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Direct measurement of electrical conductance through a self-assembled molecular layer
1Institute for Storage Ring Facilities, and Interdisciplinary Nanoscience Center, University of Aarhus, Aarhus C, Denmark.
Nature Nanotechnology
|June 6, 2009
Summary
Self-assembled cobalt phthalocyanine layers conduct electricity only when molecules stand up in thicker films. This finding is crucial for designing future nanoelectronic devices based on molecular self-assembly.
Area of Science:
- Materials Science
- Nanotechnology
- Surface Science
Background:
- Self-assembly of organic molecules on surfaces is key for nanoelectronic devices.
- Understanding the electrical conductance of molecular links is crucial but limited.
- Extended electronic states are necessary for good molecular conductance on metal surfaces.
Purpose of the Study:
- To measure the conductivity of self-assembled cobalt phthalocyanine layers on a silver-terminated silicon surface.
- To investigate the relationship between molecular orientation, film thickness, and electrical transport properties.
Main Methods:
- Utilized a nanoscale four-point probe technique.
- Measured conductivity as a function of cobalt phthalocyanine layer thickness.
- Investigated molecular orientation (lying flat vs. standing up) on the substrate.
Main Results:
- At low thicknesses, cobalt phthalocyanine molecules lie flat, reducing substrate conductivity.
- At higher thicknesses, molecules stand up, forming stacks that exhibit conductivity.
- Demonstrated a thickness-dependent transition in conductivity linked to molecular orientation.
Conclusions:
- Molecular orientation and film thickness critically influence the transport properties of self-assembled organic layers.
- Findings provide insights for rational design of molecular electronic devices.
- Connects electronic structure and orientation to transport properties in molecular systems.
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