Small is different
Silicone is the magic material that helps facilitate the electrical currents in modern semiconductors and powers many of the devices of everyday life, such as computers, radios, and telephones.
But Columbia Physicist Philip Kim is working with microscopic materials in which electrons move more than 100 times faster than in silicone—and have the potential to revolutionize electronics.
Kim, a professor of Physics and member of the Nanoscale Science and Engineering Center, is studying cutting edge materials on the nanometer scale that, because of their dimensions and physical characteristics, have unique electrical and thermal properties. These materials are so thin, that they are considered to have only one or two dimensions.
When “dimensions are smaller,” Kim says, “electrons behave differently—quantum mechanics kick in and creates exotic physical phenomena that allow for an ultrafast transistor.”
“From the very beginning we have speculated these materials have many potential applications,” Kim says. “Now it can be assumed they will have an impact, especially with conventional electronic device applications.”
Kim has made many contributions to the burgeoning field of nanoscience. A native of Seoul, he arrived in the United States for graduate and post-doc work just as physicists were beginning to grapple with the potential of nanoscale technologies.
During his PhD and postdoc work at Harvard and then post-doc work at Berkeley, Kim focused on carbon nanotubes, cylindrical carbon molecules that can run several centimeters in length but are about 50,000 times smaller than the width of a human hair. These microscopic tubules are extraordinarily strong. And since the electrons that move through them are deprived of two other dimensions that would allow them to bounce back, they exhibit unique electric and thermal properties. Kim speculated, and then demonstrated that they can be a good metal or semiconductor and could conduct heat as well as a diamonds.
At Columbia, he continued to examine the thermal and electrical properties of nanotubes, and explored ways that they could be combined with single molecules.
“We showed nanotubes have interesting thermal electrical properties that can have applications for clean energy and also typically electronic device applications,” he said.
Kim and his colleagues at the Nanoscale Science and Engineering Center were also among the first groups in the world to study graphene, one-atom-thick sheets of carbon that are perhaps the thinnest material in the universe. Graphene is closely related to nanotubes—which are essentially graphene folded into a cylinder. And graphene exhibits many of the same properties as nanotubes, but is easier to manipulate.
No graphene exists in a natural state. So, in his lab, Kim developed a device he called a “nanopencil,” capable of cleaving flakes of graphene from a graphite crystal. Kim and his colleagues also demonstrated that a phenomenon known as the “quantum Hall effect,” can occur in grapheme at room temperatures, instead of at very low temperatures required to create the effect in semiconductors.
Meanwhile, he’s continued to explore ways to combine nanotubes with single molecules.
“The nanotube is the ideal electrical contact,” he says. “And of course, a single molecular is the smallest transistor you can form, so you can create smallest transistor in combination with nanotube and single molecule that is extremely fast.”
To view technologies from Philip Kim's lab, please click here