We explore the usability of molecules with bistable characteristics as reversibly tunable molecular switches driven by external stimulation such as light [1] or current-pulse [2]. We have modeled three molecular switch-junctions formed with silicon contacts and azobenzene derivatives which have bistable cis-and trans-conformations. Using the nonequilibrium Green?s function approach implemented with the density-functional-based tight-binding theory [3], we analyzed electron transmission, on/off ratios, potential energy surfaces along reaction coordinate from cis-to trans-conformation, and the stability of the molecular switches in ambient conditions along MD pathways. The numerical results have shown that transmission spectra in cis-conformations are more conductive than trans-ones inside of the bias window in three models. I-V characteristics also lead to the same trends. Additionally, the transmission along MD pathways have shown that the cis-conformations are always more conductive than trans-ones at room temperature. Therefore, the azobenzene derivative-based molecular switches can be expected to work as robust switching components.

[1] M. del Valle et al., Nature Nanotech. 2, 176 (2007).
[2] H. Riel et al., Small, 2, 973 (2006).
[3] A. Pecchia et al., Rep. Prog. Phys. 67, 1497 (2004).