Molecules on insulators

 

Aim : Realize supramolecular self-assemblies on insulating surfaces

 

During the last five years, the use of insulating substrates in nanosciences and nanotechnologies has continued to receive incresased interest because they allow a total decoupling between the molecular orbitals and the surface. This property is necessary for opto-electronic applications. At the international level, there are only about ten examples of supramolecular assemblies on this type of substrate. In 2011, our group joined a consortium combining our skills in surface physics/chemistry to those of groups specialized in atomic force microscopy in order to study charge transfers within supramolecular networks on insulating surfaces.

 

This consortium profits from the financial support of the ANR (non-thematic action, NANOKAN project, the biggest project financed by ANR "Action Thématique" in 2011, 1 M€/4 years). To achieve the proposed scientific aims, we've developed four generations of molecules which allow to create these assemblies on KCl, NaCl and RbCl surfaces. Networks are observed by atomic force microscopy under ultra-high vacuum, what allows to obtain a sub-molecular resolution. The supramolecular self-assemblies geometry is fixed by the respective influence of molecules-molecules (van der Waals) and molecules-surface (electrostatic) interactions. The surface covered by the self-assemblies is about square micron, which is 10 times greater than best results published at the present time.

This work is closely coordinated with C. Loppacher and L. Nony (IM2NP) and A. Shluger (UCL - London).

 

A) Atomistic representation  of a ML of CDB molecules on KCl(001). B) vAFM image of the ML imaged using a 10 Debye point dipole for the tip and a tip–sample distance of 0.8 nm. C) NCAFM topography image of CDB molecules on KCl(001) at room temperature (frame edge = 12 nm). Experimental and vAFM parameters: γ = –0.04 nN√nm, A 0 = 10 nm.