Coherent Transport and Resonant Coupling Coherent Transport and Resonant Coupling in Molecule Transistorsin Molecule Transistors
Coherent Transport and Resonant Coupling Coherent Transport and Resonant Coupling in Molecule Transistorsin Molecule Transistors
HyunwookHyunwook SongSong1,21,2, , TakheeTakhee LeeLee11
11Gwangju Institute of Science and Technology, and Gwangju Institute of Science and Technology, and 22Yale UniversityYale UniversityHyunwookHyunwook SongSong1,21,2, , TakheeTakhee LeeLee11
11Gwangju Institute of Science and Technology, and Gwangju Institute of Science and Technology, and 22Yale UniversityYale University
Mark Reed, Yale University Mark Reed, Yale University Mark Reed, Yale University Mark Reed, Yale University
NGC2011 Moscow, Russian Federation September 14, 2011 NGC2011 Moscow, Russian Federation September 14, 2011 M. M. Reed (Yale) Reed (Yale)
Challenge:Challenge:Challenge:Challenge:gga transistor where the molecular orbital structure is modulateda transistor where the molecular orbital structure is modulated
Fabrication & design challengesFabrication & design challenges
gga transistor where the molecular orbital structure is modulateda transistor where the molecular orbital structure is modulated
Fabrication & design challengesFabrication & design challengesFabrication & design challengesFabrication & design challenges Molecular identification in the junctionMolecular identification in the junction Orbital level modulation, contact/molecular orbital coupling?Orbital level modulation, contact/molecular orbital coupling?
C h t t li ?C h t t li ?
Fabrication & design challengesFabrication & design challenges Molecular identification in the junctionMolecular identification in the junction Orbital level modulation, contact/molecular orbital coupling?Orbital level modulation, contact/molecular orbital coupling?
C h t t li ?C h t t li ?
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Coherent tunneling?Coherent tunneling? Coherent tunneling?Coherent tunneling?
Spectroscopic methods (control: Spectroscopic methods (control: alkanealkane SAMs)SAMs)Spectroscopic methods (control: Spectroscopic methods (control: alkanealkane SAMs)SAMs)
L h d d i hL h d d i h lklkL h d d i hL h d d i h lklk Length dependence with Length dependence with alkanesalkanes
T independent tunnelingT independent tunneling
Length dependence with Length dependence with alkanesalkanes
T independent tunnelingT independent tunnelingp gp g
IETSIETS
p gp g
IETSIETS
10
100
I(V,T)
(80-300K) 10-2
100
10-91.0V0.9V0.8V0.7V0 6V
C8 = 0.79 Å-1
1
10
I (nA
)
C12
(80 300K)
10-6
10-4
0.4V
Jd2 (A
)
Jd (A
/cm
)10-13
10-11
0.6V0.5V
C12
-1.0 -0.5 0.0 0.5 1.0
0.1
V (V)
C12
12 14 16 18 20 22 2410-8
100.3V0.2V0.1V
Length (Å)
10-15
C12C16
NGC2011 Moscow, Russian Federation September 14, 2011 NGC2011 Moscow, Russian Federation September 14, 2011 M. M. Reed (Yale) Reed (Yale)
W. Wang W. Wang et alet al, PRB 68, 035416 (2003); also see H.B. , PRB 68, 035416 (2003); also see H.B. AkkermanAkkerman et alet al, , NatureNature 441441, 69 (2006) , 69 (2006)
Inelastic Electron Tunneling Spectroscopy (IETS)Inelastic Electron Tunneling Spectroscopy (IETS)Tunneling electrons couple withTunneling electrons couple with vibrationalvibrational modes of moleculemodes of moleculeTunneling electrons couple with Tunneling electrons couple with vibrationalvibrational modes of moleculemodes of molecule
Elastic tunnelingElastic tunnelingeVeV < < hh
hh
II
-- hh
hhVV
I l ti t liI l ti t li
G = dI/dVG = dI/dV
ee
Inelastic tunnelingInelastic tunnelingeVeV > > hh
== ee ++ ieie
-- hh hhVV
ee ieie
-- hh
dG/dV = ddG/dV = d22I/dVI/dV22
VV
ee
ieie
