• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 추계학술발표대회 개요집
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• pp.262-264
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• 2005

$Bi_{2}Sr_{2}CaCu_{2}O_{x}$(Bi-2212) and $Bi_{2}Sr_{2}Ca_{2}Cu_{3}O_{y}$(Bi-2223) high-$T_{c}$ superconductor(HTS) coating have been prepared by plasma spraying and heaat treatment. The Bi-2212 HTS coating later is synthesized through the peritectic reaction between Sr-Ca-Cu oxide coating layer and Bi-Cu oxide coating later, and $Bi_{2}Sr_{2}CaCu_{2}O_{y}$(Bi-2212) superconducting phase grow by partial melting process. The superconducting characteristic depends strongly on the conditions of the partial melting process. the Bi-2212 HTS layer consists of the whiskers grown in the diffusion direction. Above the 2212 layer, Bi-2223 phase and secondary phase was observed. The secondary phase is distributed uniformly over the whole surface. This is caused to the microcrack on the coatings surface. Despite everything, the film shows superconducting with an onset $T_{c}$ of about 115K. There are two changes steps. One changes (1step) at 115K is due to the diamagnetism of the Bi-2223 phase and the other changes (2step) at 78K is due to the diamagnetism of the Bi-2212 phase.

• 한국세라믹학회지
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• 제53권2호
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• pp.162-166
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• 2016

0.75BF-0.25BT ceramics were prepared by sintering at $980-1040^{\circ}C$ in air or under atmosphere powder. A sample with 1 mole %-excess $Bi_2O_3$ was also prepared to compensate for $Bi_2O_3$-evaporation. Physical and piezoelectric properties of these three samples were compared. When the sintering temperature increased from $980^{\circ}C$ to $1040^{\circ}C$, the density of the sample sintered in air decreased continuously due to Bi-evaporation. Due to the suppression of Bi-evaporation, the sample sintered under atmosphere powder had a higher density at sintering temperatures above $1000^{\circ}C$ than did the sample sintered in air. The addition of 1 mole %-excess $Bi_2O_3$ successfully compensated for Bi-evaporation and kept the density at the higher value until $1020^{\circ}C$. Grain size increased continuously when the sintering temperature increased from 980 to $1040^{\circ}C$, irrespective of the sintering atmosphere. When the sintering temperature increased, the piezoelectric constant ($d_{33}$) and the electromechanical coupling factor ($k_p$) increased for all samples. The sample with 1 mole % excess-$Bi_2O_3$ showed the highest density and the best piezoelectric properties at sintering temperature of $1020^{\circ}C$.

• 한국전기전자재료학회논문지
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• 제31권4호
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• pp.226-230
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• 2018

Pure $BiFeO_3$ (BFO) and codoped $Bi_{0.9}A_{0.1}Fe_{0.975}Zn_{0.025}O_{3-{\delta}}$ (A=Eu, Dy) thin films were prepared on Pt(111)/Ti/$SiO_2$/Si(100) substrates by chemical solution deposition. The remnant polarizations (2Pr) of the $Bi_{0.9}Eu_{0.1}Fe_{0.975}Zn_{0.025}O_{3-{\delta}}$ (BEFZO) and $Bi_{0.9}Dy_{0.1}Fe_{0.975}Zn_{0.025}O_{3-{\delta}}$ (BDFZO) thin films were about 36 and $26{\mu}C/cm^2$ at the maximum electric fields of 900 and 917 kV/cm, respectively, at 1 kHz. The codoped BEFZO and BDFZO thin films showed improved electrical properties, and leakage current densities of 3.68 and $1.21{\times}10^{-6}A/cm^2$, respectively, which were three orders of magnitude lower than that of the pure BFO film, at 100 kV/cm.

• 한국산학기술학회논문지
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• 제10권2호
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• pp.303-312
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• 2009

본 논문에서는 UWB 통신용 CPW 급전 디스크 섹터 안테나를 설계하고 제작한다. 또한 디스크 섹터 안테나의 부채꼴에 사각형 슬릿을 삽입하여 E-평면에서 방향성을 갖도록 하였다. 안테나의 입력 임피던스는 안테나를 구성하는 파라미터인 디스크 섹터의 반경, 디스크 섹터의 중심각, 접지면의 길이와 급전선 부근의 접지면 모서리의 길이를 변화시켜서 $50{\Omega}$을 갖는 급전선과 정합시켰다. 설계된 UWB 통신용 안테나의 크기는 $72mm{\times}26mm$이고, 시뮬레이션을 통한 안테나의 대역폭은 $3{\sim}13GHz$이다. 측정결과로부터 대역폭은 $1.98{\sim}11GHz$이고 제작된 안테나의 반사손실과 이득은 3.5GHz에서 -50.88dB, 1.34dBi, 5.5GHz에서 -12.27dB, 3.35dBi, 8GHz에서 -23.2dB, 3.8dBi이고 10GHz에서 -16.17dB, 5.2dBi를 갖는다.

