Stretching alters the electronic properties of graphene
(Nanowerk News) The electronic properties of graphene can be specifically changed by stretching the material evenly, according to researchers at the University of Basel. These results (Communications physics, “Stress-induced global scalar potential in graphene devices”) open the door to the development of new types of electronic components.
Graphene is made up of a single layer of carbon atoms arranged in a hexagonal lattice. The material is very flexible and has excellent electronic properties, which makes it attractive for many applications – electronic components in particular.
Researchers led by Professor Christian Schönenberger of the Swiss Institute for Nanoscience and the Department of Physics at the University of Basel have now investigated how the electronic properties of the material can be manipulated by mechanical stretching. To do this, they developed a kind of rack by which they stretch the atomically thin layer of graphene in a controlled manner, while measuring its electronic properties.
Sandwiches on the rack
Scientists first prepared a “sandwich” comprising a layer of graphene between two layers of boron nitride. This stack of layers, provided with electrical contacts, was placed on a flexible substrate.
The researchers then applied a force to the center of the sandwich from below using a wedge. “This allowed us to bend the stack in a controlled manner and lengthen the entire graphene layer,” explained lead author Dr Lujun Wang.
“Stretching of graphene allowed us to specifically alter the distance between carbon atoms, and therefore their binding energy,” added Dr Andreas Baumgartner, who oversaw the experiment.
Modified electronic states
The researchers first calibrated the stretch of graphene using optical methods. They then used electrical transport measurements to study how the deformation of graphene changes electronic energies. Measurements should be made at minus 269 ° C for energy changes to become visible.
“The distance between atomic nuclei directly influences the properties of the electronic states of graphene,” said Baumgartner, summarizing the results. “With uniform stretching, only the speed and energy of the electrons can change. The energy change is essentially the theoretically predicted “scalar potential”, which we have now been able to demonstrate experimentally. ”
These results could lead, for example, to the development of new sensors or new types of transistors. In addition, graphene serves as a model system for other two-dimensional materials which have become an important research topic around the world in recent years.