New research suggests one-atom-thick graphene could pave the way for faster and more energy-efficient electronics.
In order to allow graphene to be used to its full potential in high-performance semiconductor electronics, scientists have been struggling to figure out a way to grow it into tiny strips called "nanoribbons," the University of Wisconsin-Madison reported. Now, researchers have created a way to grow graphene nanoribbons with desirable semiconducting properties directly on a conventional germanium semiconductor wafer.
This significant breakthrough could allow manufacturers to easily use graphene nanoribbons in hybrid integrated circuits, which would increase the performance of next-generation electronic devices. The new method could also allow graphene to be used in industrial and military fields, such as in lasers that detect specific chemicals.
"Graphene nanoribbons that can be grown directly on the surface of a semiconductor like germanium are more compatible with planar processing that's used in the semiconductor industry, and so there would be less of a barrier to integrating these really excellent materials into electronics in the future," said Michael Arnold, an associate professor of materials science and engineering at UW-Madison.
In order to take full advantage of graphene's remarkable electronic properties in semiconductor applications where current must be switched on and off, the nanoribbons must be less than a miniscule 10 nanometers wide and have well-defined "armchair" edges. In the past scientists have created nanoribbons using lithographic techniques to cut larger sheets of graphene into ribbons, but this method is not very precise. Another "bottom-up" approach called surface-assisted organic synthesis creates graphene nanoribbons by having molecular precursors react on a surface, but this method produces much shorter strands than would be useful in the desired fields.
To overcome these roadblocks, the researchers created a bottom-up technique in which they can grow perfect nanoribbons directly on germanium wafers through a process called chemical vapor deposition. In this method, the scientists use methane to absorb the germanium surface. Once this occurs, the methane decomposes to form a variety of hydrocarbons that react with each other on the surface to form graphene.
"What we've discovered is that when graphene grows on germanium, it naturally forms nanoribbons with these very smooth, armchair edges," Arnold said. "The widths can be very, very narrow and the lengths of the ribbons can be very long, so all the desirable features we want in graphene nanoribbons are happening automatically with this technique."
The findings were published in a recent edition of the journal Nature Communications.
