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Mott FET
ITRS Workshop on Emerging Research Logic DevicesBordeaux, France, September 21, 2012
A. Sawa1,2
S. Asanuma,1,2 P.-H. Xiang,1,2 I. H. Inoue,1,2
H. Yamada,1 H. Sato,1,2 and H. Akoh1,2
1National Institute of Advanced Industrial Science and Technology (AIST)2JST-CREST
Outline
・ Correlated electron system・ Mott metal-insulator transition・ Mott field effect transistor
Feature/potentialIssues/challenges
・ ExperimentsMn-oxidesNi-oxidesV-oxides
・ Summary
Correlated electron system
Band insulator
E
EF
electron
Mott insulator
t
One electron in an orbital due to on-site Coulomb repulsion (U > t)
E
EF
t: TransferU: Coulomb
Pauli’s ruleNo more than 2 electrons in an orbital
E
EF
U
upper Hubbardband (UHB)
lower Hubbardband (LHB)
electron orbital
Mott insulator-metal transition
E
EFW U
Mott insulator Correlated-electron metal
W < U W > UMott transition
W: band widthU: Coulomb energy
E
EF
WU W ∝ t
t
(t < U) (t > U)
electron
Electron solid
Electron liquid
Carrier doping, magnetic field, light, ・・・
Decrease in U (band gap)
10-4
10-2
100
102
104
0 100 200 300
Res
istiv
ity [
cm]
Temperature [K]
Ca1-x
CexMnO
3
x=0
x=0.02
x=0.03
Huge resistance change
Y. Tomioka, unpublished
T
Carrier density
Antiferromagnetic insulator
Critical point
Electronic phasesT
Carrier density
Paramagneticmetal
Quantum CP
(La,Sr)MnO3
250
200
150
100
50
0
ab
(
cm)
6040200
T (K)
La2-xBaxCuO4 x=0.09
0T
9T
Superconductivity
Changes in electronic, magnetic, and optical properties
Optical propertyMagnetizum
Ferromagnetic metal
Antiferromagnetic insulator
insulator
metal
Mott FET
Mott FET
Mott FET can control electronic, magnetic, and optical properties by electric field
Gate
Correlated-electron material
Drain Source
“ON” “ON” “ON”“OFF”
“electronic” “magnetic” “optical”
Mott transition/transistor‐Scaling?‐
Metal
ON
Insulator
OFFMott
transition
Number of electrons 103 electrons
4 nm
In principle, a nanometer-scale Mott insulator shows the Mott transition
No one has demonstrated
Electronsolid
Electronliquid
Kotliar et.al PRL 89, 046401 (2002).
First order phase transitionHysteretic behavior Nonvolatile(?)
V < 0
V > 0
electrode doped-Mott ins.
Oka, Nagaosa, PRL95, 266403 (2005)
Mott transition/transistor‐Nonvolatile?‐
No one has demonstrated
Matsubara et al., PRL99, 207401 (2007)
Reflectcance Electronic state
Karr rotationMagnetic state
Mott transition takes place within a few picoseconds
sample
probe
PBSHWP
Balance Reciever
0.2-3 T
delaypump
sample
probe
PBSHWP
Balance Reciever
0.2-3 T
delaypump
Sample: Gd0.55Sr0.45MnO3
Mott transition/transistor‐Fast switching?‐Ultrafast optical pump‐probe spectroscopy
Challenges
1013 1015
conventional gate dielectric (SiO2): ~1013/cm2
For the realization of a practical Mott transistor, • Correlated-electron materials with a MI transition attainable at
significantly lower carrier concentrations• High-k gate materials with a large breakdown strength
Ahn, Triscone, Mannhart, Nature 424, 1015 (2003).
