Electrical molecular switch addressed by chemical stimuli
H. Audi, Y. Viero, N. Alwhaibi, Z. Chen, M. Iazykov, A. Heynderickx, F. Xiao, D. Guérin, C. Krzeminski, I. M. Grace, C. J. Lambert, O. Siri, D. Vuillaume, S. Lenfant, H. Klein
Abstract
We demonstrate that the conductance switching of benzo-bis(imidazole) molecules upon protonation depends on the lateral functional groups. The protonated H-substituted molecule shows a higher conductance than the neutral one (Gpro > Gneu), while the opposite (Gneu > Gpro) is observed for a molecule laterally functionalized by amino-phenyl groups. These results are demonstrated at various scale lengths: self-assembled monolayers, tiny nanodot-molecule junctions and single molecules. From ab initio theoretical calculations, we conclude that for the H-substituted molecule, the result Gpro > Gneu is correctly explained by a reduction of the LUMO-HOMO gap, while for the amino-phenyl functionnalized molecule, the result Gneu > Gpro is consistent with a shift of the HOMO, which reduces the density of states at the Fermi energy.