Future Transistors: New Technique for Placing Graphene on Silicon


Graphene is the thinnest material that can be made out of atoms, yet it is very strong. Controlling whether or not it conducts by applying an electric field is a bonus. This cannot be done with metal because metal cannot be made thin enough to affect its conducting state.

Graphene-based transistors can run at higher frequencies and more efficiently than silicon transistors. Graphene has many uses, such as support membranes for transmission electron microscopy and in gas sensors because the effect of gas molecules that land on graphene are measureable.

Applied Physics Letters

Analog devices such as metal-semiconductor field effect transistors and high-electron mobility transistors benefit from graphene?s chemical and mechanical stability, its high electron mobility and great optical properties. Switching is obtained at metal-semiconductor (Schottky) junctions. Recent research by Sefaattin Tongay, Ph.D. and the University of Florida, supported by the Office of Naval Research and the National Science Foundation, was published by the American Institute of Physics.

That study indicated that temperature stability of high quality graphene/GaN Schottky diodes ?promises integration of graphene into high-performance analog devices operating at elevated temperatures.? The investigation used Raman Spectroscopy and temperature-dependent current-voltage measurements to determine rectification and thermal stability of diodes formed at graphene/GaN interfaces.

A simplified diagram of a Raman spectrometer?s operation. Credit: Cambridge University

A simplified diagram of a Raman spectrometer?s operation. Credit: Cambridge University

Now, Tongay and his teammates are looking into how to reliably manufacture graphene on a large scale. They developed a technique for creating graphene patterns on top of silicon carbide (SiC), a combination of silicon and carbon. The silicon atoms vaporize at about 1300 degrees Celsius whereby the carbon atoms grow into sheets of pure graphene. Previously, those sheets were etched into appropriate patterns, however the vary etching caused problems affecting the electron mobility.

Instead, the team implanted silicon or gold ions in SiC which lowered the temperature so that graphene formed around 100 degrees Celsius. By strategically placing the ions, then heating the SiC to 1200 degrees Celsius, the untreated areas did not form graphene, leaving nanoribbons of graphene where the ions had been placed. The article "Drawing graphene nanoribbons on SiC by ion implantation" is published in Applied Physics Letters.