German researchers have developed a new method of graphene production, paving the way for wider use of the wonder material.
Described in the recent issue of the Advanced Materials journal, the method has been created by a joint team of the University of Bielefeld and the University of Ulm, Germany.
Using electron irradiation, the team has managed to create graphene layers covering large areas as well as very small, precise objects, thus enabling the production of graphene-based quantum dots, nanoribbons and other pre-defined nano-objects.
The technique also makes it possible to create multiple-layered graphene, which could offer improved electronic properties, further expanding its potential applications.
Conventionally, graphene is produced by depositing carbon atoms from a gas phase on a substrate or by thermal graphitisation of silicon carbide. However, the German team has focused on aromatic molecules instead, choosing conventional copper single-crystals and low-cost polycrystalline copper foils as substrates.
First, molecules of biphenyl thiol, an aromatic substance, are deposited on the substrate in a self-organised single layer. By irradiating the starting material with low-energy electrons and through subsequent thermal processing, the bipheyl thiol could be turned into a layer of graphene.
Graphene manufactured using the new technique has been put through advanced analytical testing, which has proved its outstanding crystalline and electronic properties
The new method allows using various aromatic molecules as the starting material and makes it possible to use doping atoms to further improve characteristics of the final product.
In addition to copper, other materials, including metals, semiconductors and isolators can be used as substrate for the graphene production. The starting molecules can also be deposited on three-dimensional surfaces.
By adjusting the temperature during the thermal conversion of the aromatic molecules, the researchers can change the degree of crystallinity – the level of structural order - and other characteristics of the produced graphene.
Graphene – a material composed of a single layer of carbon atoms arranged in a regular hexagonal structure – is believed to have the potential to bring about revolution in electronics, sensor technology or display technology.
The original preparation method used by Konstantin Novoselov and Andre Geim, who were awarded the Nobel Prize in Physics in 2010 for the discovery of graphene, relied on flaking of single atomic layers of graphite. However, this method was soon understood to be inefficient and not suitable for extensive technological use.
Developing sustainable procedure for industrial manufacturing of graphene is thus the goal of many researchers all over the world.