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Untitled


Workshop facilitation, logistics,
&
report
editing

and

publishing

provided

by

the
World

Technology

Evaluation

Center
,
Inc.
B
UILDING
E
LECTRONIC
F
UNCTION INTO
N
ANOSCALE
M
OLECULAR
A
RCHITECTURES


Report of a National Science Foundation Workshop
Ballston, Virginia, 78 June 2007

Workshop Co-Chairs
Héctor D. Abruña
Cornell University
Mark A. Ratner
Northwestern University
Roger D. van Zee
National Institute of Standards and Technology

Steering Committee
Carlos A. González
National Institute of Standards and Technology
Cherie R. Kagan
University of Pennsylvania
Duncan R. Stewart
Hewlett Packard Laboratories
Amy V. Walker
Washington University

Writing Group
James D. Batteas
Texas A&M University
Christopher E. D. Chidsey
Stanford University
Cherie R. Kagan
University of Pennsylvania
Tamar Seideman
Northwestern University
Building Electronic Function into Nanoscale Molecular Architectures

A
CKNOWLEDGEMENTS

This workshop was organized on a tight time schedule. It could not have been a success had not so
many people worked so hard.
The workshop Steering Committee suggested and selected the participants and speakers. The
Writing Group drafted the chapters of this report. Specifically, Cherie Kagan drafted Chapter 2,
Molecules and Electronic Applications; Chris Chidsey drafted Chapter 3, Making Molecular
Architectures: Molecules & Assembly; Jim Batteas drafted Chapter 4, Molecular Measurements:
Tools & New Technologies; and Tamar Seideman drafted Chapter 5, Understanding
Fundamentals & Modeling Behaviors. Nancy Forbes integrated their inputs, creating a cohesive
document. Nicolle Rager Fuller created and improved many of the figures in this report. Because
this group worked with incredible speed, this report was completed in less than two months.
Many WTEC staff members contributed to the workshops success. Duane Shelton directed the
overall project, with Hassan Ali serving as the WTEC project manager. Mike DeHaemer kept the
program and report production on schedule. Pat Johnson edited this report. Roan Horning handled
all matters related to computers and video displays. Halyna Paikoush attended to many
administrative details. Thanks go to them all.
Thanks go also to the Marymount University Conference Center and Liz Onesty for providing an
excellent venue for the workshop.
Finally, thanks go to Luis Echegoyen, Director of the Division of Chemistry at the National
Science Foundation, for his enthusiasm; to Jeff Krause, Program Officer for Theoretical and
Computational Chemistry, for shepherding the workshop proposal through review; and to the NSF
Division of Chemistry, Division of Materials Research, and Engineering Directorate for funding
the workshop.







The

National

Science

Foundation

sponsored

this

workshop

through

grant

CHE-0733717

to

WTEC.



Any opinions, findings, conclusions, or recommendations contained in this material are those of the workshop
participants and do not necessarily reflect the views of the United States Government, its agencies, or the authors' parent
institutions.
Copyright 2007 by WTEC, Inc., except as elsewhere noted. The U.S. Government retains a nonexclusive and
nontransferable license to exercise all exclusive rights provided by copyright. Copyrights to graphics or other individual
contributions included in this report are retained by the original copyright holders and are used here under the
Government's license and by permission. Requests to use any images must be made to the provider identified in the
image credits.
First Printing: August 2007.
Building Electronic Function into Nanoscale Molecular Architectures
i
P
REFACE

Molecule-based electronics holds substantial promise for application in fields from information
technology to environmental management, from medicine to energy transduction. The idea of using
molecules in electronic systems has been around for some time. But it was not until the tools of
nanotechnology became widely available that serious work began toward implementing that idea.
During the past decade, remarkable progress has been made. Two-terminal molecular rectifiers
have been constructed, three-terminal single-molecule transistors demonstrated, and molecular
recognition transducers developed. Complex theoretical formalisms have been reduced to
algorithms. New sensing and switching paradigms have been proposed. In short, the progress has
been substantial. The promise of using molecules in electronic systems remains strong.
After more than ten years of solid progress in molecular electronics research, many of us working
in the field concluded that the time had come to assess where things stood and where things should
go. Some of the early findings and claims no longer seemed to represent general phenomena. Some
of the most interesting characteristics of nanoscale molecular junctions, at first assumed to be
molecular in origin, had been linked to interface effects. The metal-thiol attachment chemistry,
almost ubiquitous in device prototypes, had long been known to be labile, prone to oxidation, and
to result in a large mismatch between the metallic and molecular energy levels. In addition, sharp-
penciled engineers had raised issues of integration, heat management, and reliability. But the need
for inexpensive, ubiquitous sensors, information systems, adaptable neural networks, and
electronics components is large and growing. The progress of the past decade has only made
molecular electronics more interesting as a potential solution to those challenges.
For the science of molecular electronics to be transformed into a technology, a strong scientific and
engineering understanding must underpin the observed behavior of molecule-containing junctions.
Together with the World Technology Evaluation Center and the National Science Foundation, we
put together this workshop to address just that topic. The objectives were to evaluate the state of
the art, identify challenges and opportunities, and propose research directions and targets. The
horizon we proposed was long-term, ten or more years out. The scope was to be broad. We
considered a wide range of scientific approaches and engineering solutions, though the workshop
was organized around just three themes: (1) molecules and self-assembly, (2) measurements of
electronic function in molecular systems, and (3) theory. Or more simply put, the themes were the
making, measuring, and modeling of molecular electronic functionality. The workshop
spanned two days, encompassing a mixture of presentations and breakout sessions.
By our reckoning, the workshop was a success. The discussions were extensive and intense.
Workshop participants were diverse in every possible way. The themes that emerged are outlined
in this report, which provides a map to expanding the understanding and application of the
electronic function of molecules and molecular architectures.

Héctor D. Abruña
Mark A. Ratner
Roger D. van Zee
Cornell University
Northwestern University
National Institute of
Ithaca, New York
Evanston, Illinois
Standards and Technology
Gaithersburg,
Maryland

ii

Building Electronic Function into Nanoscale Molecular Architectures

Building Electronic Function into Nanoscale Molecular Architectures
iii

T
ABLE OF
C
ONTENTS

Preface................................................................................................................................................................i

Executive Summary .........................................................................................................................................v

1. From Molecules to Competitiveness

Building Electronic Function into Molecular Architectures..........................................................................1

The Workshop ...............................................................................................................................................2

The Report .....................................................................................................................................................3

2. Molecules & Electronic Applications

Molecules & Moores Law............................................................................................................................5

Electronic Applications of Molecules............................................................................................................6

The Science and Engineering of Molecular Electronics................................................................................9

3. Making Molecula