Tomorrow: PhD defense, Nazanin Davani, Monday (March 7), 11 am, Packard 202

Nazanin Davani ndavani at stanford.edu
Sun Mar 6 17:21:13 PST 2011


*Electrical and Optical Characterization of Molecular Junctions*

Nazanin Davani

Stanford University PhD Dissertation Defense-Department of Chemical
Engineering

Research Advisor: Professor Nicholas A. Melosh

* *

*March 7th** (Monday), 2011 @ 11 am*

(Refreshments served at 10:45 am)



Location: Packard 202

http://ee.stanford.edu/directions.php?bld=packard

Electronic transport through molecules has been intensively studied in
recent years, due to scientific interest in fundamental questions about
charge transport and the technological promise of nanoscale circuitry. A
variety of experimental platforms have been developed to electronically
probe molecular junctions. However, it remains challenging to fabricate
reliable electronic contacts to molecules, and the vast majority of
molecular electronic architectures are not amenable to standard
characterization techniques, such as optical spectroscopy. Interesting
phenomena like switching and rectification are observed in molecular
junctions. However, due to limited quantitative information about the
junction, the mechanism remains unknown and many fundamental questions about
electronic transport remain unanswered.

The first part of the presentation will introduce the fabrication of
Metal-Insulator-Metal (MIM) cross bar junctions using soft deposition
technique. In this method, we softly deposit the premade metal contacts that
are being supported with a polymer backing layer onto the organic layer.
Using this method, we can efficiently fabricate large area, non-shorting
devices, which are required for optical characterization of the molecular
junctions.

Having established a means of fabricating reliable molecular devices, we
have investigated the switching mechanism in molecular junctions based on
n-type semiconductor Perylene tetracarboxylic diimide (TE-PTCDI) molecules.
Using Surface Plasmon Resonance Spectroscopy (SPRS) we have been able to
perform simultaneous optical-electrical measurements to study the molecular
behavior *quantitatively*. Using in-situ optical spectroscopy on active
molecular junctions, we find that only a small fraction of the molecules are
actually switching in the junction. Finally, I present the results of our
studies on the molecular rectification in C60-diamondoid hybrid molecules in
large area junctions, as well as in smaller ensemble of molecules. The
statistical studies along with a theoretical model show the origin of
rectification in such molecular devices.
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