evtrans

Molecular Transistors
Mark A. Reed
Depts. of Applied Physics and Electrical Engineering
Yale Institute for Nanoscience & Quantum Engineering
Hyunwook Song
Department of Applied Physics, Kyung Hee University
Takhee Lee
Department of Physics, Seoul National University
with: Youngsang Kim and Heejun
Jeong (Hanyang), Ilona Kretzschmar
(Yale/CCNY), Wenyong Wang
(Yale/Wyoming), Sonya Sawtelle and
Zak Kolbos (Yale)
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Mesoscopics
Reed Lab
Biosensors
Device scaling
Electrokinetic physics
Bioelectronic interfaces
Nanoionic and
& applications
nanofluidic devices
Molecular transport
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Single Molecule Measurements
Cui et. al, Science 294, 571 (2001)
Reed et. al, Science 278, 252 (1997)
Purdue Physics seminar
Reichert et. al,
PRL 88, 176804 (2002),
Proc. Bad Honnef (2003)
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Challenge:
a transistor where the molecular
orbital structure is modulated




Fabrication & design challenges
Molecular identification in the junction
Orbital level modulation
Molecular engineering
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Spectroscopic methods (control: alkane SAMs)
 Length dependence with alkanes
 T independent tunneling
 IETS
100
Jd (A/cm)
I (nA)
10-2
(80-300K)
10
1
C12
-0.5
0.0
0.5
1.0
10-9
10-11
-4
10
10-6
0.1
-1.0
1.0V
0.9V
0.8V
0.7V
0.6V
0.5V
C8 β = 0.79 Å-1
I(V,T)
10-8
12
0.4V
0.3V
0.2V
0.1V
14
10-13
C12
C16
16
18
Jd2 (A)
100
20
22
24
10-15
Length (Å)
V (V)
W. Wang et al, PRB 68, 035416 (2003); also see H.B. Akkerman et al, Nature 441, 69 (2006)
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Inelastic Electron Tunneling Spectroscopy (IETS)
Tunneling electrons couple with vibrational modes of molecule
Elastic tunneling
eV < hν
I
- hν
V
hν
σe
G = dI/dV
Inelastic tunneling
eV > hν
σ = σe + σie
- hν
hν
dG/dV = d2I/dV2
σe
σie
- hν
hν
Purdue Physics seminar
V
West Lafayette, IN
September 18, 2015
V
M. Reed (Yale)
IETS on SAMs
Au
S
Au-S stretching (33 meV) C-C stretching (133 meV)
-1
0
1000
2000
4000 cm
3000
20.0µ
S-C stretching (80 meV)
d2I/dV2 (A/V2)
15.0µ
CH2 wagging (158 meV)
10.0µ
5.0µ
S-H
Si
0.0
-5.0µ
S
Au
CH2 rocking
(107 meV)
0.0
0.1
Au
O-H
H
H
Si-H
CH2 stretching (357 meV)
CH2 scissoring (186 meV)
0.2
0.3
0.4
C
C
Scissoring
Rocking
0.5
V (V)
C
C
2ω @ T = 4 K
Stretching
Wagging
Wang et. al, NanoLetters 4, 643 (2004)
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
temperature & modulation dependencies, non-resonant
0
20
-1
1000 2000 3000 4000 cm
experiment (4K)
Experimental
result
theory (NLSQ)
NLQS
80K
15
10
Wmod=1.7VRMS
5
saturation due to intrinsic linewidth
0
d2I/dV2 (A/V2)
FWHM (mV)
80.0µ
65K
60.0µ
50K
40.0µ
35K
20.0µ
20K
1 2 3 4 5 6 7 8 9 10 11 12
AC modulation (RMS value) (mV)
4.2K
0.0
0.0 0.1 0.2 0.3 0.4 0.5
2
2
2
W = Wmodulation
+ Wthermal
+ Wintrinsic
V (V)
Vrms = 8.7 mV
Wtherm=5.4kBT
W intrinsic, C-C = 3.73 ± 0.98 meV
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Molecular transistor structures
LUMO
EF
Source
Drain
HOMO
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Fabrication
Drain
(Au)
Source
(Au)
Gate
(Al2O3/Al)



