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MOLECULAR ELECTRONICSMOLECULAR ELECTRONICS
A Presentation to the Visiting Committee on Advanced Technology
On a New Competence-Building Project in
1970 1980 1990 2000 2010 2020103
104
105
106
107
108
Year
0.01
0.1
1
10Pentium 4
80486
80286
4004
Num
ber o
f Tra
nsis
tors
Per
Chi
p
Feature Size (µm)
“Moore’s Law”
11 December 2001
Molecular Electronics?Molecular Electronics?
•What is “Molecular Electronics?”•Why now?
•Who are the players?•How can NIST help?
•Our team approach.•The first year’s progress.
•The road ahead.
Molecular ElectronicsMolecular Electronics—— moletronicsmoletronics ——
A new technology that uses molecules to perform the function of electronic components.
amplifier
wire
D
A
diod
esw
itchH2N
NO2
SH
Moletronics in the NewsMoletronics in the News
C&E News
Washington Post
Nature
Physics Today
Moletronic Moletronic ComponentsComponentsTransistors
Lucent Electrically-ActiveMolecules
Rice, Univ. of Alabama, UCLA
“I was one of the biggest skeptics. Now I believe that this is the inevitable wave of the future.” —R. S. Williams, Hewlett-Packard
NC
N
C
N
C16H33
C
N
junction diode
MemoryMEC, Harvard
RTD
S
S
OO
S SS S
O
OO O O O
O O
N
N
N
N
+
+
+
+
Vc
V1
V2Vout
Logic FunctionHewlett-Packard, UCLA, Mitre Corp. Nanotube FET
IBMswitch
0.013 µm
16441945
1948
1959
2016
1970 1980 1990 2000 2010 2020103
104
105
106
107
108
Year
0.01
0.1
1
10Pentium 4
80486
80286
4004
Feature Size (µm)Tr
ansi
stor
s pe
r Chi
p
Device Physics Changes
Approaching Fundamental LimitsApproaching Fundamental Limits
ENIAC
Transistor
IC
Moore’s LawComputational Paradigm Shifts
A new components technology is required to maintain the uninterrupted succession of smaller and faster electronic devices.
• Even big molecules are small.• Functional control through synthesis.• Self-assembling devices.
Why Use Molecules?Why Use Molecules?
metal
HS - R - X
MolecularLengths
1n
10n
100n
1µ
10µ
1970 1980 1990 2000 2010 2020
Year
Line
wid
th (m
)
Classical
Quantum
NDR RS
NO2
NH2
H2N
NO2
S
NDR – Negative Differential ResistanceR – Resistor
10 nm
How Molecules ConductHow Molecules ConductConventional Electronics
insulator
conductor
doped semiconductors
Molecular Electronics
insulator–S—CH2—CH2—CH2 — S –
conductor
–S—CH —C —CH — S –
–S—CAc —C —CDn — S –
substituted molecules
Moletronic Moletronic ComponentsComponents
NC
N
C
N
C16H33
C
N
Vc
V1
V2Vout
Logic FunctionHewlett-Packard, UCLA, Mitre Corp.
TransistorsLucent
junction diode
OO
S SS S
O
OO O O O
O O
N
N
N
N
+
+
+
+
switch
MemoryMEC, Harvard
Nanotube FETIBM
RTD
S
SElectrically-ActiveMolecules
Rice, Univ. of Alabama, UCLA
“I was one of the biggest skeptics. Now I believe that this is the inevitable wave of the future.” — R. S. Williams, Hewlett-Packard
A Role for NISTA Role for NIST
To develop the measurement tools and data necessary to measure, model, and control the flow of charge through molecules and ensembles of molecules.
“To knowledge by measurement.” — Kammerlingh Onnes, Leiden Univ.
Grand ChallengesGrand Challenges
•Develop Moletronics Metrology
• Correlate Structure and Function
Science, vol. 286, p. 1551Sci. Am. June 2000
“The field suffers from an excess of imagination and a deficiency of accomplishment.” —J. Hopfield, Princeton University
Our Role/The ChallengeOur Role/The Challenge—— What does it mean? How do to make it useful? ——
•What is the physical basis for electrical activity in moletronic systems?
•How are electrical quantities reliably measured at molecular dimensions?
•What measurements and data are needed to speed this technology to market?
Our GoalsOur Goals• To advance the measurement sciences and
standards as applied to moletronics.– Quantitative measurement and understanding
of molecular conductance– Validated models– Characterized prototype– Test vehicle for molecular components
• To create a nucleation center for speeding the development of moletronics technology.
“New directions in science are launched by new tools much more often than by new concepts.” — Dudley Herschbach, Harvard Univ.