NGC2011 Moscow, Russian Federation September 14, 2011 NGC2011 Moscow, Russian Federation September 14, 2011 M. M. Reed (Yale) Reed (Yale)
hhVV
IETS on SAMsIETS on SAMs
20 0µ
0 1000 2000 3000 4000 cm-1Au-S stretching (33 meV) C-C stretching (133 meV) SAu
15.0µ
20.0µ
V2 ) CH2 wagging (158 meV)
S-C stretching (80 meV)
S
5.0µ
10.0µ
2 I/dV
2 (A/V Au
SiO-HS-H
H H
SAu
-5.0µ
0.0d2
CH2 stretching (357 meV)CH2 rocking (107 meV) CH2 scissoring (186 meV)
Si-H
Scissoring RockingC C
0.0 0.1 0.2 0.3 0.4 0.5V (V)
( )
WaggingStretching
CC2 @ T = 4 K
NGC2011 Moscow, Russian Federation September 14, 2011 NGC2011 Moscow, Russian Federation September 14, 2011 M. M. Reed (Yale) Reed (Yale)
gg gStretching
Wang Wang et. al,et. al, NanoLettersNanoLetters 44, 643 (2004), 643 (2004)
Molecular transistorsMolecular transistorsMolecular transistorsMolecular transistors
LUMOLUMO
EEFF
HOMOHOMOSource Drain
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FabricationFabricationFabricationFabrication
Drain
Source(Au)
Drain(Au)
Gate (Al2O3/Al)
•• electromigratedelectromigrated break junction technique break junction technique gg j qj qin a vacuum at 4.2 K, leads in a vacuum at 4.2 K, leads precoatedprecoated•• underlying Alunderlying Al22OO33/Al gate /Al gate •• >5K devices, ~50% open, ~30% CB & >5K devices, ~50% open, ~30% CB & other 10% asymmetric 10% operationalother 10% asymmetric 10% operationalother, ~10% asymmetric, ~10% operational,other, ~10% asymmetric, ~10% operational,~ 10% of those show significant gating~ 10% of those show significant gating Courtesy Dan Ralph (Cornell)Courtesy Dan Ralph (Cornell)
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Single Molecule JunctionsSingle Molecule Junctions
ODT (n=8), BDTODT (n=8), BDT
Single Molecule JunctionsSingle Molecule Junctions
ODT (n=8), BDTODT (n=8), BDTAu
Au
10 nm
( ),( ),consistent single molecule Gconsistent single molecule G
( ),( ),consistent single molecule Gconsistent single molecule G 1 µm
Low bias (0Low bias (0--0.1V) conductance0.1V) conductanceLow bias (0Low bias (0--0.1V) conductance0.1V) conductanceNGC2011 Moscow, Russian Federation September 14, 2011 NGC2011 Moscow, Russian Federation September 14, 2011 M. M. Reed (Yale) Reed (Yale)
Single molecule junctions Single molecule junctions Single molecule junctions Single molecule junctions 0 85 Å 1
G ∝ exp(-d)g jg j
Length dependence with Length dependence with alkanesalkanes
g jg j
Length dependence with Length dependence with alkanesalkanes
= 0.85 Å-1
T independent tunnelingT independent tunneling T independent tunnelingT independent tunneling
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Transition Voltage Spectroscopy (TVS)Transition Voltage Spectroscopy (TVS)Transition Voltage Spectroscopy (TVS)Transition Voltage Spectroscopy (TVS)
mdVI B )2(4exp
2/132
In high bias (FN tunneling),
eVVI
3exp
rewriting, dI 1)2(4 2/13
Vemd
VI B 1
3)2(4ln
2/13
2
In low bias (direct tunneling),
2/1
2)2(21lnln Bmd
VVI
J.M. Beebe J.M. Beebe et alet al, , Phys. Rev. Phys. Rev. LettLett. . 9797, 026801 (2006), 026801 (2006)
also Beebe, also Beebe, ACS ACS NanoNano 22, 827 (2008); Roth, , 827 (2008); Roth, Appl. Phys. Appl. Phys. LettLett. . 9292, 042107 (2008); Wang, , 042107 (2008); Wang, JACSJACS 131131, , 5980 (2009);5980 (2009); FrisbieFrisbie ScienceScience 320320 1482 (2008);1482 (2008); YuYu J Phys :J Phys : CondensCondens MatterMatter 2020 374114 (2008);374114 (2008);5980 (2009); 5980 (2009); FrisbieFrisbie, , ScienceScience 320320, 1482 (2008); , 1482 (2008); Yu, Yu, J. Phys.: J. Phys.: CondensCondens. Matter . Matter 2020, 374114 (2008); , 374114 (2008); Liu, Liu, ACS NanoACS Nano 22, 2315 (2008); ......, 2315 (2008); ......
