Electric Field Control of 2D Materials

Yoshi Iwasa

Univ Tokyo & RIKEN

IMPACT 2016 August 23-September 2, 2016Cargèse, Corsica, France

Acknowledgements

AP, Univ Tokyo

Y. Saito,W. ShiF. QinM. YoshidaY. Nakagawa,J. T. Ye→GroningenY. Kasahara→KyotoM. Nakano

IMR, Tohoku Univ

T. Nojima

RIKEN CEMSD. HashizumeT. KikitsuD. Inoue

Reshef Tenne

Alla Zak

Theoretical supportRIKEN CEMS & U Tokyo

N. NagaosaM. EzawaS. HoshinoR. Wakatsuki

Electric field effects in 2D materials

3

100 ~ 101 nm100 ~ 101 mm

Longitudinal electric field Transverse electric field

E ~ 104 MV/cm

J = 1 ~ 100 MA/cm2. E ~ 107 MV/cm

e.g. Current switching

in 1T-TaS2.

R(k

W)

V (V)

M. Yoshida et al. Sci. Adv. (2015).

A. W. Tsen et al. PNAS (2015).

I. Vaskivskyi et al. Nat. Commun. (2016).

J. T. Ye et al. Nat. Mater. (2010).

K. S. Novoselov et al. Science (2004).

B. Radisavljevic et al. Nat. Nanotech. (2011).

Gate-induced superconductivity

Monolayer transistor

e.g.

Small volume!

substrate substrate

E E

Field effect transistor Nonlinear transport

OUTLINE

(1) Transverse electric field effect

1-1 Electric double layer transistor (EDLT)

1-2 A new aspect as a 2D superconductor

1-3 Superconductivity in inorganic nanotubes

(2) Longitudinal electric field effect

2-1 Thinning effect in 1T-TaS2

2-2 Nonvolatile current switching

Basic Ideas

Helmholtz’s electric double layer (1853)

--+

-++-

+

Ele

ctr

osta

tic P

ote

ntia

l

+ --

+ --

+

+

-

-

-

-

+

+

+

+

EDL（ ~1 nm ） Hermann von Helmholtz

(1821-1894)

Electric Double Layer (EDL)

at interfaces between electronic and ionic conductors

Electrochemical cell

Pt Pt

Electric Double Layer

electrochemical interface

similar to solid heterointerface

High electric field x 100

high density charge x 100

EDLC (super capacitor)

Versatile

n2D (cm–2)

107 109 1011 1013 1015105

Semiconductor MetalElectronic phase transition

FET Electric Double Layer Transistor (EDLT)

Insulator

From FET to EDLT (Electric Double Layer Transistor)

Ge J. Bardeen, Nobel Lecture (1956)

ISFET P. Bergveld: IEEE Trans. Biomed. Eng. BM17, 70 (1970).

Si A. Tardella, and J.-N. Chazalviel: Phys. Rev. B 32, 2439 (1985).

H. S. White, G. P. Kittlesen , M. S. Wrighton: J. Am. Chem. Soc. 106, 5375 (1984).

Y. Harima, T. Eguchi, K. Yamashita: Synth. Met. 95, 69 (1998).

M. Krüger, M. R. Buitelaar, T. Nussbaumer, C. Schönenberger, and L. Forró: Appl.

Phys. Lett. 78, 1291 (2001).

S. Rosenblatt, Y. Yaish, J. Park, J. Gore, V. Sazonova, and P. L. McEuen: Nano Lett.

2, 869(2002).