1014 – 1015 cm-2
Electric double layer transistor
Outer Helmholtz plane
J. T. Ye et al., Nature Mater. 9, 125 (2010)
S. Ono et al., APL 94, 063301 (2009)
a large amount of carriers:1014 – 1015 cm-2(@2V)
Electric double layer transistor
Electrolyte/ionic liquid is used as gate dielectrics
Large capacitance: > 10 mF/cm2
CMO channel Thickness: ~ 30 nm W/L: ~ 10μm/100μm
+ −DEME+ cation TFSI - anion
GD S+ + + +−− − −
Ionic Liquid
Sepa-rator− − − −
CMO
ID IG
VD VG
YAO substrate
10mF/cm2@10-3Hz →1.5 × 1014 /cm2@VG= 2.5 V
Electric double layer transistor (EDLT)
S. Asamuna, AS et al., Appl. Phys. Lett. 97, 142110 (2010)P-.H. Xiang, AS et al., Adv. Mater. 23, 5822 (2011)
Insulator
Metal
Thickness of channel : 40nmOn/Off ratio: >10 @RT >103 @50K
P-.H. Xiang, AS et al., Adv. Mater. 23, 5822 (2011)
-2 -1 0 1 2
-0.1
0.0
0.1
0.00
0.05
0.10
0.15
0.20
0.25
I G (nA
)I D
(A
)
VG (V)
Nonvolatile change in resistance at “room temperature”
EDLT consisting of compressively strained CaMnO3 film
New approach for Mott transistorS
hee
t Res
ista
nce
Temperature
·CMR-manganite, High TC cuprate·1014~ 1015/cm2 carriers
non-doped(VG = 0)carrier doped(VG ≠ 0)
She
et R
esis
tanc
e(lo
garit
hmic
sca
le)
Temperature
“sharp” and “large” resistance change
(Nd,Sm)NiO3 TMI = 200–400 K VO2 TMI = 300–340 K
TMI
NdNiO3 EDLT
S. Asamuna, AS et al., Appl. Phys. Lett. 97, 142110 (2010) R. Scherwitzl et al., Adv. Mater. 22, 5517 (2010).
Nd0.5Sm0.5NiO3 EDLT
NSNO(0.5)/NdGaO3 (110) (Thickness:~6 nm)
10-2
10-3
10-4
Resistivity(Wcm
)
320300240220Temperature (K)
260 280
0V-2.3V-2.5V
(Nd,Sm)NiO3 channelVG
27-33 -13 7Temperature (ºC)
Large resistance change (~105) at room temperatureS. Asamuna, AS et al., unpublished
10-5
10-7
10-8
10-9
10-10
10-11
10-12
10-6
I SD (
A)
3-3 0 1 2-2 -1VG(V)
@300 K
¥
Nonvolatile
insulator
metal
Gate voltage
VO2
VO2 EDLT
Nakano et al., Nature 487, 459 (2012)
Oxide FET
Mott FET
SrTiO3
TiO2 (anatase)
In-Ga-Zn-O
GdBa2Cu3O7
(La,Sr)MnO3
Operation temperature
On/Off ratio Gate material
SrTiO3
References
R. T.
~105 0.37 a-LaAlO3/MgO
R. T.
R. T.
Gate voltage(V)
Mobility(cm2/Vs)
5 APL92, 132107 (2008)
~102.5~105 a-CaHfO3JJAP46, L515 (2007)
La2CuO4 R. T.(?) <10 <8 SrTiO3 APL76, 3632 (2000)
(La,Ca)MnO3
SrRu1-xTixO377KR. T.
<10<1
±10 PZT APL82, 4770 (2003)
superconductivity: TC ~0.3K at VG=-3V electrolyte Nat. Mater. 7, 855 (2008)
100-200K <10 ±3 PRL102, 136402 (2009)
PZT(ferroelectrics )50-300K <3 ±3 Science 284, 1152 (1999)
10-300K <3 ±1 PZT PRB74, 174406 (2006)
~108 12 5 - 6 a-Y2O3APL89, 112123 (2006)
Channel
KTaO3 ~104 0.4 a-Al2O3R. T. 100 APL84, 3726 (2004)
CaMnO3
50KR. T.
>103
~10±2 Adv. Mater. 23, 5822 (2011)
(Nd,Sm)NiO3
~100K >10 ±2.5 Ionic liquid APL97,142110 (2010)
Ionic liquid
Ionic liquid
NdNiO3
±2.5 Ionic liquid unpublished
VO2 260K ~103
R. T. ~105
Ionic liquid±3 Nature 487, 459 (2012)
Feature/potential of Mott FET
• Functionality: electronic, magnetic, and optical switches• Scaling limit: < 10 nm• Nonvolatile and fast switching
Bottleneck/challenge
A large number of carriers (>1014 cm-2 ) is necessary to be doped in order to induce the Mott transition
Summary
For the realization of a practical Mott transistor• (“solid”) Higk-k gate materials with a large breakdown
strength
expected from theoretical and experimental studies on correlated electron materials