jeudi 27 avril 2017 à 14H00 (Thé à 15h)
CINaM - Salle Raymond Kern
Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic
Exploring functionalities of single molecules on surface by scanning probe microscopy
The field of molecular electronics aims at using a single molecule as building block for electronic devices. In this talk we will discuss different functionalities of molecules on surfaces investigated by means of scanning tunneling microscopy. First, we will present experimental evidence of controlling multiple charge states on a single 3,6,3‘,6‘-tetraferrocene-9,9’bis-fluorenylidene, deposited on thin insulating NaCl film, by means of nc-AFM. We succeed to control the multiple charge states including their reversible transfer within a single molecule between different redox states. The induced charged states have prominent fingerprints in both the frequency shift and dissipation channels. Moreover, we demonstrate that the charge states can be modified by presence of neighboring charged molecules.
In second, we will discuss large converse piezoelectric effect observed in a single heptahelicene-derived molecule deposited on the Ag(111). The force-distance spectroscopy acquired over a wide range of bias voltages reveals a linear shift of the tip-sample distance, at which the contact between the molecule and tip apex is established. We demonstrate that this effect is caused by the bias-induced deformation of the spring-like scaffold of the helical polyaromatic molecules. The experimental evidences are corroborated with a theoretical model simulating response of a dynamically oscillating AFM probe to temporal changes of force due to the charging effects of molecules on surface.
Invitation : Olivier Siri - Entrée libre