• 한국재료학회지
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• 제13권2호
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• pp.69-73
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• 2003

In this work, $IrO_2$thin films as bottom electrode of ferroelectric capacitors were deposited and characterized. The $IrO_2$films deposited in the conditions of 25, 40 and 50% oxygen ambient by sputtering method were annealed at 600, 700 and $800^{\circ}C$, respectively. It was found that the crystallinity and the surface morphology of $IrO_2$films affected the surface properties and electrical properties of SBT thin films prepared by the MOD method. With increasing temperature, the crystallinity and the roughness of $IrO_2$films were also increasing. This increasing of roughness degraded the surface properties and electrical properties of SBT films. We found an optimum condition of $IrO_2$films as bottom electrode for ferroelectric capacitor at 50% oxygen ambient and $600^{\circ}C$ annealing temperature. Electrical characterizations were performed by using$ IrO_2$bottom electrodes grown at an optimum conditions. The remanent polarization ($P_{r}$) of the Pt/SBT/$IrO_2$/$SiO_2$/Si structure was 2.75 $\mu$C/$\textrm{cm}^2$ at an applied voltage of 3 V. The leakage current density was $1.06${\times}$10^{-3}$ A/$\textrm{cm}^2$ at an applied voltage of 3 V.

• 센서학회지
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• 제15권1호
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• pp.34-39
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• 2006

This study provides the electrical model of combustible catalytic gas sensor. Physical characteristics such as thermal behavior, resistance change were included in this model. The finite element method analysis for sensor device structure showed that the thermal behavior of sensor is expressed in a simple electrical equivalent circuit that consists of a resistor, a capacitor and a current source. This thermal equivalent circuit interfaces with real electrical circuit using two parts. One is 'power to heat' converter. The other is temperature dependent variable resistor. These parts realized with the analog behavior devices of the SPICE library. The gas response tendency was represented from the mass transferring limitation theory and the combustion theory. In this model, Gas concentration that is expressed in voltage at the model, is converted to heat and is flowed to the thermal equivalent circuit. This model is tested in several circuit simulations. The resistance change of device, the delay time due to thermal capacity, the gas responses output voltage that are calculated from SPICE simulations correspond well to real results from measuring in electrical circuits. Also good simulation result can be produced in the more complicated circuit that includes amplifier, bios circiut, buffer part.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권10호
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• pp.438-442
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• 2005

Si nanocrystal (Si NC) memory device has several advantages such as better retention, lower operating voltage, reduced punch-through and consequently a smaller cell area, suppressed leakage current. However, the physical and electrical reasons for this behavior are not completely understood but could be related to interface states of Si NCs. In order to find out this effect, we characterized electrical properties of Si NCs embedded in a SiO$_{2}$ layer by scanning probe microscopy (SPM). The Si NCs were generated by the laser ablation method with compressed Si powder and followed by a sharpening oxidation. In this step Si NCs are capped with a thin oxide layer with the thickness of 1$\~$2 nm for isolation and the size control. The size of 51 NCs is in the range of 10$\~$50 m and the density around 10$^{11}$/cm$^{2}$ It also affects the interface states of Si NCs, resulting in the change of electrical properties. Using a conducting tip, the charge was injected directly into each Si NC, and the image contrast change and dC/dV curve shift due to the trapped charges were monitored. The results were compared with C-V characteristics of the conventional MOS capacitor structure.

• 한국재료학회지
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• 제23권11호
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• pp.643-648
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• 2013

Activated carbon (AC) was synthesized from rice husks using the chemical activation method with KOH, NaOH, a combination of (NaOH + $Na_2CO_3$), and a combination of (KOH + $K_2CO_3$) as the chemical activating reagents. The activated carbon with the highest surface area (around $2000m^2/g$) and high porosity, which allows the absorption of a large number of ions, was applied as electrode material in electric double layer capacitors (EDLCs). The AC for EDLC electrodes is required to have a high surface area and an optimal pore size distribution; these are important to attain high specific capacitance of the EDLC electrodes. The electrodes were fabricated by compounding the rice husk activated carbons with super-P and mixed with polyvinylidene difluoride (PVDF) at a weight ratio of 83:10:7. AC electrodes and nickel foams were assembled with potassium hydroxide (KOH) solution as the electrolyte. Electrochemical measurements were carried out with a three electrode cell using 6 M KOH as electrolyte and Hg/HgO as the reference electrode. The specific capacitance strongly depends on the pore structure; the highest specific capacitance was 179 F/g, obtained for the AC with the highest specific surface area. Additionally, different activation times, levels of heating, and chemical reagents were used to compare and determine the optimal parameters for obtaining high surface area of the activated carbon.

• 한국ITS학회 논문지
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• 제14권6호
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• pp.117-124
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• 2015

본 논문에서는 새로운 기법의 광대역 저손실 CRLH(composit right/left handed) 전송선로와 윌킨슨 전력 분배기에 대해 제안한다. 전송선로는 평형 미엔더 인덕터와 직렬 캐패시터로 구성된 coplanar 도파관 (CPW)으로 구성되며, 전력 분배기는 CRLH 전송선로를 일반 전송선로 부분에 대체하여 설계를 한다. 실험 결과 동작 주파수 대역 8.4 GHz 에서 30.0 GHz내에서 반사손실은 12 dB 이하로써 비교적 만족한 결과를 얻었다. 전력 분배기의 주파수는 12.05에서 13.15 GHz 그리고 16.50에서 19.30 GHz 로써 대역폭은 20 dB 기준으로 8.9 % 및 17.9 % 이며 이는 측정결과와 시뮬레이션 결과와 비교를 하였을 때 상당히 일치하는 것을 알 수 있다.

