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Published June 15, 2007 | public
Journal Article

Designing bistable [2]rotaxanes for molecular electronic devices


The development of molecular electronic components has been accelerated by the promise of increased circuit densities and reduced power consumption. Bistable rotaxanes have been assembled into nanowire crossbar devices, where they may be switched between low- and high-conductivity states, forming the basis for a molecular memory. These memory devices have been scaled to densities of 10¹¹ bits cm⁻², the 2020 node for memory of the International Technology Roadmap for Semiconductors. Investigations of the kinetics and thermodynamics associated with the electromechanical switching processes of several bistable [2]rotaxane derivatives in solution, self-assembled monolayers on gold, polymer electrolyte gels and in molecular switch tunnel junction devices are consistent with a single, universal switching mechanism whose speed is dependent largely on the environment, as well as on the structure of the switching molecule. X-ray reflectometry studies of the bistable rotaxanes assembled into Langmuir monolayers also lend support to an oxidatively driven mechanical switching process. Structural information obtained from Fourier transform reflection absorption infrared spectroscopy of rotaxane monolayers taken before and after evaporation of a Ti top electrode confirmed that the functionality responsible for switching is not affected by the metal deposition process. All the considerable experimental data, taken together with detailed computational work, support the hypothesis that the tunnelling current hysteresis, which forms the basis of memory operation, is a direct result of the electromechanical switching of the bistable rotaxanes.

Additional Information

© 2007 The Royal Society. Published online 12/04/2007; Published in print 15/06/2007. Discussion Meeting Issue 'Supramolecular nanotechnology for organic electronics' organized by Franco Cacialli, Harry L. Anderson and Richard H. Friend. The authors acknowledge the many stimulating discussions and intellectual contributions of our former and current colleagues whose names appear in the references. This research has been supported by grants from the Defense Advanced Research Projects Agency (DARPA) and both the Functional Engineered Nano Architectonics (FENA) Focus Center and the Center for Advanced Materials and Devices within the Microelectronics Advanced Research Corporation (MARCO).

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