electromigrated break junction technique
in a vacuum at 4.2 K, leads precoated
underlying Al2O3/Al gate
>5K devices, ~50% open, ~30% CB &
other, ~10% asymmetric, ~10% operational,
~ 10% of those show significant gating
Purdue Physics seminar
West Lafayette, IN
Courtesy Dan Ralph (Cornell)
September 18, 2015
M. Reed (Yale)
EMBJ improvements
Active EMBJ, feedback;
Spontaneous self-break
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Single Molecule Junctions
 ODT (n=8), BDT
consistent single molecule G
10 nm
Au
 GBDT = 1.32 (±0.21) × 10-2 G0
Au
1 µm
Low bias (0-0.1V) conductance
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Single molecule junctions
G ∝ exp(-βd)
 Length dependence
 T independent tunneling
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
25
Single molecule junctions
 T independent tunneling
G (µS)
 Length dependence
I (nA)
1
0
-25
-0.1
0.1
BDT
DBDT
TBDT
0.0
0.1
V (V)
0.01
β = 1.54 per a phenyl ring (= 0.36 Å-1)
1
2
3
Number of Phenyls
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Transition Voltage Spectroscopy (TVS)
In high bias (FN tunneling),
 4d (2mΦ B 3 )1 / 2 
I ∝ V exp −

3

eV


2
rewriting,
4d (2mΦ B )1 / 2  1 
 I 
ln 2  ∝ −
 
3e
V 
V 
3
In low bias (direct tunneling),
1/ 2
 I 
 1  2 d ( 2 mΦ B )
ln 2  ∝ ln  −

V 
V 
J.M. Beebe et al, Phys. Rev. Lett. 97, 026801 (2006)
also Beebe, ACS Nano 2, 827 (2008); Roth, Appl. Phys. Lett. 92, 042107 (2008); Wang, JACS 131,
5980 (2009); Frisbie, Science 320, 1482 (2008); Yu, J. Phys.: Condens. Matter 20, 374114 (2008);
Liu, ACS Nano 2, 2315 (2008); ......
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
TVS: Barrier (FN) Tunneling versus Coherent Transport
ΦB
for HOMO transport

FN picture is physically incorrect

The coherent “resonant tail” picture surprisingly gives very similar “FN-type”
behavior (M. Araidai and M. Tsukada, Phys Rev. B 81, 235114 (2010); J. Chen
et al, Phys. Rev. B 82, 121412 (2010))
Orbital energies may be different by ~13% (I. Baldea, Chem Phys. 377, 15
(2010))

Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
TVS: Barrier Tunneling
versus Coherent Transport
Coherent model predicts length independent TVS Vtrans , contradicts FN model
(Huisman et al, Nano Lett. 9, 3909 (2009))
H. Song et al. J. Phys. Chem. C 114, 20431 (2010)
Vtrans = 1.86 V
2.4
-16
C8
C9
-18
C12
5
-22
-24
0
-5
0
10
-1
2.0
DC8
DC9
DC11
DC12
11
12
DC10
Vtrans (V)
C11
-20
I (nA)
ln(I/V2)
C10
1.6
C8
-2
20
0
V (V)
1.2
2
30
8
9
10
Number of Carbon
1/V (V )
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
…. however, it should change with varying degree of
conjugation (vs saturated)
SH
BDT
1.2
-12
SH
BDT
Vtrans (V)
ln(I/V2)
DBDT
-15
TBDT
1
SH
SH
0.9
SH
SH
I (µA)
BDT
-18
DBDT
0
TBDT
0.6
-1
0

