05-03-2021 | | By Robin Mitchell
Researchers from the University of Sussex have discovered how to manipulate single graphene sheets to create transistor-like components. Why is graphene a good candidate for next-generation devices? What have the researchers demonstrated, and is it a viable method for creating electronic devices?
All electronic components currently developed rely on the use of materials with 3D structures. For example, semiconductors are made using crystalline semiconductor materials such as Silicon and Germanium that have both height, width, and depth.
However, Graphene is often regarded as a 2D structure because the material is only one atom in height. This means that all current flow happens on the structure's plane with electrons not being able to travel vertically.
The atomic structure of graphene results in quantum effects that create extremely interesting properties including electron flow behaving like a viscous fluid. Furthermore, graphene structure creates a strong material (strongest currently known to man), with excellent thermal transfer properties, more conductive than copper and silicon, and ability to be used as a semiconductor.
The atomic size of graphene leads to creating transistors hundreds of times smaller than ones currently being developed. The reduction of transistor size reduces energy consumption per device, increases the overall number of transistor on a single device. The thermal properties allow for higher frequency operation (as it can readily remove heat generated).
Recently, researchers from the University of Sussex have discovered and demonstrated that graphene, when folded, can produce interesting electrical properties that may be exploitable to produce electronic devices.
According to the researchers, graphene layers can be made to have kinks using atomic force microscopy. Changes to the structure that the researchers achieved include standing collapsed wrinkles, folded wrinkles, and adding grain boundaries.
Once folded, the researchers noticed that graphene's band structure changed (i.e. the energy difference between electrons in valence and conductive bands). In wrinkled graphene, the bandgap changes were minimal, but the creation of edges in graphene resulted in major doping.
The major discovery in the tests is that a graphene device would not require doping of different materials (such as boron and phosphorus) to create devices. Instead, simple manipulation of a single sheet can be enough to create logic devices.
The folding of graphene sheets to create devices is promising from the perspective of needed compounds and materials. The fewer chemicals needed to create a semiconductor are generally better for the environment, and carbon being abundantly available could see production simplified from a supply chain point of view.
However, mechanically manipulating graphene could be a challenging task. Current production methods use lithography whereby light is passed through a mask, and an entire chip is patterned in one stage.
A mechanical method, however, may require each transistor to be physically produced. Thus, such a device may not be practical to produce in scale.
Of course, this could change if researchers can find a way to introduce distortions and folds into graphene using light and a mask in a near-identical method to lithography. However, lithography already faces issues, and using light to adjust graphene sheets may not be possible (commercially at least).
Thus, if folded graphene is to be the answer to the next generation of electronics, researchers will need to find a way of being able to manipulate 1 billion devices simultaneously.