Apr 21 2015
Researchers from Yale-NUS College, the University of Texas at Austin (UT Austin), and from the National University of Singapore (NUS), have collaborated in a study to establish a theoretical framework for understanding the physics of graphene.
Graphene was discovered around ten years back, and since that time, researchers have been studying different methods for engineering electronic band gaps in graphene, with the aim of helping to produce semiconductors that could be used in the creation of new electronic devices.
Graphene is a simple material that has unrivalled electronic and mechanical properties. Comprising of a single-atom-thick sheet of carbon atoms arranged in the form of a honeycomb-like lattice, it is lightweight, strong, and a very good conductor of electrons.
Researchers from the Massachusetts Institute of Technology had, in 2013, discovered that when graphene was placed on top of hexagonal boron nitride, it led to the creation of a hybrid material that possessed the electron conducting ability of graphene, along with the necessary band gap that was required for formation of semiconductor devices. Hexagonal boron nitride is a material that is similar to graphene. It is also just one atom thick, and shares some properties.
Semiconductors play an important role in modern electronics. They have the ability to switch between insulating and conducting states. The reasons behind the performance of this hybrid material was not known until this new theoretical framework was established.
The properties of the hybrid material have to be fully harnessed in order to create feasible semiconductors. For this, it is essential that a robust band gap that does not have any degradation in its electronic properties is available. The team of researchers determined that a theoretical framework that treated both the mechanical and electronic properties equally had to be applied, so that reliable predictions could be made about the new hybrid materials.
Shaffique Adam, Assistant Professor at Yale-NUS College and NUS Department of Physics, said, "This theoretical framework is the first of its kind and can be generally applied to various two dimensional materials. Prior to our work, it was commonly assumed that when one 2D material is placed on top of another, they each remain planar and rigid,"
"Our work showed that their electronic coupling induces significant mechanical strain, stretching and shrinking bonds in three dimensions, and that these distortions change the electronic properties. We find that the band gap depends on several factors including the angle between the two sheets and their mechanical stiffness. Going forward, we will continue to theoretically explore the optimal parameters to create larger bandgaps that can be used for a wide range of technologies."
Pablo Jarillo-Herrero, the Mitsui Career Development Associate Professor of Physics at MIT, whose research team first reported band gaps in this new graphene hybrid material, said, "This theory work has increased the accuracy and predictability of calculating the induced band gap in graphene, which may enable applications of graphene in digital electronics and optoelectronics. If we are able to increase the magnitude of the band gap through new research, this could pave the way to novel flexible and wearable nanoelectronic and optoelectronic devices."
Researchers from the Department of Physics and the Center for Advanced 2D Materials at NUS had taken part in this study.
The Ministry of Education and the National Research Foundation have funded the research conducted in Singapore.
The findings of this study have been published in the journal, Nature Communications.