DBDT
5
10
1/V (V-1)
-1
0
V (V)
15
TBDT
1
1
20
2
3
Number of Phenyls
Vtrans decreases with extended conjugation length
(HOMO−LUMO gap of π-conjugated organic molecules decreases with
increase in conjugation length)
H. Song et al, J. Appl. Phys. 109, 102419 (2011).
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
I(V) fit F (offset, linewidth)
1.5
1.0
I (µA)
0.5
where,
E0 (= |Ef – Em|)
Γ (= ΓL + ΓR)
I (V) plot
Experiment
Fit
HS
SH
0.0
-0.5
E0 = 0.92 eV
Γ = 0.046 meV
-1.0
-1.5
-2
-1
0
1
2
V (V)
PRB 82, 121412 (2010)
[ |Ef – Em|/Vtrans ] expt = 0.87
Experiment
Fit
ln(I/V2)
-14.0
-14.5
-15.0
FN plot
Vtrans = 1.06 V
-15.5
For symmetric molecular junctions,
[ |Ef – Em|/Vtrans ] theory ~ 0.87
Purdue Physics seminar
West Lafayette, IN
-4
-2
0
2
-1
1/V (V )
September 18, 2015
M. Reed (Yale)
4
Transistor transfer characteristics, ODT
a 15
b
-8
Al2O3/Al
10
High V
Low V
Au
VG = -3.3 V
-10
Au
VG = -2.8 V
5
-12
D
ln(I/V2)
I (nA)
S
G
0
VG = -3.3 V
VG = -2.1 V
VG = -1.6 V
VG = -1.1 V
-18
VG = -2.1 V
VG = 0.0 V
VG = -1.6 V
-10
-15
-2
-14
-16
VG = -2.8 V
VG = -2.6 V
-5
VG = -2.6 V
VG = -1.1 V
VG = 0.0 V
-1
0
1
-20
-22
2
V (V)
0
10
20
-1
30
1/V (V )
d
H. Song et al, Nature 462, 1039 (2009)
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Gate dependence of Vtrans, ODT
( )
(
c
)
d
ΦB
1.6
eVtrans (eV)
1.6 FND
EF
eV
Drain
Source
1.4
∆eVtrans/∆VG
= +0.25 eV/V
1.3
B
D
B
1.5
eVG,eff
HOMO
1.5
eV (eV)
1.7
eV
D eV
S
S
A
C
1.4
eV
D eV
S
S
1.3
D
D
1.2
1.2
1.1
-3.2
-2.8
-2.4
-2.0
-1.6
-1.2
VG (V)



C
A
DT
-0.8 -0.6 -0.4 -0.2
dln(I/V2)/d(1/V)
0.25
-0.3
eVG,eff (eV)
Vtrans scales linearly and reversibly with VG
Positive α for p-type (HOMO); negative α for n-type (LUMO)
Vtrans,0 = 1.93 V for ODT, which approximates EF - EHOMO  at
zero gate bias
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Gate lever arm – screening is dominant
S.S. Datta et al, Phys Rev. B79, 205404 (2009)
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Transistor transfer characteristics, BDT
D
b
6
0
-2
-6
S
D
G
-1
0
1
V (V)
D
c
2.0
Low V
VG = -3 V
-12
-14
-16
-4
S
1.6
eVtrans (eV)
2
D
High V
-10
ln(I/V2)
4
I (µA)
-8
VG = -3 V
VG = -2 V
VG = -1V
VG = 0 V
VG = 1 V
VG = 2 V
VG = 3 V
S
S
∆eVtrans/∆VG
= +0.22 eV/V
0.23
1.2
1.4 FN
1.2
1.0
0.8
DT
-0.5 0.0 0.5
0.8
VG = 3 V
0.4
-18
0
5
10
15
-1
20
-0.31
eV (eV)
a
eVG,eff (eV)
-3
-2
-1
1/V (V )
0
1
2
3
VG (V)
H. Song et al, Nature 462, 1039 (2009)
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
“n-type” (e.g., LUMO)
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Complementary transistors
HS
Purdue Physics seminar
SH
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Single Molecule IETS
Au-ODT-Au
I-V
Au-BDT-Au
DC
dI/dV
d2I/dV2
H. Song et al, Appl. Phys. Lett. 94, 103110 (2009)
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
15
7.8 mV
7.2 mV
6.1 mV
4.9 mV
4.3 mV
3.8 mV
0.34
FWHM (mV)
20
0.36 0.38
V (V)
40
30
ν(C-H)
δ(CH2)
ν(C-H)
50 K
40 K
30 K
20 K
10 K
4.2 K
0.34
0.36 0.38
V (V)
20
10
5
3
50
ν(C-H)
(d2I/dV2)/(dI/dV)
d
25
(d2I/dV2)/(dI/dV)
FWHM (mV)
c
v(C-S)
δ(CH2)
v(C-C)
ν(Au-S)
ODT
γ(CH2)
ODT IETS
4.2 K
4
5
6
7
8
AC modulation (RMS value) (mV)
Purdue Physics seminar
West Lafayette, IN
10
0
7.8 mV
10
20
30
40
50
Temperature (K)
September 18, 2015
M. Reed (Yale)
IETS (VG), ODT
Wavenumbers (cm-1)
0.5
eVG,eff = -0.75 eV
eVG,eff = -0.5 eV
eVG,eff = -0.25 eV
eVG,eff = 0 eV
b
(d2I/dV2)/(dI/dV)
0.37
0.8
0.4
ν(C-H)
0.3
δs(CH2)
ν(C-S)
1.0
δr(CH2)
ν(C-C)
γw(CH2)
ν(Au-S)
(d2I/dV2)/(dI/dV) (V-1)
1.5
500 1000 1500 2000 2500 3000 3500
eV (eV)
0
ν(C-H)
a
0.2
δs(CH2)
ν(C-C)
0.1
D
S
0.0
0.1
δr(CH2)
ν(Au-S)
G
0.0
ν(C-S)
γw(CH2)
0.2
0.3
V (V)
0.4
0.0
0.00
-0.25
-0.50
eVG,eff (eV)
-0.75
ODT: no electrode-orbital coupling, far from resonant system
BDT?
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Near-resonant IETS
(Persson & Baratoff, PRL 59, 339 (1987), & others)
near eV = Ω for a molecular vibration, the change η in the total normalized
tunneling conductance is (orbital energy EM , width Γ, coupling δE );
 ( EM − EF − Ω) 2 − (Γ / 2) 2
η
θ (eV − Ω)