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TVS: Barrier (FN) Tunneling versus Coherent Transport TVS: Barrier (FN) Tunneling versus Coherent Transport TVS: Barrier (FN) Tunneling versus Coherent Transport TVS: Barrier (FN) Tunneling versus Coherent Transport
for HOMO transport
B
for HOMO transport
The coherent “resonant tail” picture surprisingly gives very similar “FNThe coherent “resonant tail” picture surprisingly gives very similar “FN--type” type” b h i (Mb h i (M A id iA id i d Md M T k dT k d Ph RPh R B 81B 81 235114 (2010) J Ch t235114 (2010) J Ch tbehavior (M. behavior (M. AraidaiAraidai and M. and M. TsukadaTsukada, , Phys Rev. Phys Rev. B 81B 81, 235114 (2010); J. Chen et , 235114 (2010); J. Chen et al, al, Phys. Rev. Phys. Rev. B 82B 82, 121412 (2010)), 121412 (2010))
Orbital energies may be different by ~10% (Orbital energies may be different by ~10% (II BaldeaBaldea ChemChem PhysPhys 377377 15 (2010))15 (2010))Orbital energies may be different by ~10% (Orbital energies may be different by ~10% (I. I. BaldeaBaldea, , ChemChem PhysPhys. . 377377, 15 (2010)), 15 (2010))
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TVS: Barrier Tunneling TVS: Barrier Tunneling versus Coherent Transport versus Coherent Transport TVS: Barrier Tunneling TVS: Barrier Tunneling versus Coherent Transport versus Coherent Transport
Coherent model predicts length independent TVS Coherent model predicts length independent TVS VVtranstrans , contradicts FN model , contradicts FN model
pppp
Vtrans = 1.86 V
((HuismanHuisman et alet al, , NanoNano LettLett. . 99, 3909 (2009)), 3909 (2009))
H. Song et al. J. Phys. Chem. C 114, 20431 (2010)
-18
-16
C8C9
C10
Vtrans 1.86 V
2 0
2.4
DC8DC9
DC10DC11 DC12
g y , ( )
22
-20
ln(I/
V2 )
5
C10
C11
C121.6
2.0
Vtra
ns (V
)
DC8 DC10
-24
-22
-2 0 2-5
0
I (nA
)
V (V)
C8
8 9 10 11 121.2
N b f C b0 10 20 301/V (V-1)
Number of Carbon
NGC2011 Moscow, Russian Federation September 14, 2011 NGC2011 Moscow, Russian Federation September 14, 2011 M. M. Reed (Yale) Reed (Yale)
Transistor transfer characteristics, ODTTransistor transfer characteristics, ODTTransistor transfer characteristics, ODTTransistor transfer characteristics, ODT
Al2O3/Al
15-8
High V Low V
a b
AuAu
S D5
10
-12
-10 VG = -3.3 V
VG = -2.8 V
VG = -2 6 VS DG
0 I (nA
)
VG = -2.8 VVG = -3.3 V
-16
-14
ln(I/
V2 ) VG = -2.6 V
VG = -2.1 V
VG = -1.6 V
-10
-5
VG = -1.1 VVG = -1.6 VVG = -2.1 VVG = -2.6 V
G
-20
-18VG = -1.1 V
VG = 0.0 V
-2 -1 0 1 2-15
V (V)
VG = 0.0 V
0 10 20 30-22
1/V (V-1)d
H. Song H. Song et alet al, , NatureNature 462462, 1039 (2009), 1039 (2009)H. Song H. Song et alet al, , NatureNature 462462, 1039 (2009), 1039 (2009)
