Prof. J. Fraser Stoddart, Northwestern University

Chemistry and Molecular Nanotechnology in Tomorrow's World

The development of molecular electronic devices (MEDs) for memory and logic applications in computing presents one of the most exciting contemporary challenges in nanoscience and nanotechnology. The lecture will highlight how the concepts of molecular recognition and self-assembly (template-directed synthesis) have been pursued actively during the production of two families of redox-controllable mechanically interlocked molecules - namely, bistable catenanes and bistable rotaxanes - which can be incorporated into a device setting in the form of a two-terminal molecular switch tunnel junction (MSTJ) wherein the bistable molecules can be switched electrically between high- and low-conductance states. In the case of a two-terminal MSTJ, the objective is to design and make a bistable molecule that, collectively in the device at a specific voltage, switches from a stable structure (isomer) to another metastable isomer with a different conductivity. The molecule needs to remain in the metastable state until either another voltage pulse is applied or thermal fluctuations cause a return to the starting state. The two states of the molecule correspond to the ON and OFF states of the switch and the finite stability of the metastable state leads to a hysteretic current/voltage response that forms the basis of the switch. Molecular random access memory (RAM) can be created by fabricating many MSTJs simultaneously into a crossbar type of architecture in a MED. The lecture will conclude with the description of a 160,000-bit molecular electronic memory circuit based on a bistable [2]rotaxane and fabricated at a density of 100,000,000,000 bits per square centimeter - that is, roughly analogous to the density of a DRAM circuit projected to be available by 2020. The entire 160,000-bit crossbar is smaller than the cross-section of a white blood cell.

For more information contact Rebecca Shaner.