( EM − EF ) 2 + (Γ / 2)  ( EM − EF − Ω) 2 + (Γ / 2) 2
( EM − EF − Ω)Γ
eV − Ω 
1
−
ln

∆ 
π ( EM − EF − Ω) 2 + (Γ / 2) 2
δ E2
Implications:
Far from resonant – no change in
intensity, for either small
linewidth or large spacing
Near resonant – enhancement in
intensity, increasingly “Fanotype” lineshapes
Mii et al, Phys Rev B 68, 205406 (2003)
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
BDT: resonantly enhanced IETS
Wavenumbers (cm-1)
2000
2500
dip
0.2
S
0
6
S
HOMO
VG,eff
D
3
0
eVG,eff = -0.22 eV
40
3
2
1
0
S
HOMO D
VG,eff
20
0
dip
dip
0.1
0.0
Purdue Physics seminar
0.1
V (V)
0.2
-0.35 -0.40 -0.45
eVG,eff (eV)
c
5
ν(18a)
Persson & Baratoff
model
Experiment
Fit
4
3
0.3
West Lafayette, IN
γ(C-H)
peak
D
G
ν(18a)
peak
eVG,eff = -0.66 eV
S
ν(8a)
peak
eVG,eff =
0 eV
-0.22 eV
-0.66 eV
d2I/dV2 (a.u.)
1
eV (eV)
D
HOMO
VG,eff
eVG,eff = 0 eV
3
2
1
0
16.5
2
Ω
0
(d2I/dV2)/(dI/dV)
-5.1
(d2I/dV2)/(dI/dV) (V-1)
(d2I/dV2)/(dI/dV) (V-1)
1
1500
b
η (%)
2
1000
ν(18a)
ν(Au-S)
3
500
γ(C-H)
0
ν(8a)
a
0.12
-0.3
-0.4
V (V)
-0.5
eVG,eff (eV)
September 18, 2015
0.16
-0.6
M. Reed (Yale)
Molecular engineering: p-type transport (thiol endgroup)
Source
S

