H-BN looks like graphene, with the same chicken-wire atomic array. The earlier work at Rice showed that merging graphene and h-BN via chemical vapor deposition (CVD) created sheets with pools of the two that afforded some control of the material's electronic properties. Ajayan said at the time that the creation offered "a great playground for materials scientists."
He has since concluded that the area of two-dimensional materials beyond graphene "has grown significantly and will play out as one of the key exciting materials in the near future."
His prediction bears fruit in the new work, in which finely detailed patterns of graphene are laced into gaps created in sheets of h-BN. Combs, bars, concentric rings and even microscopic Rice Owls were laid down through a lithographic process. The interface between elements, seen clearly in scanning transmission electron microscope images taken at Oak Ridge National Laboratories, shows a razor-sharp transition from graphene to h-BN along a subnanometer line.
"This is not a simple quilt," Lou said. "It's very precisely engineered. We can control the domain sizes and the domain shapes, both of which are necessary to make electronic devices."
The new technique also began with CVD. Lead author Zheng Liu, a Rice research scientist, and his colleagues first laid down a sheet of h-BN. Laser-cut photoresistant masks were placed over the h-BN, and exposed material was etched away with argon gas. (A focused ion beam system was later used to create even finer patterns, down to 100-nanometer resolution, without masks.) After the masks were washed away, graphene was grown via CVD in the open spaces, where it bonded edge-to-edge with the h-BN. The hybrid layer could then be picked up and placed on any substrate.
While there's much work ahead to characterize the atomic bonds w
|Contact: David Ruth|