Voltage at nanoscale: Leiden researchers win NeVac prize
Jaap Kautz and Johannes Jobst have won the NeVac prize for developing a completely new method for studying electrical conductivity. The article they and their team leader Sense Jan van der Molen wrote about this subject was praised by the jury for its clarity. The prize will be presented to them on NeVac-day, 17 April 2015, in Groningen.
Physicists are currently engaged in developing a revolutionary type of material: material with properties that can be pre-programmed. The inspiration for this development is graphene: a flat type of material, the layer of which has a thickness of exactly one single atom. But graphene is not unique: there are other ‘two-dimensional’ materials. A completely new material can now be developed by carefully building up a stack of different layers of this type. The properties of such ‘van-der-Waals’ systems are determined by the choice and sequence of their layers. You can compare this with building with Lego blocks: you can create a completely new structure by adding single blocks.
A new measuring method
Further research is needed in order to optimise the use of these new types of materials. It is important to test a new material for such properties as electric conductivity and insulation. Jaap and Johannes have developed a new measuring method to test these properties. They use a particular electron microscope, called a low-energy electron microscope that makes images using relatively slow-moving electrons. Because the electrons move so slowly, their chance of reflection is strongly affected by local voltage in a material.
The researchers have managed to measure exactly how the electric currents flow through the material. In particular, they have been able to demonstrate that the conductivity of graphene depends on the stacking of the exact number of layers.
The ‘van-der-Waal’ materials represent a promising system for new applications. Due to the new Leiden measuring method, researchers are now able to identify quickly and accurately the relation between properties of materials and the specific stacking of layers. The Dutch Vacuum Society (NeVac) has awarded the researchers the annual NeVac prize for their work.
Photo: Jaap Kautz standing behind his apparatus. The prize-winning research was carried out using a particular type of microscope: a low-energy electron microscope (LEEM).