Everything is constructed of atoms. Everything. An atom is the smallest unit of matter that can exist and still have the properties of its own elemental substance. These fundamental specks—packed with energy from charged subparts—are the building blocks of all matter. Each atom is a whirling mix of space, with a core of even tinier bits of protons and neutrons surrounded by a cloud of electrons, all held together by electromagnetic forces. Atoms connect, through chemical bonds, to form molecules, elements, and compounds in a vast array of ingeniously different patterns and structures. The results produce liquids, gases, metals, stone, water, wood, fish, bugs, plants, animals, planets, stars, and, yes, humans. Scientists have been aware of such elemental forces for centuries, but they have only been able to “see” and manipulate matter at the atomic level for roughly 100 years. Pitt physicist Jeremy Levy is part of a new breed of scientists who routinely work at the scale of individual atoms, trying to understand and control the forces that are packed into this mighty but minuscule realm. Usually, his workspace is far smaller than the head of a straight pin.
Two summers ago, Levy was in Germany visiting Jochen Mannhart, a colleague at the University of Augsburg. Mannhart, an expert in experimental physics, was exploring the properties of new materials for advanced electronic and computer technologies. His research team had discovered something interesting, and Levy—a professor of physics—considered how the results might apply to his own research at the University of Pittsburgh.
The German team had been experimenting with oxides, chemical compounds that form naturally on the surface of most metals. The researchers placed two different layers of oxides together. Separately, neither of these materials conducted electricity; but, when placed together, the two oxides created an interface that became an electrical conductor. Even more surprising, the researchers discovered they could switch the conduction on and off, like a light switch, by applying positive (on) or negative (off) voltage from a battery.
Instantly, says Levy, the experiment made him think of Etch A Sketch,®a children’s drawing toy that lets users dial knobs back and forth to produce lines on a display screen—and erase them—to create patterns, doodles, and sketches. Draw. Erase. On. Off.
An optical beam splitter cube.
He wondered, could he draw a current-carrying structure onto the material? Could he draw “wires”? More importantly for his research, could he draw them at the scale of atoms?
The on-off switching property in the German research likely results from the rearrangement of atoms near the interface of the two oxides, stimulated by the zap of charge. The charge attracts or repels atomic particles, resulting in the loss or gain of an atom’s electrons, which creates a different chemical structure. In one state, the material is a conductor. Then, zapped with negative voltage, the material changes its state to an insulator.
These interactions are nothing new. They’re based on ordinary chemistry and physics, with atoms being moved about, connected, and rearranged within an electromagnetic field that influences everything. It’s the arrangement and rearrangement of atoms that creates everyday chemicals and molecules.
What’s different today is that scientists are increasingly able to enter deeper and deeper into the world of atoms, exploring their properties and subparts and manipulating them to create whole new substances. That’s what is happening in nanotechnology, which is an evolving field that combines science, engineering, and manufacturing. Nano is from the Greek word that means “dwarf.” A nanometer is a metric system measurement for one-billionth of a meter; and about three to six atoms can fit into a single nanometer, depending on the size of the atom. The width of an average human hair is about 100,000 nanometers.
Inventions at the nanoscale will create products, methods of discovery, and modes of manufacture that are, without exaggeration, revolutionary—different from and more effective than anything yet in existence. The future of nanotechnology may produce a substance lighter than steel but 100 times stronger, or material that shifts from hard to soft with the click of a computer mouse, or teensy robots that deliver drugs to cancer cells.
At the moment, nanoscale applications are more basic but still exciting. For instance, at the University of Pittsburgh, faculty researchers from many disciplines across campus are collaborating through Pitt’s Gertrude E. and John M. Petersen Institute of Nanoscience and Engineering. The institute—which was ranked second in the nation in 2006 for micro- and nanoresearch by the trade publication Small Times—houses advanced equipment to enable discoveries at the extremes of nanomeasurement.
Some Pitt scientists are harnessing the power of light to create new energy sources; some are working to develop synthetic blood cells; some are developing shimmering indestructible industrial coatings; some are producing highly sensitive medical and chemical sensors; some are exploring molecular-size manufacturing tools. And some, like Levy, are working to launch a new era in computing and science.
Reflecting that the world of physics is full of surprises,
Levy poses suspended above two hardworking graduate
students, Yanjun Ma (left) and Patrick Irvin (right).
“When I saw Mannhart’s results,” says Levy, “I immediately began thinking about how it might be transferable to the nanoscale.” In nanoscience, there’s a natural inclination to take an existing process at the millimeter or micro level and see how it translates, how it behaves, on an extremely small scale. The German team was working with materials that can be measured in millimeters. Levy decided to try something similar in the nanoworld.
He began to experiment with materials supplied by Mannhart, but Levy’s work environment was about a billion times smaller than the one in Germany.
Nanoscientists use ever-more-sophisticated equipment to help them visualize surfaces and forces that reveal the presence and position of atoms—bumps on a surface; particles caught in light; waves that bounce or turn unexpectedly, suggesting unseen objects. The tools include laser-based probes and specialized microscopes equipped with supersharp tips that can gauge various properties with atomic precision to measure things like magnetic force, friction, light absorption, and even height. Visual maps are generated from this information.
