마그네트론 스퍼터링법으로 제조한 P형 (Bi₁-xSbx)₂Te₃ 박막의 결정성과 열전특성

연대중(Dae Joong Yeon),오태성(Tae Sung Oh) 한국진공학회(ASCT) 2000 Applied Science and Convergence Technology Vol.9 No.4

마그네트론 스퍼터링법으로 p형 (Bi_(0.15)Sb_(0.82))₂Te₃과 (Bi_(1-x)Sb_x)₂Te₃ 열전박막을 제조하여 스퍼터 증착조건 및 Sb₂Te₃ 함량에 따른 열전특성을 분석하였다. Coming glass 기판을 10 rpm으로 회전시키며 DC 스퍼터링법으로 300℃에서 증착한(Bi_(0.15)Sb_(0.82))₂Te₃ 박막은 (Bi,Sb)₂Te₃ 단일상으로 결정화가 완료되고 c축 우선배향성을 나타내었으며, 다른 조건으로 증착한 (Bi_(0.15)Sb_(0.82))₂Te₃ 박막보다 높은 185 ㎶/K의 Seebeck 계수를 나타내었다. p형 (Bi_(1-x)Sb_x)₂Te₃ (0.77≤x≤1.0) 박막에서는 Sb₂Te₃ 함량이 증가함에 따라 Seebeck 계수와 전기비저항이 감소하였으며 (Bi_(0.05)Sb_(0.95))₂Te₃ 조성에서 0.79×10^(-3) W/K²-m의 최대 출력인자를 나타내었다. (Bi_(0.15)Sb_(0.85))₂Te₃ and (Bi_(1-x)Sb_x)₂Te₃ thermoelectric thin films were prepared by magnetron sputtering process, and their thermoelectric characteristics were investigated with variation of the sputtering condition and the Sb₂Te₃ content. The (Bi_(0.15)Sb_(0.85))₂Te₃ film, deposited by DC sputtering at 300℃ with rotating the Coming glass substrate at 10 rpm, was fully crystallized to (Bi,Sb)₂Te₃ phase with c-axis preferred orientation. This (Bi_(0.15)Sb_(0.85))₂Te₃ film exhibited the Seebeck coefficient of 185 ㎶/K which was higher than the values of other (Bi_(0.15)Sb_(0.85))₂Te₃ films fabricated with different sputtering conditions. With increasing the Sb₂Te₃ content, the Seebeck coefficient and electrical resistivity of p-type (Bi_(1-x)Sb_x)₂Te₃ (0.77≤x≤1.0) film were lowered. Among p-type (Bi(1-x)Sb_x)₂Te₃ films, a maximum power factor of 0.79×10^(-3) W/K²-m was obtained at (Bi_(0.05)Sb_(0.95))₂Te₃ composition.

Bi 함량에 따른 SrBi2xTa₂O9 박막의 전기적 특성

연대중(Dae Joong Yeon),권용욱(Yongwook Kwon),박주동(Joo Dong Park),오태성(Tae Sung Oh) 한국진공학회(ASCT) 1999 Applied Science and Convergence Technology Vol.8 No.3(1)

MOD 공정으로 SrBi_(2x)Ta₂O_9 (SBT) 박막을 제조하여 Bi/Ta 몰비 x에 따른 강유전 특성과 누설전류 특성을 분석하였다. Bi/Ta 몰비가 증가함에 따라 SBT 박막의 결정립 크기가 증가하였으며, x=0.8~1.2 조성의 박막은 등축정으로 이루어져 있었으나 x=l.4 및 x=1.6 조성의 박막에서는 침상 형태의 결정립이 관찰되었다. SBT 박막은 Bi/Ta 몰비 x=1.2 조성에서 최적의 강유전 특성을 나타내었으며, 이때 5 V의 인가전압에서 측정한 잔류분극 2P_r과 항전계 E_c는 각기 9.79 μC/㎠와 24.2 ㎸/㎝이었다. Bi/Ta 몰비가 증가함에 따라 SBT 박막의 누설전류밀도가 증가하였다. 후속열처리에 의해 x=1.2 조성 박막의 2P_r과 E_c가 각기 11.3 μC/㎠과 39.6 ㎸/㎝로 증가하였다. Bi/Ta 몰비가 증가함에 따라 후속열처리에 따른 누설전류밀도의 감소 정도가 현격히 증가하여, 후속열처리 전과는 달리 x=1.6 조성에서 가장 낮은 누설전류밀도를 나타내었다. SrBi_(2x)Ta₂O_9 (SBT) thin films were prepared on platinized silicon substrates by MOD process, and their ferroelectric and leakage current characteristics were investigated. The grain size of the MOD-derived SBT films increased with increasing the Bi/Ta mole ratio. Although the SBT films with x of 0.8~1.2 were composed of the equiaxed grains, the elongated grains were also observed for the SBT films with x of 1.4 and 1.6. The SBT film with x of 1.2 exhibited the optimum ferroelectric properties of 2Pr : 9.79 μC/㎠ and E_c : 24.2 ㎸/㎝ at applied voltage of 5 V. The leakage current density of the SBT films increased with increasing the Bi/Ta mole ratio. With post annealing process, 2P_r and E_c of the SBT film with x of 1.2 increased 11.3 μC/㎠ and 39.6 ㎸/㎝, respectively. Decrement of the leakage current density by post annealing process increased remarkably with increasing the Bi/Ta mole ratio, and the SBT film with x=1.6 exhibited the lowest leakage current density after post annealing process.

