The Rice Lab of materials scientist Pulickel Ajayan and colleagues in India have created two dimensional gallenene, a thin film of conductive material that is to gallium what graphene is to carbon.
Extracted into a two-dimensional form, the novel material appears to have an affinity for binding with semiconductors like silicon and could make an efficient metal contact in two dimensional electronic devices, the researchers said.
Gallium is a metal with a low melting point; unlike graphene and many other two dimensional structures, it cannot yet be grown with vapour phase deposition methods. Moreover, gallium also has a tendency to oxidise 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. 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. That allowed them to confirm that particular gallenene-substrate combinations have different electronic properties and to suggest that these properties can be tuned for applications.