Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 110: Molecular Films: Morphology, Electronics, Photovoltaics

O 110.5: Vortrag

Freitag, 24. März 2017, 11:45–12:00, GER 38

Determination of large converse piezoelectric effect on a single moleculeOleksander Stetsovych1, •Martin Svec1, Pingo Mutombo1, Ondrej Krejci1, Irena Stara2, Ivo Stary2, and Pavel Jelinek11Institute of Physics, CAS, Praha, Czech republic — 2Institute of Chemistry and Biochemistry, CAS, Praha, Czech republic

The converse piezoelectric effect is a phenomenon, in which a mechanical strain is generated in a material due to an applied electrical field. Demonstration of the piezoelectric effect on nanoscale remains a challenge. In this work, we investigate the piezoelectric effect in single 2,17-Bis(acetylsulfanyl) heptahelicene (BA7H) molecules on Ag(111), using the non-contact atomic force microscopy (AFM). The BA7H on the substrate forms various islands, which can be effectively disassembled to individual molecules by the AFM tip, to exclude collective influence on the piezoelectric measurements. The acetylsulfanyl group at the terminal of the molecule exposed to the tip can be reversibly rotated between two metastable configurations via tip interactions. We characterized the bias-induced deformations of the BA7H and found that the piezoelectric constant is independent of the acetylsulfanyl group conformation, thereby demonstrating the piezoelectric effect is intrinsic to the helicene core. The total energy DFT calculations reveal strong charge transfer between BA7H molecule and the metallic substrate, which gives rise to a vertical electric dipole, which causes together with a soft vibrational mode of the molecule the strong piezoelectric effect.

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