U.S. and Indian scientists have found a way to make atomically flat gallium more conducive for nanoscale electronics.
The Rice University Lab of materials scientist Pulickel Ajayan and colleagues from the Indian Institute of Science, Bangalore, created 2D gallenene, a thin film of conductive material that is to gallium what graphene is to carbon.
According to the team, gallium when extracted into a 2D form appears to have an affinity for binding with semiconductors like silicon and could make an efficient metal contact in two-dimensional electronic devices.
Known to have a low melting point, gallium – unlike graphene and many other 2D structures – cannot be grown via vapor phase deposition methods. It also has a tendency to oxidize quickly.
And while early samples of graphene were removed from graphite with adhesive tape, the bonds between gallium layers are too strong for such a simple approach.
So the Rice team led by co-authors Vidya Kochat, a former postdoctoral researcher at Rice, and Atanu Samanta, a student at the Indian Institute of Science, used heat instead of force.
Rather than a bottom-up approach, the researchers worked their way down from bulk gallium by heating it to 29.7 degrees Celsius (about 85 degrees Fahrenheit), just below the element’s melting point. According to the researchers, that was enough to drip gallium onto a glass slide.
As a drop cooled just a bit, the researchers pressed a flat piece of silicon dioxide on top to lift just a few flat layers of gallenene.
They successfully exfoliated gallenene onto other substrates, including gallium nitride, gallium arsenide, silicone and nickel. This allowed them to confirm that particular gallenene-substrate combinations have different electronic properties and to suggest that these properties can be tuned for applications.
“The current work utilizes the weak interfaces of solids and liquids to separate thin 2-D sheets of gallium,” said Chandra Sekhar Tiwary, principal investigator on the project. “The same method can be explored for other metals and compounds with low melting points.”
Gallenene’s plasmonic and other properties are also being investigated, reports Ajayan: “Near 2D metals are difficult to extract, since these are mostly high-strength, nonlayered structures, so gallenene is an exception that could bridge the need for metals in the 2D world.”
Image credit and content: Ajayan Research Group/Rice University