• 대한전자공학회논문지SD
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• 제45권1호
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• pp.28-36
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• 2008

이번 논문은 implantable cardiac 페이스메이커의 검출 단 로서 저전압, 저전력 단일-비트 삼차 델타-시그마 모듈레이터를 구현하였다. 1V이하의 전원 전압에서 효과적으로 동작하기 위하여 distributed feedforward구조와 벌크-드리븐 OTA를 활용하였다. 설계된 모듈레이터는 0.8V의 전원 전압에서 49dB의 dynamic range를 가지면서 816nW의 파워를 소모하였다. 파워 소모를 획기적으로 줄임으로서 페이스메이커뿐만 아니라 제한된 배터리에서 동작하는 implantable 의료 기기에서 다양한 활용이 가능할 것으로 생각된다. 본 모듈레이터의 칩 크기는 $1000{\mu}m{\times}500{\mu}m$로서 $0.18{\mu}m$ CMOS standard 공정으로 제작되었다.

• 한국전자파학회논문지
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• 제26권12호
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• pp.1044-1049
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• 2015

본 논문에서는 격리도 향상 공진기(isolating resonator)를 사용하여 격리도를 향상시킨 안테나를 제안하였다. Wi-Fi 주파수(2.4~2.5 GHz) 대역에서 동작하는 두 개의 루프 안테나는 그라운드의 센터를 중심으로 대칭으로 설계되었고, 이격거리가 매우 가깝다. Wi-Fi 주파수 대역에서의 격리도 저하 특성을 개선하기 위해 두 안테나 사이에 격리도 향상 공진기를 삽입하였다. 제안된 격리도 향상 공진기는 슬롯타입 구조로 공진기의 사이즈 조절을 통해 격리도 특성을 향상시키고, 삽입된 커패시터($C_D$)를 통해 공진기의 공진 주파수를 이동시킴으로써 목표 주파수에서의 격리도 특성을 쉽게 향상시킬 수 있다.

• 한국전자파학회논문지
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• 제21권12호
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• pp.1447-1453
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• 2010

본 논문에서는 두 개의 이중 모드 공진기를 이용하여 이중 대역 통과 필터를 구현하였다. 단락 스터브를 이용한 이중 모드 공진기는 inter-digital 커패시터와 계단형 임피던스를 이용하여 소형화 되었다. 두 개의 이중 모드 공진기는 각 통과 대역의 중심 주파수에서 동작하도록 설계되었다. 전송 영점이 통과 대역의 상측이나 하측에 위치하여 차단 특성을 향상시킬 수 있다. 이중 대역 동작을 위해 이중 급전 구조를 이용하였다. 제안된 구조는 WLAN 대역인 2.45/5.25 GHz에서 동작하도록 설계 제작되었다. 제안된 이중 대역 통과 필터의 크기는 $10.83\;mm{\times}5.3\;mm$이다.

• 한국안전학회지
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• 제33권4호
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• pp.1-7
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• 2018

This paper is analyzed for the thermal characteristics(1 year) of the 6 components(DC breaker, DC filter(including capacitor and discharge resistance), IGBT(Insulated gate bipolar mode transistor), AC filter, AC breaker, etc.) of a photovoltaic power generation-based PCS(Power conditioning system) below 20 kW. Among the modules, the discharge resistance included in the DC filter indicated the highest heat at $125^{\circ}C$, and such heat resulting from the discharge resistance had an influence on the IGBT installed on the rear side the board. Therefore, risk priority through risk priority number(RPN) of FMEA(Failure modes and effects analysis) sheet is conducted for classification into top 10 %. According to thermal characteristics and FMEA, it is necessary to pay attention to not only the in-house defects found in the IGBT, but also the conductive heat caused by the discharge resistance. Since it is possible that animal, dust and others can be accumulated within the PCS, it is possible that the heat resulting from the discharge resistance may cause fire. Accordingly, there are two options that can be used: installing a heat sink while designing the discharge resistance, and designing the discharge resistance in a structure capable of avoiding heat conduction through setting a separation distance between discharge resistance and IGBT. This data can be used as the data for conducting a comparative analysis of abnormal signals in the process of developing a safety device for solar electricity-based photovoltaic power generation systems, as the data for examining the fire accidents caused by each module, and as the field data for setting component management priorities.

• 한국전기전자재료학회논문지
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• 제22권5호
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• pp.386-389
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• 2009

The electrical characteristics and annealing effects of tunneling dielectrics stacked with $SiO_2$ and $Si_{3}N_{4}$ were investigated. I-V characteristics of band gap engineered tunneling gate stacks consisted of $Si_{3}N_{4}/SiO_2/Si_{3}N_{4}$ (NON), $SiO_2/Si_{3}N_{4}/SiO_2$ (ONO) dielectrics were evaluated and compared with $SiO_2$ single layer using the MOS (metal-oxide-semiconductor) capacitor structure. The leakage currents of engineered tunneling barriers (ONO, NON stacks) are lower than that of the conventional $SiO_2$ single layer at low electrical field. Meanwhile, the engineered tunneling barriers have larger tunneling current at high electrical field. Furthermore, the increased tunneling current through engineered tunneling barriers related to high speed operation can be achieved by annealing processes.