Scientists create ultra-thin, cheap, flexible, transparent graphene semiconductors
By Ben Coxworth
September 28, 2012
Ordinarily, electronics are made with silicon semiconductors that are rigid, opaque, and about half a millimeter thick. Thanks to research being carried out at the Norwegian University of Science and Technology, however, that may be about to change. Led by Dr. Helge Weman and Prof. Bjørn-Ove Fimland, a team there has developed a method of making semiconductors out of graphene. At a thickness of just one micrometer, they are flexible and transparent. Also, because they require so little raw material, they should be considerably cheaper to manufacture than their silicon counterparts.
Graphene, for anyone who still doesn’t know, is a material made up of a one-atom thick sheet of hexagonally-linked carbon atoms. It is very electrically-conductive, inexpensive to produce, and is simultaneously the thinnest material in existence yet also one of the strongest.
To create the semiconductors, the Norwegian team starts by “bombing” a graphene substrate with gallium atoms, within a vacuum chamber. Those atoms stick to the graphene, and clump together with one another to form gallium droplets. On the underside of each droplet, where it meets the graphene, the gallium atoms naturally arrange themselves to match the hexagonal pattern of the graphene.
Next, arsenic molecules are also introduced to the graphene sheet, as the gallium atoms continue to rain down. Both arsenic molecules and gallium atoms are absorbed into the existing gallium droplets. Once inside a droplet, the arsenic travels to the bottom, where it combines with the gallium atoms. They form into a crystalline structure, on the bottom of the droplet.
As the process repeats itself, with countless other arsenic molecules entering the droplet and reacting with the gallium atoms on the bottom, the crystals accumulate to grow into a nanowire, with the droplet perched at the top. After just a few minutes, the hybrid finished product is ready – a graphene substrate covered with an array of one-micrometer-tall gallium/arsenic nanowires, evenly distributed in a hexagonal layout.
“A material comprising a pliable base that is also transparent opens up a world of opportunities, one we have barely touched the surface of,” said Dr. Weman. “This may bring about a revolution in the production of solar cells and LED components. Windows in traditional houses could double as solar panels or a TV screen. Mobile phone screens could be wrapped around the wrist like a watch. In short, the potential is tremendous.”
A spin-off company, CrayoNano, has been established to further develop the technology. Animation of the process can be seen in the video below.
Source: The Research Council of Norway