds.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1352-1354
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• 1998

$LiNbO_3$ transistor showed relatively stable characteristic, low interface trap density, and large remanent polarization. This paper reports ferroelectric $LiNbO_3$ thin films grown directly on p-type Si(100) substrates by 13.56 MHz rf magnetron sputtering system for FRAM applications. To take advantage of low temperature requirement for growing films, we deposited $LiNbO_3$ films lower than $300 ^{\circ}C$. RTA(Rapid Thermal Anneal) treatment was performed for as-deposited films in an oxygen atmosphere at $600^{\circ}C$ for 60 sec. We learned from X-ray diffraction that the RTA annealed films were changed from amorphous to poly-crystalline $LiNbO_3$ which exhibited (012), (015), and (022) orientations. The I-V characteristics of $LiNbO_3$ films before and after anneal treatment showed that RTA improved the leakage current of films. The leakage current density of films decreased from $10^{-5}$ to $10^{-7} A/cm^2$ at room temperature measurement. Breakdown electric field of the films exhibited higher than 500 kV/cm. The C-V curves showed the clockwise hysteresis represents ferroelectric switching characteristics. From C-V curves, we calculated dielectric constant of thin film $LiNbO_3$ as 27.5 which is close to that of bulk value.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.5
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• pp.497-503
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• 2015

It is essential to acquire an accurate and simple technique for extracting the interface trap density ($D_{it}$) in order to characterize the normally-off gate-recessed AlGaN/GaN hetero field-effect transistors (HFETs) because they can undergo interface trap generation induced by the etch damage in each interfacial layer provoking the degradation of device performance as well as serious instability. Here, the frequency-dependent capacitance-voltage (C-V) method (FDCM) is proposed as a simple and fast technique for extracting $D_{it}$ and demonstrated in normally-off gate-recessed AlGaN/GaN HFETs. The FDCM is found to be not only simpler than the conductance method along with the same precision, but also much useful for a simple C-V model for AlGaN/GaN HFETs because it identifies frequency-independent and bias-dependent capacitance components.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.10
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• pp.1-8
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• 2009

In this paper, a temperature variation-insensitive power-up detector for use in analog and digital integrated systems has been proposed. To provide temperature-insensitive characteristic, nMOS and pMOS voltage dividers in the proposed power-up detector are made to have zero temperature coefficient by exploiting the fact that the effective gate-source voltage of a MOS transistor can result in mutual compensation of mobility and threshold voltage for temperature independency. Comparison results using a 68-nm CMOS process indicate that the proposed power-up detector achieves as small as 4 mV voltage variation at 1.0 V power-up voltage over a temperature range of $-30^{\circ}C$ to $90^{\circ}C$, resulting in 92.6% reduction on power-up voltage variations over conventional power-up detectors.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.1
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• pp.51-56
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• 2012

In the present study, we investigated the effect of mechanical alloying (MA) on the formation of amorphous VCo system through solid state reaction during ball milling. Two types of powder samples, ${\sigma}$-VCo intermetallic compound and $V_{50}Co_{50}$ powder mixture, were applied as a starting materials. With increasing milling time, a structural characteristics into the amorphous state is distinctly observed from the structural factor and radial distribution by X-ray diffraction. Amorphization has been observed in all two types of samples after the milling for 120 hrs. DSC spectrum of $V_{50}Co_{50}$ powder sample milled for 60 hrs indicates a sharp exothermic peak from the crystallization at $600^{\circ}C$. The structure factor, S(Q) and radial distribution function, RDF(r), observed by X-ray diffraction gradually change into a structure characteristic of an amorphous state with increasing MA time.