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Gate dependence of Gate dependence of VVtranstrans, ODT, ODTGate dependence of Gate dependence of VVtranstrans, ODT, ODT
1.7 1.6
D DFN
( )c d
B D BDeV EF
1.4
1.5
1.6
ans (e
V)
1.4
1.5
V (e
V) S
DeV
S
DeV
DVDV
FN
V / VA C
HOMOeVG,eff
Source DrainB
1.1
1.2
1.3eVtra
1.2
1.3
eV
SDeV
SDeV
DT
eVtrans/VG = +0.25 eV/V
dln(I/V2)/d(1/V)C A
-3.2 -2.8 -2.4 -2.0 -1.6 -1.2VG (V)
-0.8 -0.6 -0.4 -0.2eVG,eff (eV)
-0.30.25
VVtranstrans scales linearly and reversibly with scales linearly and reversibly with VVGG
Positive Positive for pfor p--type (HOMO); Negative type (HOMO); Negative for nfor n--type (LUMO)type (LUMO)
VVtrans,0trans,0 = 1.93 V for ODT, which approximates= 1.93 V for ODT, which approximates EEFFEEHOMOHOMO at zero gateat zero gate
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Gate lever arm Gate lever arm –– screening is dominantscreening is dominant
S.S. S.S. DattaDatta et al, Phys Rev. B79, 205404 (2009)et al, Phys Rev. B79, 205404 (2009)S.S. S.S. DattaDatta et al, Phys Rev. B79, 205404 (2009)et al, Phys Rev. B79, 205404 (2009)NGC2011 Moscow, Russian Federation September 14, 2011 NGC2011 Moscow, Russian Federation September 14, 2011 M. M. Reed (Yale) Reed (Yale)
Transistor transfer characteristics, BDTTransistor transfer characteristics, BDTTransistor transfer characteristics, BDTTransistor transfer characteristics, BDT
cS
D
SD
S Dba
-12
-10
-8
V2 )
High V Low V
VG = -3 V 1.6
2.0
eV) eVtrans/VG
= +0.22 eV/V
) 0 310 232
4
6
VG = 2 VVG = 1 VVG = 0 VVG = -1VVG = -2 VVG = -3 V
-16
-14
12
ln(I/
V2
VG = 3 V0.8
1.2
eVtra
ns (e
0 0 0 00.81.01.21.4
eV (e
V) FN
DTS D
I(µA
) -0.310.23
-4
-2
0
VG = 3 VG
-18
0 5 10 15 20 1/V (V-1)
-3 -2 -1 0 1 2 3
0.4
VG (V)
-0.5 0.0 0.5eVG,eff (eV)G
S D
-1 0 1-6
4
V (V)
H. Song H. Song et alet al, , NatureNature 462462, 1039 (2009), 1039 (2009)H. Song H. Song et alet al, , NatureNature 462462, 1039 (2009), 1039 (2009)
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Complementary transistorsComplementary transistors
SHHS
1 4
1.6 V(V
FN
-0.30.22
-0.3 0.0 0.3 0.61.2
1.4 V)
eVG,eff (eV)
DT
pp--type (HOMO) for BDT (type (HOMO) for BDT ( = +0 22) Au= +0 22) Au--SHSHpp type (HOMO) for BDT (type (HOMO) for BDT ( +0.22), Au +0.22), Au SHSH
nn--type (LUMO) for BDCN (type (LUMO) for BDCN ( = = --0.21), Au0.21), Au--CNCN
Closer to LUMO offset agrees with experiment (Closer to LUMO offset agrees with experiment (BahetiBaheti, , NanoNano LettLett. . 88, , g p (g p ( ,, ,,715 (2008)) and calculation (715 (2008)) and calculation (XueXue, , Phys. Phys. RevRev. . B 69B 69, 085403 (2004))., 085403 (2004)).
