Intrinsic Quasi 1-D Lattice Instability and
Thermoelectricity
y in In4Se33-δδ
Jong-Soo
g
Rhyee,
y , C. Cho,, K. H. Lee,, S. M. Lee,, S. I. Kim,,
J. H. Shim1, Y. S. Kwon2, and Gabriel Kotliar3
Materials Research Center,, Samsung
g Advanced Institute of Technology
gy
1Dept. of Chemistry, Pohang University of Science and Technology
2Dept. of Physics, Sung Kyun Kwan University
3Dept.
p of Physics
y
and Astronomy,
y Rutgers
g
University,
y USA
Low Thermal Conductivity and CDW
Extremely low thermal conductivity
- 2-D layered WSe2 thin film
- Disordered
Di
d
d llayered
d structure
t
t
- κ=0.04 W/mK
Crystal structure of WSe2
C. Chritescue et al. Science (2007)
Charge Density Wave
* Limitations
- Thin film structure
- Electrical insulator
Charge Density Wave (CDW)
- Strong electron
electron-phonon
phonon coupling
- Density wave energy gap
- Low D Lattice instability
ψ k (ε )
(0)
a-2b
2
2a
a+2b
E =∑
2
k
k '≠ k
k V k'
(0) 2
Ek0 − Ek0'
2nd order
d perturbation
t b ti th
theory
The 7th Korea-US Nano Forum
Iwha Women’s Univ., 6th April 2010
Thermoelectric properties of CDW
Toy model – CeTe2
CeTe2
-High TCDW
-Lattice
Lattice
distortion
along the
plane of CDW
K. Y. Shin et al.
Phys. Rev. B (72)
85132 (2005)
Crystal structure of CeTe2
CeTe2 electron diffraction
Te-layer distortion
Thermoelectricity in CeTe2
- Low thermal
conductivity
- Low
L
Seebeck
coefficient
2
Energy (eV)
1
0
-1
-2
Z Γ
X
M
Γ
Energy band
structure of CeTe2
J. S. Rhyee et al.
J. Appl. Phys. (105)
53712 (2009)
Th
Thermal
l conductivity
d ti it (l
(left)
ft) and
dS
Seebeck
b k coefficient
ffi i t off C
CeTe
T 2-xSn
S x
The 7th Korea-US Nano Forum
Iwha Women’s Univ., 6th April 2010
Peierls distortion and Thermoelectricity
Quasi-1D Bulk crystal
Quasi 1-D In chain in In4Se3 (100) plane
O. A. Balitskii et al.
Y. B. Losovyj et al. Appl. Phys. Lett. (92) 122107 (2008)
Physica E (22) 921 (2004)
Crystal structure and TE properties of In4Se3-x
ab-plane
bc-plane
I 4Se
In
S 3 crystall structure
- Se-deficiency
induced Peierls
distortion
- Low thermal
conductivity along the
plane of Peierls
instability
- High ZT (1.48
@705 K) for n-type
J. S. Rhyee et al. Nature
materials
(
(2009)
)
The 7th Korea-US Nano Forum
Iwha Women’s Univ., 6th April 2010
Peierls distortion and Thermoelectricity
Band structure and Peierls distortion
2
d2
1
1
Energy (eV)
E
En
nergy (eV)
c
0
-1
-1
-2
X Γ
TEM and ED of In4Se2.78 along the ab- (a)
and bc-planes (b).
0
-2
ZT
Y SX
UR
X Γ
ZT
Y SX
UR
(c) In4Se3 and (d) In4Se2.75 band structure
- Quasi 1-D lattice distortion along the baxis
- Lattice doubling in electron diffraction
and generalized electron susceptibility
calculation
- Semiconducting band gap of In4Se3
- Dispersive electron band and localized
J. S. Rhyee et al.
hole band of In4Se2.75
Fermii surface
F
f
(a)
( ) and
d generalized
li d electron
l t
susceptibility
tibilit (b) off
In4Se2.75
Nature (2009)
APL (2009)
The 7th Korea-US Nano Forum
Iwha Women’s Univ., 6th April 2010
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
electron-hole
hole band; hole localization
3. High thermoelectric performance and Peierls distortion
•
•
Peierls distortion of In4Se3-δ
High
g thermoelectric figure-of-merit
g
((ZT 1.48 @ 705 K))
Conclusions
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