후속 열처리에 따른 Pt / SBT / Pt 캐패시터의 강유전 특성과 누설전류 특성

권용욱(Yongwook Kwon),박주동(Joo Dong Park),연대중(Dae Joong Yeon),오태성(Tae Sung Oh) 한국진공학회(ASCT) 1999 Applied Science and Convergence Technology Vol.8 No.3(1)

MOD 공정으로 제조한 SrBi₂.₄Ta₂O_9 (SBT) 박막으로 Pt/SBT/Pt 캐패시터를 형성하여, 400~800℃ 범위에서의 후속 열처리에 따른 강유전 특성 및 누설전류 특성의 변화 거동을 분석하였다. 후속 열처리 전의 SBT 박막은 leaky한 박막의 전형적인 분극이력곡선을 나타내었으나, 550~800℃에서 후속 열처리함에 따라 분극이력 특성이 현저히 향상되어 잘 발달된 강유전 이력곡선을 얻을 수 있었다. Pt/SBT/Pt 캐패시터는 600℃에서 후속 열처리시 잔류분극 2Pr이 9.72 μC/㎠의 최대값을 나타내었으며, 그 이상의 온도에서는 후속 열처리 온도의 증가에 따라 2P_r이 감소하였다. 후속 열처리 전의 SBT 박막은 75 ㎸/㎝의 전계에서 10^(-3) A/㎠의 높은 누설전류밀도를 나타내었으나, 600~800℃에서 후속 열처리함에 따라 누설전류밀도가 10^(-6) A/㎠ 이하로 현저히 감소하였다. Pt/SBT/Pt capacitors were fabricated using the MOD-derived SrBi₂.₄Ta₂O_9 (SBT) films, and their ferroelectric and leakage current characteristics were investigated with post annealing at 400~800℃. Although the MOD-derived SBT film exhibited the hysteresis loop typical for the leaky film, the well-saturated ferroelectric hysteresis loop could be obtained by post annealing the Pt/SBT/Pt capacitors at 550~800℃. The remanent polarization 2P_r of the SBT film exhibited a maximum value of 9.72 μC/㎠ with post annealing at 600℃, and then decreased with increasing the post annealing temperature above 600℃. The MOD-derived SBT films exhibited the high leakage current density of ~10^(-3) A/㎠ at 75 ㎸/㎝. With post annealing the Pt/SBT/Pt capacitor at 600~800℃, however, the leakage current density decreased remarkably to less than 10^(-6) A/㎠ at 75 ㎸/㎝.

LSMCD 공정으로 제조한 SBT 박막의 두께에 따른 강유전 특성

박주동(Joo Dong Park),권용욱(Yongwook Kwon),연대중(Dae Joong Yeon),오태성(Tae Sung Oh) 한국진공학회(ASCT) 1999 Applied Science and Convergence Technology Vol.8 No.3(1)

LSMCD (Liquid Source Misted Chemical Deposition) 공정으로 Pt/Ti/SiO₂/Si 기판상에 70~150 ㎚ 두께의 SrBi₂.₄Ta₂O_9 (SBT) 박막을 제조하여, 박막 두께에 따른 미세구조, 강유전 특성과 누설전류 특성을 분석하였다. 70~150 ㎚ 두께 범위의 SBT 박막은 800℃에서 1시간 동안 산소분위기 열처리함으로써 모두 우선방향성이 없는 다결정 박막으로 결정화되었으며, 박막 두께에 무관하게 ~100 ㎚ 크기의 결정립으로 이루어져있었다. SBT 박막의 두께가 감소함에 따라 잔류분극 2P_r과 항전계 E_c가 증가하였으며, 70 ㎚ 두께의 SBT 박막은 5V의 구동전압에서 17.8 μC/㎠의 잔류분극 2P_r과 74 ㎸/㎝의 항전계 E_c를 나타내었다. LSMCD 공정으로 제조한 SBT 박막은 70~150 ㎚의 두께 범위에서 두께 감소에 따라 비유전율이 감소하는 크기 효과를 나타내었다. 125 ㎚ 이상 두께의 SBT 박막은 5V의 인가전압까지 10^(-7) A/㎠ 이하의 우수한 누설전류 특성을 나타내었다. SrBi₂.₄Ta₂O_9 (SBT) thin films of 70~150 ㎚ thickness were prepared on platinized silicon substrates by Liquid Source Misted Chemical Deposition (LSMCD) process, and their microstructure, ferroelectric and leakage current characteristics were investigated. By annealing at 800℃ for 1 hour in oxygen ambient, SBT films were fully crystallized to the Bi layered perovskite structure without preferred orientation. The grain size of the LSMCD-derived SBT films was about 100 ㎚, and was not varied with the film thickness. 2P_r and E_c of the SBT films increased with decreasing the film thickness, and the 70 ㎚-thick SBT film exhibited 2P, of 17.8 μC/㎠ and E_c of 74 ㎸/㎝ at applied voltage of 5 V. Within the film thickness range of 70~150 ㎚, the relative dielectric permittivity of the LSMCD-derived SBT films decreased with decreasing the film thickness. Leakage current densities lower than 10^(-7) A/㎠ at 5 V were observed in the SBT films thicker than 125 ㎚.