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Single Molecule IETSSingle Molecule IETS
II VVAu-ODT-Au Au-BDT-Au
II--VVDCDC
dIdI//dVdV
dd22I/dVI/dV22
H. Song H. Song et alet al, , Appl. Phys. Appl. Phys. LettLett. . 9494, 103110 (2009), 103110 (2009)NGC2011 Moscow, Russian Federation September 14, 2011 NGC2011 Moscow, Russian Federation September 14, 2011 M. M. Reed (Yale) Reed (Yale)
ODTODT IETSODT IETSODT IETSODT IETS
ODT
(C
H2)
(C
-H)
CH
2)
(CH
2)C
-S)
(C-C
)
(A
u-S) (
C
(v(C v
25 50c d
15
20
25
M (m
V)
30
40
50
M (m
V)
c d
(d2 I/d
V2 )/(
dI/d
V)(C-H)
7.8 mV7.2 mV6.1 mV4.9 mV4.3 mV3 8 V 4 2 K
10 K20 K30 K40 K50 K
(C-H)
(d2 I/d
V2 )/(
dI/d
V)
5
10
15
FWH
M
10
20
30
FWH
M
0.34 0.36 0.38(
V (V)
3.8 mV
4.2 K
4.2 K
7.8 mV
0.34 0.36 0.38
(
V (V)
3 4 5 6 7 85
AC modulation (RMS value) (mV)0 10 20 30 40 50
10
Temperature (K)
NGC2011 Moscow, Russian Federation September 14, 2011 NGC2011 Moscow, Russian Federation September 14, 2011 M. M. Reed (Yale) Reed (Yale)
IETS (VIETS (V ) ODT) ODTIETS (VIETS (V ) ODT) ODT
W b ( -1)
IETS (VIETS (VGG), ODT), ODTIETS (VIETS (VGG), ODT), ODT
1.5 0 500 1000 1500 2000 2500 3000 3500
(V-1)
Wavenumbers (cm-1)
0.40.80.37
(d2I/dV2)/(dI/dV)
(C-H)
eVG,eff = -0.75 eVeVG,eff = -0.5 eVeVG,eff = -0.25 eV(
Au-
S)
H)
a b
0.5
1.0
/dV
2 )/(dI
/dV
) (
0.2
0.3
eV (e
V)
(C-C)w(CH2)
s(CH2)
eVG,eff = 0 eV
(C
-S)
r(C
H2)
(C
-C) w(C
H2)
s(C
H2)
(C
- H
0.0 0.1 0.2 0.3 0.40.0
(d2 I/
V (V)0.00 -0.25 -0.50 -0.75
0.0
0.1
eV (eV)
(Au-S)
(C-S)r(CH2)
(C C)
S DG
V (V) eVG,eff (eV)
ODT: no electrodeODT: no electrode--orbital coupling, far from resonant systemorbital coupling, far from resonant systemODT: no electrodeODT: no electrode--orbital coupling, far from resonant systemorbital coupling, far from resonant system
BDT?BDT?BDT?BDT?
