|Small focus brings big rewards
|by Patrick Young
Focusing on small things in innovative ways figured prominently
in earning high honors for 10 researchers, the winners of six prized
awards in physics.
The American Physical Society (APS) awarded the Irving Langmuir
Prize, which honors interdisciplinary research in chemistry and
physics, to Phaedon Avouris of the IBM Thomas. J. Watson
Research Center. He was recognized for his pioneering studies of
nanostructures and atomic-scale phenomena at surfaceswork
that has involved chemical physics, surface chemistry and physics,
molecular electronics, and nanoscience. Phaedon Avouriss
career has, in many ways, defined the progress in atomic- scale
manipulation and nanotechnology, and the science behind it,
says Tony F. Heinz, professor of electrical engineering and physics
at Columbia University.
Avouriss accomplishments include the first demonstration
of resonant electron scattering of molecules in the absorbed state.
His explorations of semiconductor surface chemistry led to many
important findings, including the correlation of surface reactivity
with the presence of dangling bonds, and the discovery that, contrary
to prevailing opinion, clean silicon surfaces are very reactive
at cryogenic temperatures.
|Figure 1. Atomic-force-microscope
cross-sectional image of a carbon nanotube ring that is
bridging two gold electrodes.
( Phaedon Avouris, IBM)
|In the 1980s, Avouris introduced scanning tunneling
microscopy (STM) to study surface chemistry atom-by-atom, and
he developed chemically assisted field desorption, which allows
the selective breaking of individual covalent bonds and the
use of an STM tip to move individual strongly bonded atoms.
Since the discovery of carbon nanotubes (CNTs), Avouris has
focused largely on their electronic properties. His group fabricated
the first field-effect transistor using a single CNT as the
transistors channel and went on to make significant improvements
in these transistors. A great deal of fascinating science
lies behind these accomplishments, from learning how to manipulate
and contact nanotubes to in situ nanotube modification and doping,
Arthur Ashkin received the 2003 Joseph F. Keithley
Award for Advances in Measurement Science. APS honored him for his
pioneering work in laser cooling and the trapping of atoms and particles,
as well as his invention of optical tweezers and their use to measure
the physical forces generated by biological molecular motors. Ashkins
theoretical and experimental contributions, made over more than
three decades at Bell Laboratories, have had a profound impact on
atomic, soft condensed- matter, and biological physics.
Art was the first to demonstrate and understand how microscopic
particles can be trapped, accelerated, and levitated with laser
light, says Steven Chu, professor of physics and applied physics
at Stanford University. He and his collaborators demonstrated
that optical trapping could be done with a single focused laser
beam, a technique now known as optical tweezers. He then went on
to show how individual live cells, and even organelles within cells,
can be moved and held in the optical trap without damage. In short,
the introduction of force as another experimental measurable parameter
in the study of microscopic and molecular systems was due to Art.
Ashkins invention of the optical tweezers led to important
experiments. These include studies of the rotary motor that propels
the flagella of E. coli bacteria, the interaction of the muscle
proteins actin and myosin, the enzymes that cleave the genetic molecules
DNA and RNA, and the packing of DNA into the outer coatings of viruses.
His early work also included studies of sharp Mie resonances in
glass microsphereswork revived by other researchers 20 years
later to study microlasers and cavity quantum electrodynamics.
Figure 2. Representation (upper
image) of light emitted from a diode formed by crossing
p-doped and n-doped nanowires, shown with their electrodes
in the lower atomic-forcemicroscope image.
(X. Duan and Y. Huang Lieber Group, Harvard University)
APSs Polymer Physics Prize went to Andrew J.
Lovinger for his contributions to fundamental understanding
of structure, morphology, and properties in technologically
important polymerswork he started at Lucent Technologies
Bell Laboratories and has continued on his own time since joining
the National Science Foundation (NSF) in 1995. His quarter-century
of contributions stems from five research areas: ferroelectric
polymers, silicon-based polymers, high-temperature and high-strength
engineering polymers, syndiotactic polypropylene, and organic-
and polymerbased transistors. Andy had been at the center
of microstructural advances in a host of technologically significant
semicrystalline polymers, says Edwin L. Thomas of the
Massachusetts Institute of Technology. Even though now
full-time at NSF, he continues his research with unabated dedication,
and he has published 44 papers during this time.
Since the early 1990s, Lovinger has focused on developing organic-
and polymer- based transistors. During this time, he and his co-workers
have carried out key structural and morphological studies that have
provided a deeper understanding of these novel materials. They have
shown that the critical issue for optimizing semiconducting properties
is to orient the molecules so that their pp orbital overlaps
lie along the source-to-drain direction of the transistor. Lovinger
has also demonstrated the crucial role of crystal morphology, order,
and defects on the devices semiconducting properties, and
has shown that soluble regioregular polythiophene derivatives yield
printable semiconducting polymeric field-effect transistors that
have good flexibility and processing characteristics.
