Molecular switch junctions in silicon-organic molecule interface
D. Nozaki, C. Toher, F. Pump, and G. Cuniberti
Max Bergmann Symposium 2008
2008.11.04-06; Max Bergmann Center, Dresden, Germany
Since the success of the measurement of current conduction through individual molecules, molecular electronics has achieved a series of significant advances. Recently the integration of nanotechnology with biological systems has created the opportunity to use bio-recognition for the development of molecule-based devices such as sensitive bio-sensors. In particular, the silicon-organic molecule interface provides a promising platform for the development of such bio-molecule-based molecular devices. I this work, we explore the usability of organic molecules with bistable characteristics as reversibly tunable molecular switches in electrode/molecule/electrode configurations driven by external stimulations such as light  or current-pulse . We have modeled three kinds of molecular switch-junctions formed with silicon contacts and azobenzene derivatives which have bistable characteristics, i.e. both of cis- and trans-conformations. Using the non-equilibrium Green function (NEGF) approach  implemented with the density-functional-based tight-binding (DFTB) theory , we have analyzed a series of properties of the switch-junctions such as the electronic transmission, the on/off current and their ratio, potential energy surfaces as a function of reaction coordinate from cis- and trans-conformation. Furthermore, in order to investigate the stability of molecular switches in ambient conditions, we have performed molecular dynamics simulations (MD) at room temperature and calculated the time-dependent transmission fluctuations along the MD pathways . The numerical results have shown that transmission spectra in cis-conformations are more conductive than trans-conformations inside the bias window. I-V characteristics also lead to the same trends. Additionally, the calculations of time-dependent transmission fluctuations along with the MD pathways have shown that the transmission fluctuations in cis- and trans-conformations do not overlap with each other and can be distinguished at room temperature. Therefore, the azobenezene derivative-based molecular switches can be expected to work as robust organic switching components.
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Prof. Dr. Gianaurelio Cuniberti
Institute for Materials Science
visitors and courier address:
01062 Dresden, Germany