The researchers used this rack to stretch a layer of graphene in a controlled manner. Photo: Swiss Nanoscience Institute, University of Basel.The electronic properties of graphene can be specifically modified by stretching the material evenly, say researchers at the University of Basel in Switzerland. Their results open the door to the development of new types of electronic components.
Graphene consists of a single layer of carbon atoms arranged in a hexagonal lattice. The material is very flexible and has excellent electronic properties, making it attractive for use in numerous applications, particularly nanoscale electronic components.
Researchers led by Christian Schönenberger at the Swiss Nanoscience Institute and the Department of Physics at the University of Basel have now studied how graphene's electronic properties can be manipulated by mechanical stretching. In order to do this, they developed a kind of rack on which they can stretch an atomically thin layer of graphene in a controlled manner, while measuring its electronic properties.
The scientists first prepared a 'sandwich' comprising a layer of graphene between two layers of boron nitride. This stack of layers, furnished 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 enabled us to bend the stack in a controlled way, and to elongate the entire graphene layer," explained Lujun Wang at the University of Basel, who is lead author of a paper on this work in Communications Physics.
"Stretching the graphene allowed us to specifically change the distance between the carbon atoms, and thus their binding energy," added Andreas Baumgartner at the University of Basel, who supervised the study.
The researchers first calibrated the stretching of the graphene using optical methods. They then used electrical transport measurements to study how deformation of the graphene changes its electronic energies. These measurements need to be performed at -269°C for the energy changes to become visible.
"The distance between the atomic nuclei directly influences the properties of the electronic states in graphene," said Baumgartner. "With uniform stretching, only the electron velocity and energy can change. The energy change is essentially the 'scalar potential' predicted by theory, which we have now been able to demonstrate experimentally."
These results could lead 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 in recent years.
This story is adapted from material from the University of Basel, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.