evaluation systems of thermoelectric properties of ......evaluation systems of thermoelectric...

Evaluation systems of thermoelectric properties of electrochemically deposited

Bi2Te3 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

ドーピング制御

化合物組成比探索

人工超格子

移動度大の

化合物半導体

ラットリング

スクッテルダイト系

クラスレート系

ハーフホイスラ系

ｆ電子強相関系

多結晶体制御

固溶体系

量子効果

性能指数 S：ゼーベック係数（µV/K）

ρ:比抵抗（Ωm)κ:熱伝導率（W/Km)κρ

2SZ =

ZTSrTiO3

PbSeTe

Bi2Te3/Sb2Te3

材料系

↑プロセス

Film

Bulk

Superlattice Quantum effect Ratlling Poly-crystal Doping Composition

Process control Materials

Com

poun

d se

mic

ondu

ctor

s S

olid

sol

utio

ns

Suk

uttle

dite

C

lath

rate

H

alf-w

hist

ler

Stro

ng c

orel

late

d

κσ TSZT

2

=S：Seebeck coefficient（µV/K） σ：Electrical conductivity (S/m） κ：Thermal conductivity（W/Km） T： Absolute temperature (K)

Dimensionless figure-of-merit

Dilemma between nanotechnology and macro application(waste heat recovery)

Nano technoplogy Micro technology Macro technology

Physics

Computer Science

Material Science

Material Process Try and Error

Device Process

How to overcome the dilemma?

Research Field: “Nanoscience and New Materials for Environmental Challenges”

Cooperative Research Project (2010-2012)

First steps towards the integration of nanowire arrays on practical thermoelectric devices for Energy applications -NANOTHERMA-

FY2009 Strategic Japanese-Spanish Cooperative Program

Goal (1) Developing thermoelectric technologies of nanowire arrays. (2) Finding a hint for a breakthrough of thermoelectric performance.

Synthesis Technology Measurement Technology + Bi-Te nanowire array Quantitative evaluation

Project Leader: Dr. M. Martin-Gonzalez Project Leader: Dr. Y. Shinohara

Instituto Microelectrónica de Madrid National Institute for Materials Science

Spain Japan

Exchange of technology, idea and researchers

Good cooperation in the near future

Samples

Not Annealed 423 K/1 hr

473 K/1 hr 573 K/1 hr

1 μm×20000

Bi2Te3 film Bi2Te3 nanowire array

1.3 cmAlumina template.

120nmφ

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 -5.24µV/K

All resistance measured with probe distance ~ 5 mm

Seebeck coefficient (µV/K) Electrical conductivity (S/cm)

Samples

Experiments

As prepared 423 K 473 K 573 K Substrate Si/Ti/Au

Measured resistance

0.23 Ω 0.14 Ω 0.15 Ω 0.28 Ω 1.81 Ω

Seebeck coefficient

-4.57 µV/K -6.58 µV/K -6.36 µV/K -9.33 µV/K -104.47 µV/K

(273K)

:Heat sink

:Sample stage with thermocouple

:Peltier heater

:Sample

Fig. Sample stage with thermocouple

Thermocouples: T-type 0.127 mmφ Peltier heater: 4cm×４cm Max. input ６W

Experimental Setup for nanowire array (thickness direction)

Seebeck coefficient Standard measurement using Si wafer (thickness 500 μm)

0.0

0.5

1.0

1.5

2.0

0 20 40 60 80 100 120 140

y = 0.012143 + 0.016536x R= 0.99984 Tem

pera

ture

def

eren

ce /

KInput power of heater x / mW

Fig. Temperature difference as a function of input power.

Fig. Home-made apparatus of nanowire array measurement

T

empe

ratu

re d

iffer

ence

/K

-600

-450

-300

-150

0

0 0.5 1 1.5 2 2.5 3

y = -5.9169 - 186.38x R= 0.99997

Tot

al th

erm

oele

ctri

c po

wer

/ μ

VDelta T / K

-600

-500

-400

-300

-200

-100

0

0 0.5 1 1.5 2 2.5 3

Tot

al th

erm

oele

ctri

c po

wer

/ μ

V

Delta T / K

⊿T ⊿T

Ssi=-179.96 μVK-1

Seebeck coefficient of standard measurement using Si wafer

Fig. Relationship between deltaT and total thermoelectric power(TPtotal) in thickness direction of Si.

Fig. Relationship between deltaT and total thermoelectric power(TPtotal) in planar direction of Si.

Good matching between in-plane and thickness setups

In-plane setup Thickness setup

T

herm

oele

ctro

mot

ive

forc

e /µ

V

T

herm

oele

ctro

mot

ive

forc

e /µ

V

Ssi=-184.52 μVK-1

Seebeck coefficient and electrical conductivity of Bi2Te3 nanowire array

0

5

10

15

20

25

0 5 10 15 20 25 30 35

The

rmoe

lect

ric

pow

er /

μV

Input power of heater / mW

厚さ60 μm

Fig. Thermoelectric power as a functionof input power.

S=12µV/K

T

herm

oele

ctro

mot

ive

forc

e /µ

V

Seebeck coefficient of films

0

5 10-5

1 10-4

2 10-4

2 10-4

0 5 10-6 1 10-5 1.5 10-5 2 10-5 2.5 10-5

y = 3.5e-7 + 7.708x R= 0.99991

Vol

tage

/ V

Current / A

141079.1 −−×= Scmσ

Fig. I-V curve of nanowire-array.

1.3 cmAlumina template.

Good cooperation in the near future

Research Field: “Nanoscience and New Materials for Environmental Challenges”

Cooperative Research Project (2009-2012)

First steps towards the integration of nanowire arrays on practical thermoelectric devices for Energy applications -NANOTHERMA-

FY2009 Strategic Japanese-Spanish Cooperative Program

Synthesis Technology Measurement Technology + Bi-Te nanowire array Quantitative evaluation

Project Leader: Dr. M. Martin-Gonzalez Project Leader: Dr. Y. Shinohara

Instituto Microelectrónica de Madrid National Institute for Materials Science

Spain Japan

Exchange of technology, idea and researchers

Good results by good collaboration 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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