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Transcript of Sangwoo Final
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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)