M. Taniguchi and T. Kawai, Appl. Phys. Lett. 85, 3298 (2004).

H. Shimotani, G. Diguet, Y. Iwasa: Appl. Phys. Lett. 86, 022104 (2005).

M. J. Panzer, C. R. Newman, and C. D. Frisbie: Appl. Phys. Lett. 86, 103503 (2005).

D. Nilsson and M. Berggren, Adv. Mater. 17, 353 (2005).

Conducting polymers

Carbon nanotube transistors

Organic transistors

Early works on Ge and Si

History of semiconductor-electrolyte interfaces

M. Krüger et al., APL (2001)

Carbon nanotube EDLTs

S. Rosenblatt, Nano Lett. (2002).

Single-walledMulti-walled

Characteristics of ZnO-EDLT

10

n-type transistor operation

20

15

10

5

0

2

0

I D (

mA

)Le

ak c

urr

ent

(mA

)

0 0.8 1.6 2.4 3.2Gate voltage (V)

VDS = 0.1 V

Transfer curve

0 0.2 0.4 0.6 0.8 1

120

80

40

0

Drain voltage (V)

I D(m

A)

VG

(V)3.1

3.0

2.9

2.8

2.7

2.6

Output curve

H. Shimotani et al., Appl. Phys. Lett. 91, 082106 (2007).

Hall effect measurement of EDL

0.8

0.6

0.4

0.2

0

5

4

3

2

1

0

Sheet

conducta

nce (

mS

)

Carr

ier

den

sity (

10

13

cm

–2)

0 0.5 1 1.5 2 2.5 3

Gate voltage (V)

ne = Q = CV

Solvent moleculeIon

- - -

+ + +

C ~ 7.8 mF/cm2

EDL

ZnO

5–5 0

VH/I

D(k

W) 2

1

0

–1

–2

B (T)

0

1.423

VG(V)

thickness of EDL ~ 1 nm

(cf. 15 nF/cm2 for SiO2)

(e = 10 e0 for PEO solvent)

H. Shimotani et al., Appl. Phys. Lett. 91, 082106 (2007).

Insulator-metal transitions in oxide semiconductors

H. Shimotani et al., Appl. Phys. Lett. (2007). R. Misra et al., Appl. Phys. Lett. (2007).

ZnO InOx

Electric field induced superconductivity in SrTiO3

2.5V

3.5V

2.25V

VG = 2V

2.75V

3V

T ( K )

R (

W/

)

SrTiO3

h / e2

100 300200102

0

106

104

Insulator

Metal

K. Ueno et al. Nater Materials (2008).

STO, YBCO: Goldman et al., PRL (2011)LSCO: Bozovic et al., Nature (2011)MoS2: Takagi et al APL (2012)WS2: Morpurgo et al., Nano Lett (2015)PCCO: Ariando, PRB (2014)

ElectrochemicalTaS2: Y. Yu et al., Nat Nano (2015)MoSe2, MoTe2: W. Shi et al. Sci Rep (2015)FeSe: J. Shiogai et al., Nat Phys (2016)

Superconductivity induced by EDLT

Gate induced ferromagnetism

Y. Yamada et al.,

Science, 2011.

S. Shimizu et al.,

PRL, 2013.

CoxTi1-xO2 Pt Co

K. Shimamura et al.,

APL, 2012.

Electric-field induced phase transitions in correlated electron systems

M-I transitions

M. Nakano et al.,

Nature, 2012.

Metal

Insulator

M-COO transitions

T. Hatano, et al.,

Sci. Rep., 2013.

Metal

Insulator

CDW transitions

M. Yoshida, et al.,

Sci. Rep., 2014.

TaS2

Band bending

Conventional

semiconductor

Strongly correlated

system

Band reconstruction

Bulk

EF

Surface

Fundamental question of correlated FETs

EF

Bulk Surface

How

connected ?OR

Ionic conductors as a gate dielectric

8

6

4

2

0C

arri

er d

ensi

ty [

10

14

cm2]

SiO2 Polymer electro-lyte

Ionic liquid

Ionic liquid (low T)

H. T. Yuan et al., Adv. Funct. Mater. 19, 1046 (2009)

N+

CH3

O CH3

CH3

CH3

S

N-

S

O O OO

F F

F

F

F

F

Ionic liquids

Ion gels

DEME TFSI

BF4

ZnO

Polymer electrolytes

KClO4 + (PEO or PEG)

Ionic liquid + block copolymer

Emerging 2D superconductors

MBE-grown CVD-grown mechanically-exfoliated Interface, field effect

Pb-single layer (1L)Science 324, 1314 (2009).Nature Phys. 6, 104 (2014).

