Tuning the conductance of a molecular wire by the interplay of donor and acceptor units
D. Skidin, T. Erdmann, S. Nikipar, F. Eisenhut, J. Krueger, F. Guenther, S. Gemming, A. Kiriy, B. Voit, D.A. Rydnyk, C. Joachim, F. Moresco, G. Cuniberti
Nanoscale 10, 17131 (2018)
We investigate the conductance of optimized donor-acceptor-donor molecular wires obtained by on-surface synthesis on the Au(111) surface. A careful balance between acceptors and donors is achieved using a diketopyrrolopyrrole acceptor and two thiophene donors per unit along the wire. Scanning tunneling microscopy imaging, spectroscopy, and conductance measurements done by pulling a single molecular wire at one end are presented. We show that the conductance of the obtained wires is among the highest reported so far in a tunneling transport regime, with an inverse decay length of 0.17 A(-1). Using complex band structure calculations, different donor and acceptor groups are discussed, showing how a balanced combination of donor and acceptor units along the wire can further minimize the decay of the tunneling current with length.