Evaluation systems of thermoelectric properties of electrochemically deposited Bi 2 Te 3 films and nanowire arrays Yoshikazu Shinohara*, Marisol Martin-Gonzalez** * National Institute for Materials Science, Japan ** Instituto Microelectrónica de Madrid, Spain
The state of arts of thermoelectric materials Dimensionless figure-of-merit S ： Seebeck coefficient （ µ V / K ） σ T 2 S S ：ゼーベック係数（ µ V/K ） = 性能指数 σ ： Electrical conductivity (S/m ） ZT κ κ ： Thermal conductivity （ W/Km ） ρ : 比抵抗（ Ω m) 2 S Z = T ： Absolute temperature (K) κ : 熱伝導率（ W/Km) ρ κ Bi 2 T e 3 /Sb 2 T e 3 SrTiO 3 Film 人工超格子 Superlattice 量子効果 ZT Quantum effect ラットリング PbSeT e Ratlling Bulk 多結晶体制御 Poly-crystal ドーピング制御 Doping 化合物組成比探索 Composition ↑ Compound semiconductors Solid solutions Sukuttledite Clathrate Half-whistler Strong corellated 化合物半導体 移動度大の ス クラス ハ ｆ プロセス 固溶体系 Process control ーフ 電子強相関系 クッ Materials 材料系 テル ホイス レ ート ダイト ラ系 系 系
How to overcome the dilemma? Nano technoplogy Micro technology Macro technology Physics Computer Science Material Science Material Process Try and Error Device Process Dilemma between nanotechnology and macro application(waste heat recovery)
FY2009 Strategic Japanese-Spanish Cooperative Program Research Field: “Nanoscience and New Materials for Environmental Challenges” Spain Japan Instituto Microelectrónica de Madrid National Institute for Materials Science + Synthesis Technology Measurement Technology Quantitative evaluation Bi-Te nanowire array Project Leader: Dr. M. Martin-Gonzalez Project Leader: Dr. Y. Shinohara Cooperative Research Project (2010-2012) First steps towards the integration of nanowire arrays on practical thermoelectric devices for Energy applications -NANOTHERMA- Exchange of technology, idea and researchers Goal (1) Developing thermoelectric technologies of nanowire arrays. Good cooperation in the near future (2) Finding a hint for a breakthrough of thermoelectric performance.
Samples Bi 2 Te 3 film Bi 2 Te 3 nanowire array 120nm φ 1.3 cm 1 μm × 20000 Alumina template. Not Annealed 423 K/1 hr 473 K/1 hr 573 K/1 hr
Experimental Setup for films (in-plane direction)
Measurement of Seebeck coefficient for Standard sample (Pt wire) The measured value agrees well with the reference value of -5.24 µ V/K
Samples Asprepared 423 K 473 K 573 K Substrate (273K) Si/Ti/Au Experiments Measured 0.23 Ω 0.14 Ω 0.15 Ω 0.28 Ω 1.81 Ω resistance Seebeck -4.57 µV/K -6.58 µV/K -6.36 µV/K -9.33 µV/K -104.47 µV/K coefficient All resistance measured with probe distance ~ 5 mm Seebeck coefficient ( µ V/K) Electrical conductivity (S/cm)
Experimental Setup for nanowire array (thickness direction) Thermocouples: T-type 0.127 mm φ Peltier heater: 4cm × ４ cm Max. input ６ W :Heat sink :Peltier heater Fig. Sample stage with thermocouple :Sample stage with thermocouple :Sample
Seebeck coefficient Standard measurement using Si wafer (thickness 500 μm) 2.0 Temperature difference /K Temperature deference / K 1.5 1.0 0.5 y = 0.012143 + 0.016536x R= 0.99984 0.0 0 20 40 60 80 100 120 140 Input power of heater x / mW Fig. Home-made apparatus of nanowire array measurement Fig. Temperature difference as a function of input power.
Seebeck coefficient of standard measurement using Si wafer In-plane setup Thickness setup 0 0 Thermoelectromotive force / µ V Total thermoelectric power / μ V Thermoelectromotive force / µ V y = = -5. 5.916 169 - - 18 186.3 .38x x R R= 0 0.99 99997 97 Total thermoelectric power / μ V -100 ⊿ T ⊿ T -150 -200 -300 -300 -400 -450 -500 S si =-184.52 μVK -1 S si =-179.96 μVK -1 -600 -600 0 0.5 1 1.5 2 2.5 3 0 0.5 1 1.5 2 2.5 3 Delta T / K Delta T / K Fig. Relationship between deltaT and Fig. Relationship between deltaT and total thermoelectric power(TP total ) total thermoelectric power(TP total ) in thickness direction of Si. in planar direction of Si. Good matching between in-plane and thickness setups
Seebeck coefficient and electrical conductivity of Bi 2 Te 3 nanowire array Thermoelectromotive force / µ V 25 2 10 -4 Thermoelectric power / μV y = 3.5e-7 + 7.708x R= 0.99991 20 2 10 -4 15 Voltage / V 1 10 -4 厚さ 60 μm 10 5 10 -5 5 S=12 µ V/K − − = × 4 1 σ 1 . 79 10 Scm 0 0 5 10 15 20 25 30 35 0 5 10 -6 1 10 -5 1.5 10 -5 2 10 -5 2.5 10 -5 0 Input power of heater / mW Current / A Fig. Thermoelectric power as a function Fig. I-V curve of nanowire-array. of input power. 1.3 cm Alumina template. Seebeck coefficient of films
FY2009 Strategic Japanese-Spanish Cooperative Program Research Field: “Nanoscience and New Materials for Environmental Challenges” Spain Japan Instituto Microelectrónica de Madrid National Institute for Materials Science + Synthesis Technology Measurement Technology Quantitative evaluation Bi-Te nanowire array Project Leader: Dr. M. Martin-Gonzalez Project Leader: Dr. Y. Shinohara Cooperative Research Project (2009-2012) First steps towards the integration of nanowire arrays on practical thermoelectric devices for Energy applications -NANOTHERMA- Exchange of technology, idea and researchers Good results by good collaboration Good cooperation in the near future between Japan and Spain
Acknowledgment • Dr. Yukihiro Isoda • Dr. BISWAPRIYA DEB • Dr. Hiroshi Kawakami • Dr. Olga C. Calero • Dr. Pablo Díaz Chao • Ms. Begona A. Mayor (Best poster award at the Workshop at Toledo in 2011)
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