During the growth, the sharp edges of "trenches" cut into the silicon carbide become smoother as the material attempts to regain its flat surface. The growth time must therefore be carefully controlled to prevent the narrow silicon carbide features from melting too much.
The graphene fabrication also must be controlled along a specific direction so that the carbon atom lattice grows into the steps along the material's "armchair" direction. "It's like trying to bend a length of chain-link fence," Conrad explained. "It only wants to bend one way."
The new technique permits not only the creation of a bandgap in the material, but potentially also the fabrication of entire integrated circuits from graphene without the need for interfaces that introduce resistance. On either side of the semiconducting section of the graphene, the nanoribbons retain their metallic properties.
"We can make thousands of these trenches, and we can make them anywhere we want on the wafer," said Conrad. "This is more than just semiconducting graphene. The material at the bends is semiconducting, and it's attached to graphene continuously on both sides. It's basically a Shottky barrier junction."
By growing the graphene down one edge of the trench and then up the other side, the researchers could in theory produce two connected Shottky barriers a fundamental component of semiconductor devices. Conrad and his colleagues are now working to fabricate transistors based on their discovery.
Confirmation of the bandgap came from angle-resolved photoemission spectroscopy measurements made at the Synchrotron CNRS
|Contact: John Toon|
Georgia Institute of Technology Research News