Intrinsic Quasi 1-D Lattice Instability and Thermoelectricity in In 4 - - PowerPoint PPT Presentation

Intrinsic Quasi 1-D Lattice Instability and Thermoelectricity in In4Se3-δ y

4 3 δ

Jong-Soo Rhyee, C. Cho, K. H. Lee, S. M. Lee, S. I. Kim, g y , , , , ,

• J. H. Shim1, Y. S. Kwon2, and Gabriel Kotliar3

Materials Research Center, Samsung Advanced Institute of Technology , g gy

• 1Dept. of Chemistry, Pohang University of Science and Technology
• 2Dept. of Physics, Sung Kyun Kwan University
• 3Dept. of Physics and Astronomy, Rutgers University, USA

p y y g y

Low Thermal Conductivity and CDW Low Thermal Conductivity and CDW

Extremely low thermal conductivity

• 2-D layered WSe2 thin film

Di d d l d t t

• Disordered layered structure
• κ=0.04 W/mK

* Limitations

Crystal structure of WSe2

• C. Chritescue et al. Science (2007)

* Limitations

• Thin film structure
• Electrical insulator

Charge Density Wave Charge Density Wave (CDW)

• Strong electron-phonon coupling

) (ε ψ k Strong electron phonon coupling

• Density wave energy gap
• Low D Lattice instability

k V k

2 ) ( ) (

'

a-2b 2 a+2b

∑

≠

− =

k k k k k

E E k V k E

' ' ) ( ) ( 2

'

2nd d t b ti th

The 7th Korea-US Nano Forum Iwha Women’s Univ., 6th April 2010

2a

2nd order perturbation theory

Thermoelectric properties of CDW Thermoelectric properties of CDW

Toy model – CeTe2

CeTe2

• High TCDW

Lattice

• Lattice

distortion along the plane of CDW Crystal structure of CeTe2 CeTe2 electron diffraction Te-layer distortion

• K. Y. Shin et al.
• Phys. Rev. B (72)

85132 (2005)

Thermoelectricity in CeTe2

2

• Low thermal

conductivity L

• 1

1 Energy (eV)

• Low

Seebeck coefficient

• 2

Γ X M Γ Z

Th l d ti it (l ft) d S b k ffi i t f C T S Energy band structure of CeTe2

• J. S. Rhyee et al.
• J. Appl. Phys. (105)

53712 (2009)

The 7th Korea-US Nano Forum Iwha Women’s Univ., 6th April 2010

Thermal conductivity (left) and Seebeck coefficient of CeTe2-xSnx

Peierls distortion and Thermoelectricity Peierls distortion and Thermoelectricity

Quasi-1D Bulk crystal

Quasi 1-D In chain in In4Se3 (100) plane

• Y. B. Losovyj et al. Appl. Phys. Lett. (92) 122107 (2008)
• O. A. Balitskii et al.

Physica E (22) 921 (2004)

Crystal structure and TE properties of In4Se3-x

• Se-deficiency

induced Peierls

ab-plane bc-plane

induced Peierls distortion

• Low thermal

conductivity along the plane of Peierls I S l

• J. S. Rhyee et al. Nature

( )

plane of Peierls instability

• High ZT (1.48

@705 K) for n-type materials

The 7th Korea-US Nano Forum Iwha Women’s Univ., 6th April 2010

In4Se3 crystal structure

(2009)

materials

Peierls distortion and Thermoelectricity Peierls distortion and Thermoelectricity

Band structure and Peierls distortion

2 2

c d

1 Energy (eV) 1 nergy (eV)

• 2
• 1

E

X R U X S Y T Z

Γ

• 2
• 1

X R U X S Y T Z

Γ En

(c) In4Se3 and (d) In4Se2.75 band structure TEM and ED of In4Se2.78 along the ab- (a) and bc-planes (b).

• Quasi 1-D lattice distortion along the b-

axis

• Lattice doubling in electron diffraction

and generalized electron susceptibility calculation

• J. S. Rhyee et al.

Nature (2009) APL (2009)

F i f ( ) d li d l t tibilit (b) f

• Semiconducting band gap of In4Se3
• Dispersive electron band and localized

hole band of In4Se2.75

The 7th Korea-US Nano Forum Iwha Women’s Univ., 6th April 2010 APL (2009)

Fermi surface (a) and generalized electron susceptibility (b) of In4Se2.75

Summary and Conclusions Summary and Conclusions

Summary

• 1. Low thermal conductivity
• Extremely low thermal conductivity in the layered structure of disordered plane
• CDW is an effective way to realize the disordered and layered structure

2. Band structural property of In4Se3-δ

• Asymmetric electron hole band; hole localization
• Asymmetric electron-hole band; hole localization

3. High thermoelectric performance and Peierls distortion

• Peierls distortion of In4Se3-δ
• High thermoelectric figure-of-merit (ZT 1.48 @ 705 K)

Conclusions

g g ( @ )

Possible practical application for waste heat power generation of In4Se3-δ Peierls distortion is a new pathway of thermoelectric materials development

The 7th Korea-US Nano Forum Iwha Women’s Univ., 6th April 2010