• Journal of Satellite, Information and Communications
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• v.10 no.2
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• pp.75-79
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• 2015

In this study, we investigated the electro-optical (EO) characteristic of fringe-field switching (FFS) mode cell by the ion beam alignment method on the a-C:H thin film. The suitable inorganic thin films for FFS cell and the aligning capabilities of nematic liquid crystal (NLC) using the new alignment material of a-C:H thin film were studied. An excellent voltage-transmittance (V-T) and response time curve of the ion beam aligned FFS-LCD was observed with oblique ion beam exposure on the a-C:H thin films. Also, the V-T hysteresis characteristics of the ion beam-aligned FFS-LCD with IB exposure on the a-C:H thin films is almost the same as that of the rubbing-aligned FFS cell on a polyimide surface.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.4
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• pp.23-28
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• 2004

In this paper, the properties of Mo as PMOS gate electrodes were studied. The work-function of Mo extracted from C-V characteristic curves was appropriate for PMOS. To identify the electrical and chemical stability of Mo metal gate, the changes of work-function and EOT(Effective Oxide Thickness) values were investigated after 600, 700, 800 and 90$0^{\circ}C$ RTA(Rapid Thermal Annealing). Also it was found that Mo metal gate was stable up to 90$0^{\circ}C$ with underlying SiO$_2$through X-ray diffraction measurement. Sheet resistances of Mo metal gate obtained from 4-point probe were less than 10$\Omega$/$\square$ that was much lower than those of polysilicon.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.6 s.312
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• pp.27-32
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• 2006

A temperature-compensated hygrometer has been developed using resistive humidity sensors. It consist of a sine wave generator, logarithm converters, rectifiers, and amplifiers. The hygrometer accomplishes the linearization and temperature compensation of sensor characteristics. The theory of operation is presented and experimental results are used to verify theoretical predictions. The experimental results show that the conversion sensitivity of the hygrometer is about 24.8 mV/%RH and the linearity error of the conversion characteristic is less than 17.2 % over a relative humidity range from 30 to 80 %RH. The results also show that the temperature coefficient of the output voltage is less than $10149ppm/^{\circ}C$ over a temperature range from 22 to $40^{\circ}C$.

• Journal of Surface Science and Engineering
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• v.46 no.1
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• pp.16-21
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• 2013

CIGS (Cu-In-Ga-Se) films were deposited on the Mo coated soda lime glass (Mo/SLG) by RF magnetron sputtering using a single sintered target with different chemical compositions. Heat treatment of the CIGS films were carried out under three different conditions, 1step ($350^{\circ}C$ for 2 hour and $550^{\circ}C$ for 2 hour) and 2step ($350^{\circ}C$ for 1 hour and $550^{\circ}C$ for 1 hour). In the case of CIGS films post-annealed on 2step method, grain size remarkably increased compared to other methods, indicating that chemical composition [Cu/(Ga+In) = 1] of CIGS films was same as CIGS target. After heat treatment by 2step method, band gap energy of the CIGS film deposited at RF 80 W showed 1.4 eV which is broadly similar to identical band gap energy (1.2 eV) of CIGS film prepared by evaporation method. Therefore, 2step heat treatment method could be expected to low temperature process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.1
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• pp.47-52
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• 2009

We studied the electrical characteristics of low-k SiOCH interlayer dielectric(ILD) films fabricated by plasma enhanced chemical vapor deposition (PECVD). BTMSM precursor was evaporated and introduced with the flow rates from 16 sccm to 25 sccm by 1 sccm step with the constant flow rate of 60 sccm $O_2$ in process chamber. The vibrational groups of SiOCH thin films were analyzed by FT!IR absorption lines, and the dielectric constant of the low-k SiOCH thin films were obtained by measuring C-V characteristic curves. The heat treatment on SiOCH thin films reduced the FTIR absorption intensity of the Si-O-$CH_3$ bonding group and Si-$CH_3$ bonding group but increased the intensity of Si-O-Si(C) bonding group. The SiOCH ILD films could have low dielectric constant $k\;{\simeq}\;2$ and also be reduced further by decreasing the $CH_3$ group density and increasing Si-O-Si(C) group density through annealing process.