• 마이크로전자및패키징학회지
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• 제6권2호
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• pp.75-81
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• 1999

$CaTiO_3$의 유전적 특성의 문제점을 해결하기 위해 $CaTiO_3$에 복합페로브스카이트 구조를 갖는$ La(Mg_{2/3}Ta_{1/3})O_3$를 고용시켜 마이크로파 유전특성을 조사하였다. XRD분석을 통하여 $CaTiO_3$에 $ La(Mg_{2/3}Ta_{1/3})O_3$를 첨가하면 고용체가 형성되며, 구조적으로는 Orthorhombic구조에서 $ La(Mg_{2/3}Ta_{1/3})O_3$의 첨가량이 증가함에 따라 단사정 대칭의 고용체형으로 바뀌어 가는 것을 확인할 수 있었다. (1-x)$CaTiO_3+xLa(Mg_{2/3}Ta_{1/3})O_3$에서 x값이 0.3일 때 유전율 49, 온도계수+$14ppm/^{\circ}C$, $Q \times f_0$ 값은 17000인 재료를 제조할 수 있었다.

• 한국재료학회지
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• 제30권11호
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• pp.615-620
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• 2020

Oxide semiconductor, represented by a-IGZO, has been commercialized in the market as active layer of TFTs of display backplanes due to its various advantages over a-Si. a-IGZO can be deposited at room temperature by RF magnetron sputtering process; however, additional thermal annealing above 300℃ is required to obtain good semiconducting properties and stability. These temperature are too high for common flexible substrates like PET, PEN, and PI. In this work, effects of microwave annealing time on IGZO thin film and associated thin-film transistors are demonstrated. As the microwave annealing time increases, the electrical properties of a-IGZO TFT improve to a degree similar to that during thermal annealing. Optimal microwave annealed IGZO TFT exhibits mobility, SS, V_th, and V_H of 6.45 ㎠/Vs, 0.17 V/dec, 1.53 V, and 0.47 V, respectively. PBS and NBS stability tests confirm that microwave annealing can effectively improve the interface between the dielectric and the active layer.

• 한국세라믹학회지
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• 제32권1호
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• pp.25-30
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• 1995

The frequenc dependence of magnetic permeability($\mu$r) and dielectric constant($\varepsilon$r) in MHz-GHz frequency range and their relationships with microwave absorbing properties were investigated in sintered and composite Ni-Zn ferrites, respectively. It was confirmed that zero reflection condition was required the real parts of permeability and permittivity in sintered specimen, and the complex permeability, permittivity and dielectric loss tangent in composite specimen. The real part of permittivity varied with the replacement of nickel by manganese in sintered Ni-Zn ferrite. Therefore, we could control the matching frequency and matching thickness.

• 한국통신학회논문지
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• 제14권4호
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• pp.321-328
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• 1989

유한요소법을 이용하여 유전체 도파관의 전파특성을 해석하였다. 자계 3성분에 의한 변분표현방식 Galerkin법을 적용하여 주파수를 파라메터로 해서 전파정수를 구하는 유한요소 표시식을 제안하였다. 이 방법은 조건을 고려해서 해석한 결과 spurious 해는 전혀 나타나지 않았으며 이론치와 잘 일치하였다. 이 해법이 타당성을 확인하기 위하여 부분적으로 유전체가 채워직 구형도파관에 적용하여 수치해석 결과를 다른해석 결과와 비교하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.382-385
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• 2001

In the previous study, a new LTCC material in the $PbWO_{4}-TiO_{2}-B_{2}O_{3}-CuO$ system was introduced. The developed material can be sintered at $850^{\circ}C$ and its dielectric properties are $\varepsilon_{r}=20-25$, $Q{\times}f_{o}=30000\sim50000GHz$, and $\tau_{f}=0.2{\sim}30ppm/^{\circ}C$, respectively. Therefore this material can be used as a LTCC substrate material for fabrication of multilayered high frequency communication module set. In present study, using this material, tape casting condition was established. With this condition, a multilayered resonator was fabricated and its electrical properties were examined. In present study, an antenna-duplexer module was also fabricated. Frequency characteristics of as-fabricated antenna-duplexer module was compared with simulation results.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.382-385
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• 2001

In the previous study, a new LTCC material in the PbWO$_4$-TiO$_2$-B$_2$O$_3$-CuO system was introduced. The developed material can be sintered at 850$^{\circ}C$ and its dielectric properties are $\varepsilon$$\sub$r/=20-25, Qxf$\sub$o/=30000∼500000Hz, and $\tau$$\sub$f/=0.2∼30ppm/$^{\circ}C$, respectively Therefore this material can be used as a LTCC substrate material for fabrication of multilayered high frequency communication module set. In present study, using this material, tape casting condition was established. With this condition, a multilayered resonator was fabricated and its electrical properties were examined. In present study, an antenna-duplexer module was also fabricated. Frequency characteristics of as-fabricated antenna-duplexer module was compared with simulation results.

