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Resistivity Enhancement Due To

Coulomb Drag In Double Layer Graphene

NOV. 30 2011

SANGWOO KANG


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The flow of electrons in the bottom (active) layer will dragelectrons in the top (passive) layer through Coulombinteraction. This will affect the conduction in the activelayer itself.

COULOMB DRAG

bottom (active) layer

inter-layer dielectric

top (passive) layer

bottom gate (BG)

e- e-e-e

-e-

e- e- e- e- e- e-

- V +

current flow


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Need high on/off current ratio for digital logic application Lack of a bandgap makes graphene disadvantageous

GNR& biased BLG?

[1] M. Han et al., Physical Review Letter 98, 206805 (2007)[2] E. V. Castro et al., Physical Review Letter 99, 216802 (2007)

High on/off ratio possible without a finite bandgap

[3] N M RPeres et al., Euro Physics Letter 95, 18001 (2011)

WHAT CAN WE USE THIS FOR?


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RESISTIVITY ENHANCEMENT


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LIMITING CASES


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RELATED EQUATIONS


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EXPERIMENTAL RESULTS

Coulomb drag has been experimentally observed@ tAl2O3 = 8 nm, uT=4200-12000 cm

2/Vs , uB = 4500-22000 cm2/Vs, n0=2.3E11

[6] S. Kim et al., Phys. Rev. B 83, 161401 (2011)


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PROBLEMS?

1010

10 11

1012

1013

1010

1011

1012

10

13

0

1

2

3

4

x 104

Geomet r i c Mean of Vt& Vb

0

0. 5

1

1. 5

2

2. 5

3

3. 5

4x 10

4

1010

10 11

1012

1013

1010

1011

1012

1013

0

1

2

3

4

x 104

Drag Resist iv i ty Vd

0

0. 5

1

1. 5

2

2. 5

3

3. 5

4x 10

4

1010

1011

1012

1013

1010

1011

1012

1013

0

1

2

3

4

x 104

Layer Resist iv i ty Vl

0

0. 5

1

1. 5

2

2. 5

3

3. 5

4x 10

4

1010

1011

1012

1013

1010

1011

1012

1013

0

1

2

3

4

x 104

Independent Layer Resist iv i ty Vb

0

0. 5

1

1. 5

2

2. 5

3

3. 5

4x 10

4

nB nTnB nT

nB nTnB nT

drag resistivity

independent layer resistivityactive layer resistivity

operation rangeofKims device


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PROBLEMS?

Drag resistivity is too low, so the bottom (active) layerresistivity is dominated by the independent layerresistivity

1 01 1

1 01 2

1 01 3

1 01

1 02

1 0

3

1 04

1 05

1 06

Bot tom Layer Carr ier De nsi ty ( nb

)

R

es

istivity

(VL

)

Va

Vd

VL

VB

0 5 1 0 1 5

x 1011

0

0 .5

1

1 .5

2

2 .5

3

3 .5x 10

4

Bo t tom Layer C arrier Densi ty ( nb

)

R

esistivity

(VL

)

Va

Vd

VL

VB

linearscale log scale


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1011

1 012

1013

101

102

103

10

4

105

106

Bottom Layer Carr ier De nsity ( nb

)

Resistivity

(VL

)

Va

Vd

VL

V

B

1 011

1012

1 013

1 01

1 02

1 03

1 0

4

1 05

1 06

Bottom Layer Carr ier De nsity ( nb

)

Resistivity

(VL

)

Va

Vd

VL

V

B

SOLUTIONS?

tAl2O3 = 3 nm n0 = 1E10 cm-2


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1 01 1

1 012

1 013

1 01

1 02

1 0

3

1 04

1 05

1 06

Bo ttom Layer C arrier Density ( nb

)

Res

istivity

(VL

)

Va

Vd

VL

VB

HOW ABOUT ON hBN?

1 01 1

1 01 2

1 01 3

1 01

1 02

1 0

3

1 04

1 05

1 06

Bot tom Layer Carr ier De nsi ty ( nb

)

R

es

istivity

(VL

)

Va

Vd

VL

VB

hBN substrate SiO2 substrate


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SUMMARY

Active layer resistivity can be enhanced by the Coulombdrag in double-layer graphene when drag resistivity issufficiently large

Drag resistivity in Kims device was too low due to

relatively thick inter-layer dielectric, low mobility and highresidual carrier density

In devices with scaled down inter-layer dielectric thickness,on top of an hBN substrate could show such phenomenon


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REFERENCES[1] M. Han et al., Physical Review Letter 98, 206805 (2007)

[2] E. V. Castro et al., Physical Review Letter 99, 216802 (2007)

[3] N M RPeres et al., Euro Physics Letter 95, 18001 (2011)

[4] K. Nomura et al., Phys. Rev. Lett. 98, 076602 (2007)

[5] W.-K. Tse et al., Phys. Rev. B 76, 081401 (2007)

[6] S. Kim et al., Phys. Rev. B 83, 161401 (2011)

[7] C. R. Dean et al., Nature Nanotech. 5, 772 (2010)

[8] L. A. Ponomarenko et al., Nature Physics Letter (2011)

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