In-1L

PRL 107, 207001 (2011).

FeSe-1L

CPL 29, 03742 (2012).

Ga-2L

PRL, 114, 107003 (2015).Science, aaa7154 (2015).

Tl-Pb-1L

PRL 115, 147003 (2015).

BSCCO-1L

Nature Comm. 5, 5708 (2014).

NbSe2-1～2L

Nature Nano. 10, 765 (2015).Nature Phys: 12, 92 (2016).Nature Phys: 12, 139 (2016).Nature Phys: 12, 208 (2016).

ZrNCl-quasi-1L

Nature Mat. 9, 1314 (2010).Science 350, 409 (2015).

Mo2C-1～2L

Nature Mat. 14, 1135 (2015)

MoS2-quasi-1L

Science 338, 1193 (2012).Science 350, 1352 (2015).Nature Phys: 12, 144 (2016).

WS2, MoSe2 etc.

Sci. Rep. 5, 12534 (2015)Nano Lett. 15, 1197 (2015).

LAO/STO

Science 317, 1196 (2007).Nature 456, 624 (2008).

TiSe2

Nature 529, 185 (2016)

History of 2D superconductors

Physics of 2D superconductors

ZrNCl-EDLT MoS2-EDLT

Y. Saito et al. Science 350, 409 (2015).

Y. Saito et al., Nature Physics, 12, 144 (2016)J. M. Lu et al., Science 350 1353 (2015)

Enhanced Hc2 by spin-orbit interaction and symmetry breaking

Quantum metallic states

Gate Induced Superconductivity in ZrNCl

R-T Curve Insulator

Ionic liquid

Gate Superconductor

Source

Drain

5 mm

ZrNCl nano device

ZrNCl-EDLT:

Y. Saito et al. Science 350, 409 (2015).

R-T Curves for H and H// (ZrNCl)

Y. Saito et al. Science 350, 409 (2015).

Anisotropy in Hc2 (ZrNCl)

2/10//20

2

020

)/1()0(2

12)(

)/1()0(2

)(

c

scGL

c

c

GL

c

TTd

TH

TTTH

m

m

dSC 1.8 nm

GL(0) 13.1nm

Temperature dependence of Hc2

2D GL model

H

H

ZrNCl 1layer ~ 1 nm

Charge accumulation = monolayer1st principle calculation T. Brumme et al. PRB (2014)

Bulk-LixZrNCl

ZrNCl-EDLT

Amplitudefluctuation

Phase fluctuation

Aslamazov-Larkin

Maki-Thompson

+

BKT transition

Aslamazov-Larkin

Maki-Thompson

+

Superconducting fluctuation near Tc in ZrNCl

Φ = 𝚽𝟎 exp 𝑖𝝓Macroscopic wave function

Tc0

TBKT

Phase FluctuationBKT transition

Amplitude FluctuationAZ+MT analysis

e-

e-

e-

e-e-

e-

e-

e-

Interface (2D) vs bulk (3D) : R(H) -T curve

ZrNCl-EDLT (2D) LixZrNCl (3D Anisotropic)

ZrNCl

2DEGE

LixZrNCl

dsc ~ 1.8 nm

60 nm

Flattening resistance at low temperature

H

Quantum metals in highly-crystalline 2D SCs

ZrNCl-EDLT

Y. Saito et al. Science 350, 409 (2015).

Quantum metal induced by vortex fluctuation due to weak pinning

H

Quantum metals in highly-crystalline 2D SCs

ZrNCl-EDLT

Y. Saito et al. Science 350, 409 (2015).

Quantum metal induced by vortex fluctuation due to weak pinning

H

Cu0.03TaS2 (Zhu et al., J. Phys. Cond. Mater 22, 505704 (2010)

