A schematic showing a microscope measurement where a pulse of laser light illuminates a needle positioned above the sample surface. The gold is on top of the Graphene. The distribution of electrons is shown in the data. Credit: Spencer Ammerman
Tyler Cocker had a clear goal when he joined Michigan State University: to build a powerful microscope that would be the first of its kind in the United States.
It was time to use the microscope.
Cocker is the Jerry Cowen Endowed Chair in Experimental Physics in the College of Natural Science's Department of Physics and Astronomy. We have the best microscope in the country. We should use this to our advantage.
Cocker's team uses light and electrons to study materials with an unparalleled intimacy and resolution. The building blocks of quantum computers and next-generation solar cells can be seen and measured by the researchers.
The first glimpse of those capabilities was given in the journal Nature Communications, where the team took snapshots of how electrons are distributed.
Cocker said that this type of microscope can tell you something new. We're very proud of the work. We have a lot of ideas about where we want to go with it.
Cocker's team is part of a collaboration that is working to develop theseribbons into qubits for quantum computers. A grant from the Office of Naval Research will provide more than $1 million for the collaboration, which spans five institutions.
Cocker collaborated with the research group of Roman Fasel, a professor at the Swiss Federal Laboratories for Materials Science and Technology. The bottom-up growth method is what Fasel invented. With the addition of heat, the lab has created a molecule that can be made into ribbons with a certain shape and size.
"You bake the molecule like a cake," Cocker said. The properties of the ribbon are preset. You know what you're getting.
An illustration shows a gold surface. The data is shown in blue above the ribbons. Credit: Spencer Ammerman
Cocker's lab grew the ribbons and then examined them with a microscope after the Swiss lab sent the molecule. The basis for the instrument is a scanning tunneling microscope that brings a very sharp tip or probe close to the specimen being studied without touching it.
Even though the tip and sample are not in contact, electrons can still jump from the tip to the sample. The microscope builds high-resolution images of the sample and its properties by recording how the electrons tunnel.
Cocker and his team have done a great job with the combination of the conventional STM and laser light, which allows them to bring the tip closer to the sample. They're able to get more detailed information from a sample.
He said it was almost like we were zooming in by physically bringing the tip closer.
The team was able to show how electrons are distributed within the structure with atomic resolution.
This work has earned awards for its authors. A post-doc won an award for his poster at a recent workshop in Germany. Spencer Ammerman won an award for presenting his work at a conference hosted by the Infrared, Millimeter and Terahertz Wave Society.
Cocker and his team are excited about the new paper, but they are also looking forward to what's next. The team is working on showing how electrons move within the ribbons as the material absorbs light.
The only two microscopes like this in the U.S. will both be at Michigan State, thanks to a Department of Defense grant awarded in June.
"This paper is exciting, but it's just the first step," Cocker said. "We think it will open up a lot of possibilities."
More information is available in Nature Communications. There is a DOI: 10.1038/s41467-021-26656-3.
Nature Communications is a journal.
The light wave-driven scanning tunneling-spectroscopy of atomically precise graphene nanoribbons was retrieved on November 24, 2021.
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