LUMO
X

S Drain

EF
I
V
Gate
Source HOMO Drain
4
0
-2
+0
.
1.1
Vtrans
I (µA)
08
1.2
2
-8
VG =
-2.4 V
-2.0 V
-1.6 V
-1.2 V
-0.8 V
-0.4 V
0V
0.4 V
0.8 V
1.2 V
1.6 V
2.0 V
2.4 V
2.8 V
=
ln(I/V2) (a.u.)
VG
-4
SH: e-donating character
shifts frontier MOs upwards
HOMO closest to EF
α
1.0
0.9
-1
-6
0
V (V)
-4
0.8
-3 -2 -1 0 1 2 3
VG (V)
1
-2
0
-1
2
4
6
8
1/V (V )
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Substituent p-type molecules
BDT2Me
SH
2
+0
.1
3
0.9
=
HS
1.0
Vtrans (V)
CH3
ln(I/V2) (a.u.)
H3C
α
0.8
F
0
1.4
4
2
b
5
HS
SH
0.9
Cl
0.7
α
-3 -2 -1 0
VG (V)
5
Cl
Purdue Physics seminar
0
2
4
1/V (V-1)
West Lafayette, IN
8
Cl
HS
1.0
0.8
6
Cl
6
1
8
VG =
-2.4 V
-2.2 V
-2.0 V
-1.8 V
-1.6 V
-1.4 V
-1.2 V
-1.0 V
-0.8 V
-0.6 V
-0.4 V
-0.2 V
0V
0.2 V
0.4 V
0.6 V
SH
Cl
Cl
VG =
-2.0 V
-1.5 V
-1.0 V
-0.5 V
0V
0.5 V
1.0 V
BDT4Cl
1.6
Vtrans (V)
Cl
d
=
Cl
F
Vtrans (V)
F
4
1/V (V-1)
BDT1Me
4
ln(I/V2) (a.u.)
SH
α
1.1
2
SH
F
HS
0
8
CH3
HS
F
6
1/V (V-1)
3
1.2
-2 -1 0 1 2
VG (V)
ln(I/V2) (a.u.)
SH
1.3
0
1
VG (V)
+0
.0
9
HS
2
VG =
-2.0 V
-1.5 V
-1.0 V
-0.5 V
0V
0.5 V
1.0 V
1.5 V
2.0 V
2.5 V
BDT4F
0.7
-1
F
+0
.0
7
VG =
-0.6 V
-0.4 V
-0.2 V
0V
0.2 V
0.4 V
0.6 V
0.8 V
1.0 V
1.2 V
SH
=
H3C
HS
+0
.1
6
1
SH
1.4
=
SH
HS
F
F
4
Vtrans (V)
HS
c
CH3
1
ln(I/V2) (a.u.)
a
CH3
α
1.2
1.0
-2 -1 0 1 2
VG (V)
0
September 18, 2015
2
4
6
8
1/V (V-1)
M. Reed (Yale)
α
0.9
0
1/V (V-1)
2
-1
0
1
VG (V)
4
6
-6
VG =
-0.6 V
-0.4 V
-0.2 V
0V
0.2 V
0.4 V
0.6 V
0.8 V
1.0 V
1.2 V
-2
0
1/V (V-1)
+0
.1
3
0
VG (V)
4
6
8
+0
.0
9
1.1
α
1.0
0.9
-4
1
-2 -1 0 1 2 3
VG (V)
-2
0
1/V (V-1)
2
2
4
West Lafayette, IN
+0
.1
4
=
-1
4
0
VG (V)
1
6
8
-8
-1
-6
0
V (V)
-4
1.2
1.1
1.0
0.9
0.8
0.7
α
-1
1
-2
0
1/V (V-1)
2
4
0
VG (V)
6
1
8
VG =
-2.1 V
-1.8 V
-1.5 V
-1.2 V
-0.9 V
-0.6 V
-0.3 V
0V
0.3 V
0.6 V
0.9 V
1.2 V
1.5 V
1.8 V
2.1 V
2.4 V
1.2
0
V (V)
0
1/V (V-1)
0
-6
1
1.3
-1
-2
3
=
2
Vtrans
I (µA)
-1
1
-4
-4
-3
=
I (µA)
Vtrans
0
V (V)
0.7
1
6
α
0.8
-6
0
V (V)
VG =
-0.4 V
-0.2 V
0V
0.2 V
0.4 V
0.6 V
0.8 V
0.7
-1
-6
ln(I/V2) (a.u.)
0.9
-8
8
-1
+0
.2
1
-2
-2
Purdue Physics seminar
α
=
-4
0
-6
0.9
0.8
Vtrans
1
I (µA)
0
V (V)
ln(I/V2) (a.u.)
-1
1.0
3
2
1
0
-1
-2
-3
1.0
0
VG =
-0.9 V
-0.6 V
-0.3 V
0V
0.3 V
0.6 V
0.9 V
1.2 V
1.5 V
1.8 V
0.8
2
-8
1.1
3
-3
4
-4
6
Vtrans
1.0
I (µA)
+0
.1
4
1.1
-6
ln(I/V2) (a.u.)
-8
1.2
=
3
2
1
0
-1
-2
-3
Vtrans
I (µA)
ln(I/V2) (a.u.)
BDT,2Me
ln(I/V2) (a.u.)
VG =
-1 V
-0.5 V
0V
0.5 V
1V
1.5 V
6
September 18, 2015
M. Reed (Yale)
Substituent p-type molecules
e-donating groups
CH3
HS
SH
e-withdrawing groups
1.4
1
LUMO
1.3
H3C
EF
CH3
SH
2
Vtrans,0 (V)
HS
1.2
Source HOMO Drain
1.1
X = 4Cl
X = 4F
1.0
HS
SH
3
0.9
X = CH3
α = +0.06 to +0.23
X = 2CH3
F
F
0.8
1
HS
F
F
Cl
Cl
HS
Cl
SH
4
SH
5
2
3
4
5
Molecules
Cl
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Molecular engineering: n-type transport (cyanide endgroup)
X
Source
NC
LUMO