Quantum metals in highly-crystalline 2D SCs

ZrNCl-EDLT

Quantum metal induced by vortex fluctuation due to weak pinning

Hh-BN capped bilayer NbSe2

A. W. Tsen et al. Nature Phys. 12, 208 (2016).

Bose metal

Y. Saito et al. Science 350, 409 (2015).

Quantum metals in highly-crystalline 2D SCs

ZrNCl-EDLT

Quantum metal induced by vortex fluctuation due to weak pinning

HSrTiO3-EDLT

Y. Saito et al. Science 350, 409 (2015).

TBKT

Robust zero-resistance in In monolayer

M. Yamada, T. Hirahara and S. Hasegawa, Phys. Rev. Lett. 110 237001 (2013).

No significant broadening in the MBE grown In monolayermaybe due to the grain boundaries

Gate-induced superconductivity in MoX2

(IL)(IL)(KClO4/PEG)

1.0

0.8

0.6

0.4

0.2

0

Re

sis

tan

ce

(a

rb.u

nit

s)

14121086420

Temperature (K)

MoSe2 MoS2MoTe2

W. Shi et al. Sci Rep 5, 12534 (2015)

Superconductivity in WS2

33

Superconductivity in WS2

IDS – VG Curves R – T Curves (log plot)

o Reversible gate control of intercalation

(potassium -doped)Tc = 8.6 K

10-2

10-1

100

101

102

Rs (

W)

12 3 4 5 6

102 3 4 5 6

1002

T (K)

VG = 6 V

2.0

1.5

1.0

0.5

0.0

Rs (

W)

12840

T (K)

VG = 10 V

0 T

2 T

IntercalationEDLTelectrostatic electrochemical

Cf) S. Jo et al., Nano Lett. 15 1197 (2015)

W. Shi et al. Sci Rep 5, 12534 (2015)

2. Longitudinal electric field effect

34/26

Nonvolatile and Memristive switching

in TaS2

M. YoshidaPII-12Next week

1T-TaS2: Electronic phase transition system

1T-TaS2 : Charge density wave (CDW) system

Ta

S

10-4

10-3

10-2

10-1

3D (

W c

m)

3002001000T (K)

C

NC

IC

S

Ta

C NC IC

High TLow T

Commensurate

Nearly-commensurate

In-commensurate

Thickness dependent phase transitions

102

103

104

105

Rs (

W)

3002001000T (K)

100 nm10

2

103

104

105

Rs (

W)

3002001000T (K)

61 nm

102

103

104

105

Rs (

W)

3002001000T (K)

102

103

104

105

Rs (

W)

3002001000T (K)

42 nm

102

103

104

105

Rs (

W)

3002001000T (K)

3002001000T (K)

3002001000T (K)

3002001000T (K)

3002001000T (K)

3002001000T (K)

3002001000T (K)

3002001000T (K)

3002001000T (K)

3002001000T (K)

3002001000T (K)

200

150

100

50

0

TC (

K)

101 2 4 6 8

102

Thickness (nm)Bulk

NC

C

C

NC

IC

NC

IC

1 K/min

Abrupt suppression of NC-C transition on cooling. → Consider kinetics.

Rs(W

)

M. Yoshida et al.,

Sci. Rep. 4, 7302 (2014).

36

104

105

106

3D (

W c

m)

3002001000

T (K)

104

105

106

3D (

W c

m)

3002001000

T (K)

104

105

106

3D (

W c

m)

3002001000

T (K)

104

105

106

3D (

W c

m)

3002001000

T (K)

10-3

10-2

10-1

3D (

W c

m)

3002001000

T (K)

10-3

10-2

10-1

3D (

W c

m)

3002001000

T (K)

10-3

10-2

10-1

3D (

W c

m)

3002001000

T (K)

10-3

10-2

10-1

3D (

W c

m)

3002001000

T (K)

10-3

10-2

10-1

3D (

W c

m)

3002001000

T (K)

10-3

10-2

10-1

3D (

W c

m)