A Multidisciplinary EffortA Multidisciplinary EffortChemistryChemistry
••SelfSelf--AssemblyAssembly••StructureStructure••MechanismsMechanisms••ModelingModeling
Electrical EngineeringElectrical Engineering••ContactsContacts••IntegrationIntegration••PerformancePerformance••ReliabilityReliability
M. TarlovR. van ZeeM. Tarlov
R. van ZeeJ. SuehleC. RichterJ. SuehleC. Richter
S. RobeyR. van ZeeS. Robey
R. van Zee
C. RichterC. RichterC. GonzalezC. Gonzalez
Research EmphasesResearch EmphasesElectrical Properties of
Small Ensembles
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
Structure of Electrically-Active, Molecular Films
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
Theory
g(E) = ∆D ∆ Aπhγ2
2e2T2
NH2
NO2
S
Electrical Properties ofLarge Ensembles
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
1000 1500 2000
In KBr Pellet
Grown from Vapor
Grown in Solution
wavenumber (cm-1)
CH2
CH2
SH
Sangle
- Studying Film Structure --
0 30 60 90
A.M. Bratkovsky, HPRLPhys. Rev. B, 64, 195413
AngleC
ondu
ctio
n
Resistance of Small EnsemblesResistance of Small Ensembles
18 MΩ±12 MΩ
CH2
CH2
SH
SHR.P. Andres et al., Purdue
Science, 272, p.1323
Resistance
p-benzenedimethanethiol
CH2
CH2
SH
S
CH2
CH2
SH
S
CH2
CH2
SH
S
CH2
CH2
SH
S
CH2
CH2
SH
S
CH2
CH2
SH
S
From Molecules to DevicesFrom Molecules to Devices
Ultra-thin SiO22 nm - 10 nm
No. of Molecules(10 nm - 100 nm)
Molecular Length(2 nm – 10 nm)
Field SiO2
Bottom Electrode
Top Electrode
Low Temp. Au
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
NH2
NO2
S
Top Electrode
Bottom Electrode
- Building Test Structures --
~20 µm
SiO2/Si3N4
~40 nm
-2 -1 0 1 2 3 40
10
20
30
40
Curr
ent (
pA)
Applied Voltage (V)
Testing Device PerformanceTesting Device Performance
D.R. Stewart et al., HPRLBull. Am. Phys. Soc., 46, p.1
CH3(CH2)18CO2H
Al
Al
Ti
Al2O3
OHO
OHO
OHO
OHO
OHO
OHO
OHO
OHO
OHO
OHO
OHO
OHO
OHO
OHO
OHO
OHO
0.72
0.73
0.74
0.75
Capa
cita
nce
(pF)
“1”High
current“0”
Low current
CrossBars
Probe Station
- Reliable Electrical Measurements --Device OperatingCharacteristics
Kohn-Sham Equations
F[p(r)] = Ehf [p(r)] + Ex [p(r)]
T+Vhf(r)+Vn(r) + Vx(r) ϕi = ε ϕ i
0.0 0.5 1.0 1.5 2.0 2.5-0.1
0.0
0.1
0.2
Curr
ent
Charge on Rings (AU)
Applied Voltage (V)
Upper Ring - RU Middle Ring - RM Lower Ring - RL
Charge on Rings
Modeling Molecular SwitchesModeling Molecular Switches
• Significant charge density localization at voltages below 2.1 V (no current).
• Near 2.1 V maximum de-localization of charge density (maximum current).
• Above 2.1 V charge density localization occurs again (no current).
–S—RL—RM—RU <2.1 V
–S—RL —RM —RU ~2.1 V
NH2
S
NO2
RU
RM
RL
- Understanding Electrical Function and Molecular Structure --
–S—RL—RM—RU >2.1 V
The Road AheadThe Road Ahead
•Small Ensemble Conduction Experiments
•Test Structure Assessment
•Electronic Structure Characterization
•Conduction Modeling
Leveraging our ResourcesLeveraging our Resources•Nanocell Molecular Computer Collaboratory(Molecules, Electrical Characterization)
–J. M. Tour, Rice University–M.A. Reed, Yale University–P.S. Weiss, Penn State University
•Hewlett-Packard Research Labs(Devices, Electronic Structure)
–R.S. Williams–P.J. Kuekes
•Naval Research Laboratory(Molecules)
–R. Shashidhar
Molecular Electronics!Molecular Electronics!•Important Technology
•Revolutionary•Timely
•Critical Role for NIST
• Interdisciplinary Team•Strong Partnerships with Industry & Universities
Strategies for Success