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TU Dresden » Faculty of Mechanical Science and Engineering » Institute for Materials Science » Chair of Materials Science and Nanotechnology

» presentations   » 2008.11.04-06

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 [1] or current-pulse [2]. 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 [3] implemented with the density-functional-based tight-binding (DFTB) theory [4], 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 [5]. 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.
[1] M. del Valle, R. Gutierez, C. Tejedor, and G. Cuniberti, Nature Nanotech. 2, 176 (2007).
[2] H. Riel et al., Small 2, 977 (2006).
[3] A. Pecchia and A. Di Carlo, Rep. Prog. Phys. 67, 1497 (2004).
[4] T. Frauenheim et al., J. Phys. Cond.-Matt. 14, 3015 (2002).
[5] A. Pecchia, et. al., Phys. Rev. B 68, 235321 (2003).

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