NGC2011 Moscow, Russian Federation September 14, 2011 NGC2011 Moscow, Russian Federation September 14, 2011 M. M. Reed (Yale) Reed (Yale)
NearNear--resonant IETSresonant IETS((PerssonPersson && BaratoffBaratoff PRLPRL 5959 339 (1987) & others)339 (1987) & others)NearNear--resonant IETSresonant IETS((PerssonPersson && BaratoffBaratoff PRLPRL 5959 339 (1987) & others)339 (1987) & others)((PerssonPersson & & BaratoffBaratoff, PRL , PRL 5959, 339 (1987), & others), 339 (1987), & others)((PerssonPersson & & BaratoffBaratoff, PRL , PRL 5959, 339 (1987), & others), 339 (1987), & others)
near near eVeV = = for a molecular vibration, for a molecular vibration, the change the change in the total normalized in the total normalized tunneling conductance is (orbital energy Etunneling conductance is (orbital energy EMM , width , width , coupling , coupling E E ););near near eVeV = = for a molecular vibration, for a molecular vibration, the change the change in the total normalized in the total normalized tunneling conductance is (orbital energy Etunneling conductance is (orbital energy EMM , width , width , coupling , coupling E E ););
2 22M F
2 2 2M F M F
M F
( ) ( / 2) ( )( ) ( / 2) ( ) ( / 2)
( )1 ln
E EE eVE E E E
E E eV2 2
M F
lnπ ( ) ( / 2)
E E
Implications:Implications:Implications:Implications:
Far from resonant Far from resonant –– no change in no change in intensity, for either small intensity, for either small linewidthlinewidth or large spacingor large spacing
Far from resonant Far from resonant –– no change in no change in intensity, for either small intensity, for either small linewidthlinewidth or large spacingor large spacingg p gg p g
Near resonant Near resonant –– enhancement in enhancement in intensity, increasingly “intensity, increasingly “FanoFano--
g p gg p g
Near resonant Near resonant –– enhancement in enhancement in intensity, increasingly “intensity, increasingly “FanoFano--type” type” lineshapeslineshapestype” type” lineshapeslineshapes
MiiMii et al, Phys Rev et al, Phys Rev B 68B 68, 205406 (2003)., 205406 (2003).
NGC2011 Moscow, Russian Federation September 14, 2011 NGC2011 Moscow, Russian Federation September 14, 2011 M. M. Reed (Yale) Reed (Yale)
BDT: resonantly enhanced IETSBDT: resonantly enhanced IETSBDT: resonantly enhanced IETSBDT: resonantly enhanced IETS
0 500 1000 1500 2000 2500
3
2
Wavenumbers (cm-1)
0.2
(8a)
a b
S) 8a)
-5.1 16.5
(d2I/dV2)/(dI/dV)
dip
peakS
(d
-1)
2
1
0 0
1
6
0.1
eV (e
V)
(C-H)
(18a)
eVG,eff = 0 eV
(Au
-S
(C
-H) (
1 8
(8a
)
peak
dippeak
dip
peak
HOMOVG,eff
SD
2I/dV2)/(dI/dV
V2 )/(
dI/d
V) (
V- 6
3
0
32
10
-0.35 -0.40 -0.45eVG,eff (eV)
eV = 0 22 eV
HOMOVG,eff
SD
5
(18a)
cPersson & Baratoff V) (V
-1)(d2 I/d
V
40
20
32
1
eVG,eff = -0.22 eV
HOMOVG,eff
SD
4
5
eVG,eff =
FitExperiment
(18a)
(%
)
model
00eVG,eff = -0.66 eV
GS D
3 0.12 0.16
d2 I/dV
2 (a.u
.)
V (V)
0 eV-0.22 eV-0.66 eV
,
0.0 0.1 0.2 0.3V (V)
-0.3 -0.4 -0.5 -0.6eVG,eff (eV)
NGC2011 Moscow, Russian Federation September 14, 2011 NGC2011 Moscow, Russian Federation September 14, 2011 M. M. Reed (Yale) Reed (Yale)
SummarySummarySummarySummary
Molecular transistor with orbital gatingMolecular transistor with orbital gatingg gg g
Coherent transport, resonant couplingCoherent transport, resonant coupling
“n” & “p” type“n” & “p” type
Acknowledgements to J. Chen, Y. H. Jang, H. Acknowledgements to J. Chen, Y. H. Jang, H. JeongJeong, Y. Kim, I. , Y. Kim, I. KretzschmarKretzschmar, , D.R. Lombardi, C. D.R. Lombardi, C. MMüüllerller, D. , D. RoutenbergRoutenberg, , W. Wang, and C. ZhouW. Wang, and C. Zhou
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