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Revealing the infinitesimal

Researchers unlock the potential of the nano world

Half a century ago, the Nobel Prize-winning physicist Richard Feynman helped launch the era of nanotechnology when he told scientists to dream little, not big.

In an address to the American Physical Society, titled “There’s Plenty of Room at the Bottom,” Feynman told his audience they could develop tools capable of manipulating individual atoms and molecules.

Imagine putting a 24-volume encyclopedia on the head of a pin, Feynman said. Imagine 24 million books. Similarly scaled down, they could fit on 35 pages. What about computers? In 1959, they filled entire rooms. Why couldn’t they be made of wires just tens of atoms in diameter and circuits only a few hundred nanometers across?

Feynman did not talk of nanotechnology. A Japanese engineer, Norio Taniguchi, coined the term in 1974, and an American engineer, Eric Drexler, popularized it in 1986 with his book Engines of Creation: The Coming Era of Nanotechnology.

Self-assembly of microspheres (SiO2) and nanoparticles (polystyrene) for optical coatings.
AuPd nanoparticle on red TiO2 support, with palladium (green) at surface and gold (blue) at core.
A chemically etched silicon machine for mechanical testing of nanoscale materials.
An array of nanoholes (period: 100-300 nm) on a thin silver film with a filter function for nano plasmonic structures and potential for biosensing.

Fifty years after Feynman’s presentation, much of what he predicted has come to pass. Indeed, says Marvin White, consumers now demand a steady stream of miracle products with sizes – and price tags – locked in a never-ending downward spiral.

“Nano accounts for many major electronic advances of the past 10 years – cell phones, iPods, digital cameras, laptops, you name it,” says White, a member of the National Academy of Engineering and director of Lehigh’s Sherman Fairchild Center for Solid-State Studies.

“And there are applications of nano in almost every other field. Take waterproof clothing. Water runs off it because of nanoparticles embedded in the fabric. Look at health care. The response of cells to outside stimuli can be measured, and cell properties characterized, using nano research instruments.”

Nanotechnology has been defined as the engineering of systems with dimensions smaller than 100 nanometers. One nanometer (1 nm) equals one billionth of a meter or, as one wag put it, the length a man’s beard grows as he lifts his razor to his face.

White is one of more than 50 Lehigh faculty members involved in nano research. These engineers, physicists, chemists and biologists collaborate in a variety of groups and venues, including the Center for Advanced Materials and Nanotechnology (CAMN), which is well-equipped for nanocharacterization, and the Center for Optical Technologies (COT) and Sherman Fairchild Center, which have expertise in nanosynthesis and nanofabrication.

Lehigh’s nano researchers have scored successes in sensors and transducers, catalysts and sorbents, photovoltaics and light sources, nanoparticles and quantum-dot synthesis, and high-density information management. These are impacting energy, environment, infrastructure and other areas. Palladium-coated iron nanoparticles developed at Lehigh, for example, are treating contaminated groundwater in half a dozen states.

Lehigh’s bioengineering researchers also work at the nano level. Electrical engineers pursue nanophotonic biosensing on a chip. Physicists model the dynamics of the cell’s cytoskeleton. Materials scientists and mechanical engineers fabricate injection-molded nanostructures on which adult stem cells grow and differentiate.

An emphasis on the superficial
The key to nanotechnology research, says CAMN director Martin Harmer, is much what Richard Feynman envisioned – the control of molecules and atoms at the surfaces and interfaces that are a material’s most reactive regions.

“Our goal,” says Harmer, “is to equip surfaces and interfaces with desirable and predictable characteristics at the nanoscale. These include chemical composition and atomic structure, and structural, optical, conductive and magnetic properties.”

To understand the nano world, one must first observe it. Here, Lehigh offers an advantage: its surface analysis and microscopy tools are among the world’s best.

“Each apparatus we have integrates a number of analytical methods,” says Bruce Koel, vice president and associate provost for research and graduate studies. “This gives us a tremendously powerful, multitechnique approach to complicated problems.”

Lehigh’s scanning probe microscopes, both scanning tunneling (STM) and atomic force (AFM), characterize surface topography in every kind of medium. The university’s Scienta ESCA 300, one of 11 in the world and the only one in the U.S., is one of the best x-ray photoelectron spectroscopy (XPS) instruments available for chemical analysis. The high-sensitivity, low-energy ion-scattering spectrometer (HS-LEIS), under acquisition through a 2008 NSF grant, affords unprecedented surface analysis and will be the first instrument of its kind in an academic lab.

“The Scienta enables us to study surfaces with a high sensitivity and resolution for chemical analysis,” says Koel, a professor of chemistry. “It gives us information about the near surface – the chemical composition of the top 10 atomic layers of a material. If you see aluminum, HS-LEIS tells you whether it’s metal or oxide. If you see carbon, HS-LEIS tells you whether it is bound to oxygen or to another carbon.

“But the very top or outer layer, which measures just 0.2 to 0.3 nm in thickness, is critical for chemical behaviors. HS-LEIS uniquely tells us what the topmost layer of atoms is.”

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A metalorganic chemical vapor deposition reactor deposits nanostructures one atomic layer at a time on a semiconductor wafer.