In the Pitt experiment, Levy and his team of graduate students used an atomic force microscope, dragging its sharp tip across an oxide layer to interact with atoms. Then, the Pitt team applied a positive voltage charge from the microscope’s tip. That zap created a conductive dot underneath the tip just below the material’s surface. Then, the researchers discovered they could “erase” the teeny conductive dot by applying a negative voltage charge through the tip at the same location, rendering the spot nonconductive. On. Off. Draw. Erase. From this, and inspired by Etch A Sketch,® Levy realized that it should be possible to “draw” nanosize wires, creating powerful circuit elements at extreme nanoscale dimensions.
“If we want to ‘write’ a wire,” says Levy, “we apply a positive voltage charge and move the tip from Point A to Point B. If we want to ‘cut’ the wire, we apply a negative voltage to the tip, scan across the wire, and snip it.”
Going beyond the German experiment, which involved on-off control of conduction over an entire surface, Levy’s team localized the effect to individual nanodots.
While other scientists, globally, are working on various approaches to nanoelectronics, Levy’s breakthrough confirms that it’s feasible to create circuitry at an extreme nanoscale. It’s also feasible to control and modify such circuitry simply by redrawing it—all at room temperature, which is essential for future everyday applications in homes and offices. Potential implications include increased efficiencies in today’s electronic and computing devices, as well as future developments in nanoscale power devices, like improved memory-storage components with more information capacity in less space.
“There is a discovery-oriented element to all of this. We want to demonstrate that certain things are possible,” says Levy, who has been on the Pitt faculty since 1996. And Levy is not just a researcher, he’s also a teacher of both graduate and undergraduate students. His ideas and methods are being shared with a new generation of scientists. In recent years, he won Chancellor’s Awards for excellence and innovation in both his research and his teaching.
Levy earned a bachelor’s degree in physics at Harvard and a PhD degree at the University of California at Santa Barbara. Mathematics and science were childhood interests, but he focused on acting during his youth in New York City. His film credits include several Hollywood-studio movies. Even so, his father, Edmond Levy—an Academy-Award winning documentary filmmaker—encouraged him to pursue other career paths. So, in his mid-teens, Levy began spending summers working in laboratories. “That was something I always liked to do,” says Levy, “and I was naturally drawn to physics.”
Developments in modern physics, spanning roughly the past 100 years, have led to a new framework for understanding the fundamental laws of nature. That framework is quantum mechanics, which aims to decipher the physical principles that govern the universe from the level of atoms to galaxies. Physicists continue to grapple with how elemental particles and forces behave intrinsically and in relation to one another. Discoveries in quantum mechanics will help to explain the universe far more comprehensively than Newton’s laws ever could.
During 1993-95 postdoctoral studies at the University of California, Santa Barbara, Levy began to focus on electrons, the negatively charged bits within atoms, and investigate how they’re influenced by magnetic fields. This led him to explore characteristics of an electron’s spin. Like many other things in the quantum world, “spin” is more than it seems. An electron can be thought of as spinning about its own axis like a gyroscope. Each electron can spin clockwise, counterclockwise, or both directions at the same time. “This is very strange and counterintuitive, but it’s fundamental to quantum mechanics,” says Levy.
he electron’s multistate spin may be key to crossing a new frontier in computing. Some of Levy’s work at the University of Pittsburgh seeks to harness the strangeness of quantum behavior and, perhaps, combine it with other research pursuits, like his nanocircuitry work.
Today’s traditional computers use switching and logic circuitry built upon memory elements that can exist in two basic states; for instance, on or off, yes or no, true or false. This control element is used as a gate to direct logic functions. If “yes,” then X happens; if “no” then Y happens. Data bits are transmitted and stored based on the binary number system, where only two digits—1 and 0—are compiled in long, complicated code-combinations to represent numbers and letters. This system is the foundation for all data calculation, and “bits” are the basic unit of information processing.
To find an analogy for a computer bit in the quantum world, Levy is targeting electrons. The electron’s multispin direction can be used to represent a 1 state (clockwise), a 0 state (counterclockwise), and a “superposition” of all possible states between 1 and 0 (clockwise and counterclockwise simultaneously).
“What we’re trying to do,” he says, “is to make a quantum bit that could be used inside a quantum computer.” A quantum bit, or qubit, would take advantage of the electron’s multistate spin power; and a quantum computer would be capable of magnitudes-of-order more calculating power.
If Levy and his research team can harness the spectrum of energy in an electron’s spin-states, that breakthrough could lead to a radically new way to carry, store, and manipulate data and to conduct exponentially more calculations.
There are, of course, plenty of obstacles. “Exquisite control at the atomic scale is needed to make these computations work properly,” says Levy. “The amount of ordinary computer memory that’s required to represent a quantum mechanical state grows exponentially with the number of particles involved. That’s why it’s so difficult to simulate, using ordinary computers, the quantum-mechanical world around us.” Building a quantum computer, says Levy, would offer new hope in solving otherwise intractable problems in science and technology.
The challenges are so daunting that ultimate success may not come with this generation of scientists. But there is some urgency. If quantum computing ever becomes a reality, it will quickly unravel all encryption schemes used to protect secure transactions—like credit card purchases—on the internet. A quantum computer would be able to decode virtually any internet transmission, including military communications.
Levy recently received $1 million in funding as part of a national $6 million Multi University Research Initiative or MURI to explore new approaches to—and uses for—electron spin, known as spintronics. His work is just one aspect of what it will take to build a quantum computer, but the possibilities for groundbreaking discoveries in computing and physics are many.
Already, through more traditional nanoscale research, Levy and his Pitt team are experimenting to capture electrons in various surface materials. Along the way, they’re inventing new materials and new tools to help in their quest.
On. Off. Draw. Erase. Jeremy Levy continues to look closer.
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