3002001000

T (K)

10-3

10-2

10-1

3D (

W c

m)

3002001000

T (K)

10-3

10-2

10-1

3D (

W c

m)

3002001000

T (K)

10-3

10-2

10-1

3D (

W c

m)

3002001000

T (K)

10-3

10-2

10-1

3D (

W c

m)

3002001000

T (K)

10-3

10-2

10-1

3D (

W c

m)

3002001000

T (K)

10-3

10-2

10-1

3D (

W c

m)

3002001000

T (K)

Cooling-rate-dependent phase transition

1 K/min

0.2 K/min

8 K/min

1 K/min

10 K/min

5 K/min

1 K/min

10 K/min

Thickness = 31 nm 61 nm Bulk

C

NC

IC

C

NC

IC

C

NC

IC

Super-Cooled

NC

37

Phase diagram considering kinetics

10-2

10-1

100

101

QC (

K/m

in)

9

102 3 4 5 6 7 8 9

100Thickness (nm)

200

150

100

50

0

TC (

K)

10-2

10-1

100

101

QC (

K/m

in)

9

102 3 4 5 6 7 8 9

100Thickness (nm)

200

150

100

50

0

TC (

K)

10-2

10-1

100

101

QC (

K/m

in)

9

102 3 4 5 6 7 8 9

100Thickness (nm)

200

150

100

50

0

TC (

K)

10-2

10-1

100

101

QC (

K/m

in)

9

102 3 4 5 6 7 8 9

100Thickness (nm)

200

150

100

50

0

TC (

K)

Bulk

NC-CDW

C-CDW

The ordering kinetics of the transition becomes slow by thinning.

C-CDW

NC-CDWCritical cooling rate

for the occurrence

of the transition

Rc (K/min)

M. Yoshida et al., Sci. Adv. 1, e1500606 (2015).

103

104

3002001000T (K)

103

104

3002001000T (K)

Nonvolatile switching from the NC state by Vin-plane

Thickness = 19 nm

1 K/min

225 K

Rs

(Ω)

IC

NC

NC

IC

Vin-plane

M. Yoshida et al., Sci. Adv. 1, e1500606 (2015).A. W. Tsen et al. PNAS (2015).

I. Vaskivskyi et al. Nat. Commun. (2016).

103

104

3002001000T (K)

103

104

3002001000T (K)

Multiple metastable state by Vin-plane

103

104

3002001000T (K)

Apply Vin-plane

at T = 165 K

300 K

285 K

260 K

195 K

225 K

Rs

(Ω)

IC

NC

40

Thickness = 19 nm

1 K/minIC

NC Vin-plane

M. Yoshida et al., Sci. Adv. 1, e1500606 (2015).

2

1

40030020010005

04003002001000

Rs

(kW

)V

(V)

Time (s)

1.0

0.5x1

03

20010005

02001000

Rs

(kW

)V

(V)

Time (s)

Apply V at T = 90 K

tw = 200 s

tw = 100 ms

Switching to various electronic states

Memristive switing

C

NC

IC

41

Thickness

= 36 nm

The stability of the voltage-induced metastable states

42

Thickness = 19 nm

1 K/min

Apply Vin-plane

at T = 165 K

300 K

285 K

260 K

225 K

195 K

Thickness = 74 nm

1 K/min

Apply Vin-plane

at T = 225 K

The metastable states can also exist in thick crystals, but are fragile.

IC

NC

IC

NC

C

Energy landscapes

C NC

Energ

yE

nerg

y

Bulk

Thin flake

Summary

(1) 2D superconductivity by EDLT

(2) Quantum metallic states under magnetic fields in ZrNCl

(3) Superconductivity in WS2 nanotube/

transport reflecting tublar and chiral structure

New states of matter in 2D materials created by electric fields

Transverse electric field: E ~ 107 V/cm

(1) Many metastable states, possibly semimetallic in TaS2

(2) Non-volatile memristive switching

Longitudinal electric field: E ~ 104 V/cm