• 마이크로전자및패키징학회지
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• 제12권2호
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• pp.95-103
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• 2005

42Sn-58Bi 솔더(이하 wt.$\%$에 의한 표기)와 무전해 Ni-P/치환 Au under bump metallurgy (UBM) 간의 계면 반응을 intermetallic compound (IMC)의 형성과 성장, UBM의 감소, 그리고 범프 전단강도의 영향 관점에서 시효 처리 전 후에 어떠한 변화가 생기는 지를 알아보고자 하였다. 치환 Au 층을 $5{\mu}m$ 두께의 무전해 Ni-P ($14{\~}15 at.\%$ P)위에 세 가지 각기 다른 두께, 즉 $0{\mu}m$(순수한 무전해 Ni-P UBM), $0.1{\mu}m$, $1{\mu}m$로 도금하였다. 그 후 42Sn-58Bi 솔더 범프를 세 가지 다른 UBM 구조에 스크린프린팅 방식으로 형성하였다. 범프 형성 직후에는 세 가지 다른 UBM구조에서 솔더와 UBM 사이에 공통적으로 $Ni_3Sn_4$ IMC (IMC1) 만이 형성됐다. 하지만, 이를 $125^{\circ}C$에서 시효 처리를 할 경우 특이하게 Au를 함유한 UBM 구조에서는 $Ni_3Sn_4$ 위로 또 다른 4원계 화합물 (IMC2)이 관찰되었다. 원자 비로 $Sn_{77}Ni{15}Bi_6Au_2$인 4원계 화합물로 확인되었다. $Sn_{77}Ni{15}Bi_6Au_2$ 층은 솔더 조인트의 접합성에 매우 치명적인 영향을 미쳤다. 시효 처리를 거친 Au를 함유한 UBM 구조에서 솔더 범프의 전단 강도 값은 시효 처리 전에 비해 $40\%$ 이상의 감소를 보였다.

• 센서학회지
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• 제23권6호
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• pp.368-376
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• 2014

In order to measure the segmental impedance of the body, a bioelectrical impedance measurement system (BIMS) using multi-frequency applying method and two-electrode method was implemented in this study. The BIMS was composed of constant current source, automatic gain control, and multi-frequency generation units. Three experiments were performed using the BIMS and a commercial impedance analyzer (CIA). First, in order to evaluate the performance of the BIMS, four RC circuits connected with a resistor and capacitor in serial and/or parallel were composed. Bioelectrical impedance (BI) was measured by applying multi-frequencies -5, 10, 50, 100, 150, 200, 300, 400, and 500 KHz - to each circuit. BI values measured by the BIMS were in good agreement with those obtained by the CIA for four RC circuits. Second, after measuring BI at each frequency by applying multi-frequency to the left and right forearm and the popliteal region of the body, BI values measured by the BIMS were compared to those acquired by the CIA. Third, when the distance between electrodes was changed to 1, 3, 5, 7, 9, 11, 13, and 15 cm, BI by the BIMS was also compared to BI from the CIA. In addition, BI of extracellular fluid (ECF) was measured at each frequency ranging from 10 to 500 KHz. BI of intracellular fluid (ICF) was calculated by subtracting BI of ECF measured at 500 kHZ from BI measured at seven frequencies ranging from 50 to 500 KHz. BI of ICF and ECF decreased as the frequency increased. BI of ICF sharply decreased at frequencies above 300 KHz.

• 한국세라믹학회지
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• 제29권2호
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• pp.161-165
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• 1992

Nonlinear exponents and electron trap density variations were observered in ZnO-Bi2O3-MnO2 ternary ZnO varistors as a function of heat treatment temperature. Three kinds of ZnO varistor compositions were selected; i.e. 99.0 ZnO-0.5 Bi2O3-0.5 MnO2, 98.5 ZnO-1.0 Bi2O3-0.5 MnO2, and 98.0 ZnO-1.5 Bi2O3-0.5 MnO2 in mol%. Sintering was done at 1150$^{\circ}C$ for three hours, and heat treatments were done at 500$^{\circ}C$, 700$^{\circ}C$, and 900$^{\circ}C$. When heat treated at 500$^{\circ}C$, nonlinear exponents were increased regardless of the Bi2O3 amount. Increasing heat treatment temperature above 500$^{\circ}C$ resulted in lowering nonlinear exponents. Nonlinear exponents seem to be related to the 0.17 and 0.33 eV electron traps which are possibly of intrinsic origin.