• 한국재료학회지
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• 제12권6호
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• pp.458-463
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• 2002

Carbon nanotubes were synthesized at various conditions using Ni-catalytic thermal chemical vapor deposition method and their characteristic properties were investigated by SEM, TEM and Raman spectroscopy. Carbon nanotubes were formed on very fine Ni-catalytic particles. The carbon nanotubes synthesized by thermal decomposition of acetylene at $700^{\circ}C$ had a coiled shape, while those synthesized at $850^{\circ}C$ showed a curved and Y-shape having a bamboo-like morphology. It was found that the carbon nanotube was also made on the fine Ni-catalytic particles formed on the surface of 100~400nm sized large ones after pretreatment with $NH_3$.ber composites show the high dielectric constant and large conduction loss which is increased with anisotropy of fiber arrangement. It is, therefore, proposed that the glass and carbon fiber composites can be used as the impedance transformer (surface layer) and microwave reflector, respectively. By inserting the foam core or honeycomb core (which can be treated as an air layer) between glass and carbon fiber composites, microwave absorption above 10 dB (90% absorbance) in 4-12 GHz can be obtained. The proposed fiber composites laminates with sandwitch structure have high potential as lightweight and high strength microwave absorbers.

• 대한전자공학회논문지TC
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• 제40권2호
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• pp.70-77
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• 2003

본 논문에서는 초고주파 대역의 패키징을 위한 동축커넥터와 마이크로스트립의 전이 구조를 해석하고 측정하였다. 현재까지 여러 가지 전이구조의 최적화에 대한 연구는 활발히 이루어졌다. 하지만 주로 특정 전송 선로에 대해서만 개선되어져 왔기 때문에 그 적용범위가 매우 좁다. 따라서 본 논문에서는 상용화되고 있는 비유전율이 2, 5, 10인 세 종류의 기판을 모델로 해석하였다. 또한 FEM 해석의 신뢰성을 확인 후 전이부 분의 등가회로 모델을 추출하고, 추출된 물리적인 값들을 결정 하는 요인을 찾아내고 최적의 전이 특성을 위한 전자기적 변수들을 확인하였다. 더불어 기판 유전율과 마이크로스트림 구조를 기준으로 최적의 전이특성을 내는 전이구조를 제시하였다. 본 논문의 결과는 마이크로파 패키징 개발에서 동축커넥터와 마이크로스트립 최적의 전이구조 설계에 효과적으로 활용 될 수 있으리라 기대된다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.379-382
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• 1998

In this paper, the microwave dielectric properties of the yPb($Fe_{2/3}W_{1/3}$)$O_{3}$ - (1-y)($Pb_{x}Ca_{1-x}$)$ZrO_{3}$ system were investigated. It was found that an addition of Pb($Fe_{2/3}W_{1/3}$)$O_{3}$ promotes the grain growth, the solid solution between the Pb-based perovskite and the Ca-based perovskite and the decreasing of the sintering temperature. Especially, we found that 0.05Pb($Fe_{2/3}W_{1/3}$)$O_{3}$-0.95($Pb_{x}Ca_{1-x}$)$ZrO_{3}$ ceramic has not only lower sintering temperature but also better dielectric properties than those of the (Pb, Ca)$ZrO_{3}$ systems.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.28-28
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• 2007

Ferroelectric $(Ba_{0.5}Sr_{0.5})TiO_3$ (BST) thin films of thickness 500nm were deposited on $LaAlO_3$, (LAO) substrates by at $800^{\circ}C$. BST films were characterized for structure using X-ray diffraction (XRD). The surface morphology and thickness of BST the films were characterized by atomic force microscopy (AFM) and field emission scanning electron microscope (FESEM). We measured the dielectric properties at microwave frequencies (1~3 GHz) using a symmetrical stripline resonator with shorted ends and terahertz frequencies (0.2~2.5 THz) using a time-domain terahertz spectroscopy. The real and imaginary parts of the complex dielectric constant of the BST thin films on LAO substrates were in agreement with those previously reported.