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Y. Tomioka, unpublished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