The decidedly low-tech office supply stalwart Scotch Magic tape is at the heart of a new nano-manufacturing technique that could make electrical and optical devices smaller and more advanced than currently possible.
Specifically, by joining several standard nanofabrication techniques-and Scotch Magic tape-researchers at the University of Minnesota created extremely thin gaps through a layer of metal and patterned these tiny gaps over the entire surface of a four-inch silicon wafer. The smallest gaps were only one nanometer wide, much smaller than most researchers have been able to achieve.
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In addition, the widths of the gaps could be controlled on the atomic level. This work provides the basis for producing new and better nanostructures that are at the core of advanced electronic and optical devices, researchers said in a statement.
The researchers said that light could readily be squeezed through these gaps, even though the gaps are hundreds or even thousands of times smaller than the wavelength of the light used. The researchers said they are very interested in forcing light into small spaces because this is a way of boosting the intensity of the light. The collaborators found that the intensity inside the gaps is increased by as much as 600 million times.
The Scotch tape came into play when the research team was etching one-nanometer-wide gaps into metal. The researchers said they constructed the nano-gaps by layering atomic-scale thin films on the sides of metal patterns and then capping the structure with another metal layer. No expensive patterning tools were needed to form the gaps this way, but it was challenging to remove the excess metals on top and expose the tiny gaps. During a frustrating struggle of trying to find a way to remove the metal films, University of Minnesota Ph.D. student and lead author of the study Xiaoshu Chen found that by using simple Scotch Magic tape, the excess metals could be easily removed.
"Our technology, called atomic layer lithography, has the potential to create ultra-small sensors with increased sensitivity and also enable new and exciting experiments at the nanoscale like we've never been able to do before," said Sang-Hyun Oh, one of the lead researchers on the study and a professor of electrical and computer engineering in the University of Minnesota's College of Science and Engineering. "This research also provides the basis for future studies to improve electronic and photonic devices."
A research paper on the topic, "Atomic layer lithography of wafer-scale nanogap arrays for extreme confinement of electromagnetic waves," was published this week on the Nature Communications website.
The research was done by the University of Minnesota, Argonne National Laboratory and Seoul National University and funded by the U.S. Department of Defense (DARPA) the U.S. Department of Energy and the National Research Foundation of Korea with capital equipment funding from the Minnesota Partnership for Biotechnology and Medical Genomics.
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