The prospect for quantum-interference-controlled molecular electronics utilizing graphene nanoribbons

December 8, 2010 - In the recent Physical Review Letters article, Prof. Nikolic and postdoctoral researcher Dr. Kamal K. Saha  have proposed a new type of molecular-scale devices where a single ring-shaped organic molecule is connected to electrodes made of graphene nanoribbons (see illustration on the right). Molecular electronics is the subfield of nanoscience that investigates the electronic and thermal transport properties of circuits in which individual molecules (or an assembly of them) are used as basic building blocks.

According to the analysis presented in the article, the usage of nanometer-wide wires made of recently discovered two-dimensional crystal of carbon atoms termed graphene, for which Nobel Prize in Physics 2010 was awarded, has the capability to resolve one of the key challenges for molecular electronics - a well-defined molecule-electrode contact with high transparency, strong directionality, and reproducibility.

In recent years, molecular electronics has emerged as a playground where basic quantum phenomena can be probed via macroscopic transport measurements at room temperature. For example, quantum interference effects in electron propagation through molecular rings provide a realization of the two-slit experiment (with each semi-circle acting as one of the slits) from the textbook quantum mechanics. Moreover, unlike in mesoscopic rings patterned in conventional two-dimensional electron gases or graphene, such phenomena can manifest even at room temperature since molecular vibrations with dephasing effect can be suppressed below 500 K.

The proposed molecular transistor controlled by quantum interference effects is expected to operate with greatly reduced heat dissipation, which is the major obstacle for increasing speed of the present silicon-based electronics. This is because of the fact  that the current flow in the envisaged device is not blocked by an energy barrier as in traditional field-effect transistors where it must be raised and lowered with each switching cycle.

The theoretical prediction of Nikolic group relies on sophisticated first-principles quantum transport simulations that were conducted through massively parallel runs (consuming about 500,000 hours) on one of the fastest supercomputers in the world, TACC Ranger operated by the NSF TeraGrid. For more information about theoretical and computational research on nanoelectronics and quantum transport at the University of Delaware see graphene nanoelectronics page on the DPA Website.