The implementation of force detection in experiments on electron transport through
single molecules.
Prof. Dr. Jascha Repp, Institute for Experimental and Applied Physics, Regensburg [Homepage]
By means of scanning tunneling microscopy (STM) it is possible to investigate electron
transport through adsorbates and adsorbate structures in a large variety of aspects,
while having exact knowledge and control of the atomistic structure including
the coupling to the leads. Therefore, STM has been very successfully applied in the
field of molecular electronics. However, STM investigations are limited to conducting
substrates and the experimental data is determined by both the geometry and the electronic
structure of the sample in a complex and often ambiguous manner.
To overcome these two limitations it is projected to experimentally implement force
detection as an additional measure in molecular electronics, that is, in electron transport
measurements through a single molecule. To this end a scanning tunneling microscope
equipped with a force detector at the tip shall be developed and built. It is
planned to measure the forces that act on the tip upon contact formation to a single
molecule, to provide a more complete set of experimental data that can be used to
model and understand the contact formation. Second, we would like to implement the
force detection to unambiguously discriminate between electronic and geometric effects
in the current signal in imaging as well as in any electron-transport measurement.
Third, the possibilities in quantifying charge redistribution in molecules and molecular
structures by electrostatic force detection will be explored. Finally, the force detection
shall also enable to find conducting molecular structures for systems containing completely
insulating sample areas.
Altogether this project shall establish the detection of forces in experiments on electron
transport through molecules and thereby provide a better control of the geometry
in molecular electronics with atomic-scale precision.