Superconductive 2D germanium transistor

Developing on another element to the growing list of two-dimensional materials, researchers from the University of Twente in the Netherlands have demonstrated that germanene, a 2D material made of germanium atoms, can behave as a topological insulator – the first to consist of a single element – meaning it is comparable to transistors in that it can switch between on and off states for potentially more energy-efficient electronics.

Topological insulators are materials with the unique property of insulating electricity in their interior while conducting electricity along their edges. These conductive edges also allow electrical current to flow without energy loss – otherwise known as superconductivity.

"At the moment, electronic devices lose a lot of energy in the form of heat, because defects in the material increase the resistance," said UT researcher Pantelis Bampoulis. "As a result, your mobile phone can get uncomfortably hot."

While interruption at defects is expected and allowed in normal materials, at the edges of 2D topological insulators, the scattering of electrons at defects is prevented due to the unique topological protection mechanism. Therefore, electrical current in 2D topological insulators flows without dissipating energy, no loss.

This makes them more energy-efficient than traditional electronic materials such as silicone.

Germanene, much like graphene from graphite and MXenes from various elements like aluminum silicon, gallium, or aluminum carbide on ceramics, is a 2D material made up of a single layer of germanium atoms.

Created in a similar process to that of graphene or silicene, high-quality thin films of germanene have long revealed unusual two-dimensional structures with novel electronic properties suitable for semiconductor device applications and materials science research.

Discovered in 2014 after the initial breakthrough in graphene, then silicene, a 2D silicon material, germanene has sat quietly for a number of years as the understanding of 2D materials needed to catch up to the production of such products.

With breakthrough after breakthrough in the understanding of two-dimensional materials, potential uses are becoming almost too many to handle.

"Current topological insulators consist of complex structures from different types of elements," said Bampoulis. "Germanene is unique in that it's made from just a single element."

To create this exciting material, the researchers melted germanium together with platinum. When fully cooled, a tiny layer of germanium atoms arranged into a honeycomb lattice on top of the germanium-platinum alloy. This layer is what is called germanene.

The researchers also discovered that the conducting properties of the material can be switched off by applying an electric field, which is unique for a topological insulator.

"The possibility to switch between 'on' and 'off' states adds an exciting application case for germanene," added Bampoulis.

Not only does it pave the way for designing topological field-effect transistors, but these germanene transistors could also replace conventional silicon transistors in electronic devices, resulting in electronics that are supremely efficient.

This means they would no longer heat up, which ultimately degrades surrounding parts as well as extend the life of electronic devices for much greater than currently exhibited.