• Transactions on Electrical and Electronic Materials
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• 제8권2호
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• pp.84-88
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• 2007

[ $Bi_{1.5}Zn_{1.0}Nb_{1.5}O_7$ ] (BZN), $Bi_2Mg_{2/3}Nb_{4/3}O_7$ (BMN), and $Bi_2Cu_{2/3}Nb_{4/3}O_7$ (BCN) pyrochlore thin films were prepared on $Cu/Ti/SiO_2/Si$ substrates by pulsed laser deposition and the micro-structural and electrical properties were characterized for embedded capacitor applications. The BZN, BMN, and BCN films deposited at $25\;^{\circ}C$ and $150\;^{\circ}C$, respectively show smooth surface morphologies and dielectric constants of about $39\;{\sim}\;58$. The high dielectric loss of the films deposited at $150\;^{\circ}C$ compared with films deposited at $25\;^{\circ}C$ was attributed to the defects existing at interface between the films and copper electrode by an oxidation of copper bottom electrode. The leakage current densities and breakdown voltages in 200 nm thick-BMN and BZN films deposited at $150\;^{\circ}C$ are approximately $2.5\;{\times}\;10^{-8}\;A/cm^2$ at 3 V and above 10 V, respectively. Both BZN and BMN films are considered to be suitable materials for embedded capacitor applications.

• 한국재료학회지
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• 제9권4호
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• pp.349-354
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• 1999

Dopant를 첨가하지 않은 시료와 donor dopant로 $CdI_2$를 첨가한 $Bi_2Te_3-10%$ 단결정을 Bridgman법으로 성장시키고 Hall 계수, 전하이동도, 전기비저향, Seebeck 계수, 열전도도 빛 성능지수를 77~600K의 온도범위에서 측정하였다. Dopant를 첨가하지 않은 90% $Bi_2Te_3-10% Bi_2Se_3$ 단결정에서 포화정공농도는 $5.85\times10_{18}cm^{-3}$ 이고 degenerate 온도는 127K 이었￡며, 전하 이동에 대한 산란인자는 -0.23 이고 전자이동도와 정꽁이동도의 비 ($\mu_e/\mu_h)$는 1.45 이었다. 90% $Bi_2Te_3-10% Bi_2Te_3$ 단결정의 OK 에서의 밴드갭 에너지는 0.200 eV 로서 $Bi_2Te_3-Bi_2Se_3$계 단결정에서눈 $Bi_2Se_3$의 놓도가 증가할수록 밴 드갭 에너지가 증가하였다. Donor dopant로 $CdI_2$를 첨가한 90% $Bi_2Te_3-Bi_2Se_3$ 조성의 n형 단결정에서 성능지수의 최대값은 $CdI_2$를 0.05 wt% 첨가한 경우에 약 230K에서 $3.2\times10^{-3}/K$를 나타내었다.

• 한국재료학회지
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• 제19권11호
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• pp.601-606
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• 2009

$BiFeO_3$ (BFO) thin films were prepared on $Pt/TiO_2/Si$ substrate by r.f. magnetron sputtering. The effects of deposition pressure on electrical properties were investigated using measurement of dielectric properties, leakage current and polarization. When BFO targets were prepared, Fe atoms were substituted with Mn 0.05% to increase electrical resistivity of films. (Fe+Mn)/Bi ratio of BFO thin films increases with increasing partial pressure of $O_2$ gas. The deposited films showed the only BFO phase at 10 mTorr, the coexistence of BFO and $Bi_2O_3$ phase at 30-50 mTorr, and the only $Bi_2O_3$ phase at 70 mTorr. The crystallinity of BFO films was reduced due to the higher Bi contents and the decrease of surface mobility of atoms at high temperature. The porosity and surface roughness of films increased with the increase of the deposition pressure. The films deposited at high pressure showed low dielectric constant and high leakage current. The dielectric constant of films deposited at various deposition pressures was 84${\sim}$153 at 1 kHz. The leakage current density of the films deposited at 10${\sim}$70 mTorr was about $7{\times}10.6{\sim}1.5{\times}10.2A/cm^2$ at 100 kV/cm. The leakage current was found to be closely related to the morphology and composition of the BFO films. BFO films showed poor P-E hysteresis loops due to high leakage current.