His work combines deep insight into the fundamental factors
for chain packing, with world-class experimental skills in transmission
electron microscopy, electron and X-ray diffraction, and atomic
force microscopy, says Stephen Z. D. Cheng of the University
of Akron. He is a great experimentalist, clever and novel,
and a great leader.
Charles Lieber of Harvard University earned the APS
James C. McGroddy Prize for his outstanding contributions in nanostructured
and functional nanostructured materials. He has been spectacularly
successful in developing methods of incorporating his materials
into prototype devices that yield solid, physics-based measurements,
and in taking the first steps toward building prototype integrated
circuits using self-assembly, says Harvard colleague George
Lieber began in the mid-1980s with the study of carbon nanotubes,
and over the years he systematically examined their electronic properties
and how small differences in their molecular structure affect these
properties, including whether they are insulators or semiconductors.
He also addressed the difficulty of growing nanotubes and assembling
them into primitive devices. Lieber developed a way to reproducibly
grow nanorods of single crystalline silicon and compound semiconductors
using liquidvaporcatalytic growth, and to demonstrate
an impressive range of new devices and phenomena. Last year, for
example, he and his team laid down a simple crossbar arrangement
of silicon and gallium nitride nanowires that allowed communication
among the wires and demonstrated that logic functions for complex
circuits can be constructed using this bottom-up assembly method.
Both the materials that he is synthesizing and the strategies
that he is demonstrating will have enormous impact on the future
of materials science, predicts Whitesides. His work
may change device physics and perhaps, ultimately, electronics in
a most profound way.
Physicist C. Paul Robinson received the APSs
2003 George E. Pake Prize in recognition of his leadership as director
of Sandia National Laboratories, his arms-control negotiating skills,
and his pioneering contributions to the development of highexplosives
lasers, e-beam-initiated chemical lasers, and molecular laser-isotope
|Figure 3. C. Paul
Robinson, director of Sandia National Laboratories, was
awarded the George E. Pake Prize for his international
leadership roles and laser research.
(Randy Montoya, Sandia National Laboratories)
|Robinson spent much of his early career at Los
Alamos National Laboratory, where his research included nuclear
weapons, fusion, nuclear-materials safeguards, and arms-control
verification. From 1988 through most of 1990, he held the rank
of ambassador and led the U.S. delegation to the Nuclear Testing
Talks with the Soviet Union in Geneva, Switzerland. The negotiations
produced two major agreements, the protocols to the Threshold
Test Ban Treaty and the Peaceful Nuclear Explosions Treaty.
Both were ratified unanimously by the U.S. Senate and
remain in force today, testifying to his exceptional ability
to achieve broad acceptance of government operations and policies
both nationally and internationally, says Alton D. Romig,
Sandias chief technology officer and vice president for
science and technology and partnerships.
In 1995, Robinson became Sandias director and has led efforts
to increase its ties to industry and its transfer of technology
to small businesses. Sandia has created more than 350 advanced
research projects and 1,200 partnerships with small business, as
well as providing short-term technical assistance to many companies,
Romig said. Dr. Robinsons leadership has greatly advanced
The 2002 Agilent Europhysics Prize went to Dante Gatteschi
and Roberta Sessoli of the University of Florence in Italy,
Bernard Barbara and Wolfgang Wernsdorfer of the Louis
Néel Laboratory in Grenoble, France, and Jonathan Friedman
of Amherst College. The European Physics Society (EPS) cited the
five for their exploration of the quantum effects in the mag netic
dynamics of molecular nanomagnets. This observation of quantum
behavior at an intermediate scale between microscopic and macroscopic
is an important breakthrough that has revived the field of mesoscopic
magnetism, the EPS said.
Molecular nanomagnets contain a small number of magnetic atoms
and carry a global collective magnetic moment. They have been studied
since the early 1980s, and Gatteschi and Sessoli have played a key
role in the precise characterization of their magnetic structures.
One example is their work with the spin-cluster molecule [Mn12O12(CH3COO)16(H2O)],
informally called Mn12. Below 3 K, the molecules mesoscopic
magnetic moment is blocked along one of the directions of its anisotropy
axis; applying a magnetic field reverses the moment at about 9.6
In 1996, Barbara, Gatteschi, and Sessoli, collaborating on studies
of single crystals of Mn12and Friedman, then a Ph.D. candidate
at City College of New York working independently with Mn12 powdersdiscovered
that the magnetic-moment reversal can occur at a smaller field in
a series of period steps. These steps can be explained by quantum
tunneling of magnetization (QTM). The discovery of QTM in Mn12 triggered
experiments on many magnetic molecules, which showed remarkable
quantum properties in a molecule called Fe8. The most spectacular
property was the existence of topological interference effects,
discovered by Wernsdorfer and Sessoli in 1999, which confirmed the
coherent character of the tunneling.
Although the scientists work is primarily of interest in
the field of quantum mesoscopic magnetism, their breakthrough may
also be important for future applications, the EPS noted.
The Forum department is initiated by the American Physical Societys
Forum on Industrial and Applied Physics (FIAP). For more information
about the Forum, please
visit the FIAP Web site or contact the chair, Gordon
A. Thomas .