In a new study published in Optica, researchers at the University of Colorado Boulder have used doughnut-shaped beams of light to take detailed images of objects too tiny to view with traditional microscopes.
The new technique could help scientists improve the inner workings of a range of "nanoelectronics," including the miniature semiconductors in computer chips. The discovery was also highlighted in a special issue of Optics & Photonics News.
The research is the latest advance in the field of ptychography, a difficult-to-pronounce (the "p" is silent) but powerful technique for viewing very small things. Unlike traditional microscopes, ptychography tools don't directly view small objects. Instead, they shine lasers at a target and then measure how the light scatters away—a bit like the microscopic equivalent of making shadow puppets on a wall.
So far, the approach has worked remarkably well, with one major exception, said study senior author and Distinguished Professor of physics Margaret Murnane.
"Until recently, it has completely failed for highly periodic samples or objects with a regularly repeating pattern," said Murnane, a fellow at JILA, a joint research institute of CU Boulder and the National Institute of Standards and Technology (NIST). "It's a problem because that includes a lot of nanoelectronics."
She noted that many important technologies, like some semiconductors, are made up of atoms like silicon or carbon joined together in regular patterns like a grid or mesh. To date, those structures have proved tricky for scientists to view up close using ptychography.
In the new study, however, Murnane and her colleagues devised a solution. Instead of using traditional lasers in their microscopes, they produced beams of extreme ultraviolet light in the shape of doughnuts.
The team's novel approach can collect accurate images of tiny and delicate structures that are roughly 10 to 100 nanometers in size or many times smaller than a millionth of an inch. In the future, the researchers expect to zoom in to view even smaller structures. The doughnut, or optical angular momentum, beams also won't harm tiny electronics in the process—as some existing imaging tools, like electron microscopes, sometimes can.
"In the future, this method could be used to inspect the polymers used to make and print semiconductors for defects without damaging those structures in the process," Murnane said.
To read more, click here.