Scientists get the drop on 2D gallium

Scientists at Rice University and the Indian Institute of Science in Bangalore have discovered a method for making atomically flat gallium that shows promise for nanoscale electronics. The Rice lab of materials scientist Pulickel Ajayan and colleagues in India have managed to create two-dimensional (2D) gallenene, a thin film of conductive material that is to gallium what graphene is to carbon.

Extracted into a 2D form, the novel material appears to have an affinity for binding with semiconductors like silicon and could make an efficient metal contact in 2D electronic devices, the researchers said. They describe the new material in a paper in Science Advances.

Gallium is a metal with a low melting point, but 2D versions cannot yet be grown using vapor phase deposition methods, unlike graphene and other 2D materials. Moreover, gallium 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 University, and Atanu Samanta, a student at the Indian Institute of Science, decided to use 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°C (about 85°F), just below the element's melting point. That was enough, however, to drip gallium onto a glass slide. As the drop cooled just a bit, the researchers pressed a flat piece of silicon dioxide on top, allowing them to lift off a few flat layers of gallenene.

With this technique, they successfully exfoliated gallenene onto other substrates, including gallium nitride, gallium arsenide, silicone and nickel. That allowed them to confirm that particular gallenene-substrate combinations have different electronic properties and to suggest that these properties could be tuned for applications.

"The current work utilizes the weak interfaces of solids and liquids to separate thin 2D sheets of gallium," said Chandra Sekhar Tiwary, principal investigator on the project, which he completed at Rice before becoming an assistant professor at the Indian Institute of Technology in Gandhinagar. "The same method can be explored for other metals and compounds with low melting points."

According to Ajayan, gallenene's plasmonic and other properties are currently being investigated. "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," he said.

This story is adapted from material from Rice University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.