EF

CN Drain

I
V
Source
Gate
HOMO
VG
ln(I/V2) (a.u.)
Drain
CN: e-withdrawing character
shifts frontier MOs downwards
LUMO closest to EF
0.1
1.2
1.0
.
-0
14
Vtrans
=
I (µA)
α
0.0
0.8
0.6
-0.1
-8
-1
-6
0
V (V)
-4
1
-3 -2 -1 0 1 2 3
VG (V)
-2
0
-1
2
4
6
8
VG =
2.7 V
2.4 V
2.1 V
1.8 V
1.5 V
1.2 V
0.9 V
0.6 V
0.3 V
0V
-0.3 V
-0.6 V
-0.9 V
-1.2 V
-1.5 V
-1.8 V
-2.1 V
1/V (V )
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Substituent n-type molecules
6
H3C
CH3
CN
F
F
BDCN4F
1.2
=
2
4
6
0.8
-2 -1 0 1 2
VG (V)
8
0
2
4
1/V (V-1)
7
b
NC
F
NC
F
F
Purdue Physics seminar
0.8
0
2
1.2
4
6
8
1.0
0.8
0.6
-3 -2 -1 0 1 2 3
VG (V)
-1 0 1 2 3
VG (V)
1/V (V-1)
West Lafayette, IN
BDCN4Cl
4
.1
-0
Cl
1.0
Cl
Cl
=
Cl
10
1.2
CN
α
CN
1.4
5
.1
-0
NC
VG =
2.4 V
2.1 V
1.8 V
1.5 V
1.2 V
0.9 V
0.6 V
0.3 V
0V
-0.3 V
-0.6 V
=
Cl
NC
α
Cl
9
Cl
Cl
CN
BDCN1Me
ln(I/V2) (a.u.)
CN
10
d
CH3
Vtrans (V)
F
8
VG =
2.1 V
1.8 V
1.5 V
1.2 V
0.9 V
0.6 V
0.3 V
0V
-0.3 V
-0.6 V
-0.9 V
-1.2 V
-1.5 V
-1.8 V
-2.1 V
-2.4 V
8
Vtrans (V)
CN
6
1/V (V-1)
ln(I/V2) (a.u.)
NC
3
.1
-0
1.0
-3 -2 -1 0 1 2 3
VG (V)
0
α
9
.0
-0
7
1.6
1.5
1.4
1.3
1.2
1.1
=
CN
BDCN2Me
α
NC
VG =
3.0 V
2.4 V
1.8 V
1.2 V
0.6 V
0V
-0.6 V
-1.2 V
-1.8 V
-2.4 V
NC
Vtrans (V)
H3C
F
F
9
CN
Vtrans (V)
CN
NC
ln(I/V2) (a.u.)
NC
c
CH3
6
ln(I/V2) (a.u.)
a
CH3
0
2
4
1/V (V-1)
September 18, 2015
6
8
VG =
2.7 V
2.4 V
2.1 V
1.8 V
1.5 V
1.2 V
0.9 V
0.6 V
0.3 V
0V
-0.3 V
-0.6 V
-0.9 V
-1.2 V
-1.5 V
-1.8 V
-2.1 V
M. Reed (Yale)
Substituent n-type molecules
e-donating groups
CH3
e-withdrawing groups
1.5
NC
CN
LUMO
6
1.4
H3C
EF
CH3
NC
CN
7
Vtrans,0 (V)
1.3
1.2
Source
Drain
HOMO
X = 2CH3
1.1
X = CH3
1.0
NC
CN
8
0.9
X = 4F
α = -0.05 to -0.21
F
F
6
NC
F
F
Cl
Cl
NC
Cl
X = 4Cl
0.8
CN
9
CN
10
7
8
9
10
Molecules
Cl
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Decoupled contact-molecule system
Native conductance is set by endgroup
Molecular conductance set by orbital position (T~1/(E-EF)2)
LUMO
CN- contact
HOMO
S- contact
s=9.5x10-3/V2
s=7.5x10-4/V2
GS/GCN = slopeS/slopeCN = 13
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)
Summary

Molecular transistor
with orbital gating

Coherent transport,
resonant coupling

“n” & “p” type

Molecular engineering

The future: “active” functional molecular systems
Purdue Physics seminar
West Lafayette, IN
September 18, 2015
M. Reed (Yale)