The scale of efforts around the development of graphene-based materials encourages the belief that graphene will evolve as a replacement to many existing material platforms. While this is not expected to happen over the next decade, it must be noted that various research groups are exploring the capabilities of graphene in a multitude of directions. These include the development of graphene-based transistors, graphene nanoplatelets for biosensing, understanding physical, structural and chemical properties of graphene, and manufacturing methods for graphene-based devices.
All of these efforts are distinct in their own sense and are contributing to the development of the graphene platform as a viable material solution for next-generation device requirements. Industrial opinions do however cite that there are manufacturing issues associated with graphene that need to be resolved before considering the incorporation of graphene-based devices in electronic systems. However, this has not deterred researchers from developing newer graphene-based devices.
Marking efforts in this direction, a team of researchers in Italy has created a graphene-based IC. By adapting a technique used to fabricate silicon transistors, the team created the device and then showed that it was capable of performing basic computational tasks.
In recent times, graphene-based transistors have been explored to a considerable extent by the research fraternity striving to make a mark in graphene electronics. A team at a noted university in the UK recently proved that it is possible to carve graphene into tiny electronic circuits with individual transistors having a size close to that of a molecule.
The nanoscale transistor built by the UK team was carved out of a graphene plane to form a single-electron (quantum dot) transistor. The two electrodes (source and drain) were connected by an island of conducting material or quantum dot that is only around 100 nm long. The width of the island was such that it accommodated only one electron at a time, while another electron is kept away by repulsion. An electron from the source tunnels quantum-mechanically to the island, then leaves by tunnelling on to the drain. The voltage applied to a third electrode, called the gate, controls whether a single electron can enter or exit the island, thereby registering either a 1 or a 0.
The current effort by the team at the Department of Physics from the Politecnico di Milano in Italy has been built upon one of the efforts in the United States, which made graphene transistors by fabricating nanoscale electrodes next to the surface of graphene to create a p-n junction. The Italian research group has used this as a basis and has strived to connect these transistors to make a basic IC.
In the process, the researchers first isolated an amount of graphene from a sheet of carbon using mechanical exfoliation – basically, ‘sticky tape’ – before depositing these onto a silicon substrate. Then, using high-resolution electron beam lithography, the researchers fabricated two p-type transistors on the same flake on graphene.
Having successfully developed a method to connect transistors, the team proceeded to check out the possibility of building a small inverter setup. This eventually called for a method to create an n-type transistor as well. To convert the p-type transistor into an n-type transistor, the team passed an electric current through one of the transistors and used the heating effect to remove contaminants. This converted one of the type p transistors to type n, resulting in an inverter setup. In order to demonstrate that they had created a very simple computing device, the researchers used the ‘circuit’ to perform the simple logic task of Boolean inversion.
For more information contact Patrick Cairns, Frost & Sullivan, +27 (0)21 680 3274, [email protected], www.frost.com
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