농식품 표준 통합 정보화를 위한 플랫폼 관리 시스템 구축

장대자(Jang Dai-Ja),김희진(Kim Hee-Jin),송유정(Song Yu-Jung),김기연(Kim Kee-Yeun),연대중(Yeon Dae-Joong),김유(Kim Yu) 한국콘텐츠학회 2014 한국콘텐츠학회 종합학술대회 논문집 Vol.2014 No.11

가압소결법으로 제조한 p 형 (Bi0.2Sb0.8)Te3/(Pb0.7Sn0.3)Te 경사기능소자의 발전출력 특성

현도빈,오태성,연대중 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.5

The functional gradient material of p-type (Bi_(0.2)Sb_(0.8))₂Te₃/(Pb_(0.7)Sn_(0.3))Te with the segment ratio of 1.3 : 1 was fabricated by hot pressing of the mechanically alloyed (Bi_(0.2)Sb_(0.8))₂Te₃ and 0.5 at% Na₂Te-doped (Pb_(0.7)Sn_(0.3))Te powders. The power generation characteristics of the hot-pressed (Bi_(0.2)Sb_(0.8))₂Te₃/(Pb_(0.7)Sn_(0.3))Te were measured and compared with those of the (Bi_(0.2)Sb_(0.8))₂Te₃and 0.5 at% Na₂Te-doped (Pb_(0.7)Sn_(0.3))Te alloys. With the temperature difference (ΔT) higher than 300℃ at both ends of the specimen, the hot-pressed (Bi_(0.2)Sb_(0.8))₂Te₃/(Pb_(0.7)Sn_(0.3))Te exhibited larger output power than those of the (Bi_(0.2)Sb_(0.8))₂Te₃ and 0.5 at% Na₂Te-doped (Pb_(0.7)Sn_(0.3))Te alloys. The maximum output power of the (Bi_(0.2)Sb_(0.8))₂Te₃/(Pb_(0.7)Sn_(0.3))Te predicted with the measured Seebeck coefficient and the estimated electrical resistivity was in good agreement with the measured values.

가압소결법으로 제조한 p 형 (Bi0.2Sb0.8)2Te3/(Pb0.7Sn0.3)Te 경사기능소자의 열전특성

이희웅,현도빈,오태성,연대중 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.1

The functional gradient material of p-type (Bi_(0.2)Sb_(0.8))₂Te₃/ (Pb_(0.7)Sn_(0.3))Te with the segment ratio of 1.3 : 1 was fabricated by hot pressing of the mechanically alloyed (Bi_(0.2)Sb_(0.8))₂Te₃ and 0.5 at% Na₂Te-doped(Pb_(0.7)Sn_(0.3))Te powders. The thermoelectric properties of the hot-pressed (Bi_(0.2)Sb_(0.8))₂Te₃/(Pb_(0.7)Sn_(0.3))Te were measured and compared with those of the (Bi_(0.2)Sb_(0.8))₂Te₃ and 0.5 at% Na₂Te-doped (Pb_(0.7)Sn_(0.3))Te alloys. Reaction layer of ∼300 ㎛ thickness was formed at the (Bi_(0.2)Sb_(0.8))₂Te₃/(Pb_(0.7)Sn_(0.3))Te interface. At temperatures ranging from 200℃ to 350℃, the (Bi_(0.2)Sb_(0.8))₂Te₃/(Pb_(0.7)Sn_(0.3))Te functional gradient material exhibited a superior figure-of-merit to those of the (Bi_(0.2)Sb_(0.8))₂Te₃ and the 0.5 at% Na₂Te-doped (Pb_(0.7)Sn_(0.3))Te alloys, implying that the efficiency of thermoelectric energy conversion can be improved by the segment bonding of different thermoelectric materials.