The study, published in the April 2007 issue of Nano Letters, showed that changing the head group of the organic molecules located far from the surface and changing the docking group provided two nearly independent ways to modify the metal work function.
While studying two metal substrates gold and silver the researchers found that even though the chemical interface between the metal and thiol-based self-assembled monolayer were different, the organic-covered metals had virtually identical work functions.
Postdoctoral research fellow Pavel Paramonov, who is now an assistant research professor at the University of Akron, expanded the original work to model the interface between a self-assembled monolayer and indium tin oxide, the conducting material commonly used as the transparent electrode in liquid crystal displays and organic light-emitting diodes.
"Researchers frequently cover the hydrophilic indium tin oxide surface with a self-assembled monolayer containing a hydrophobic subgroup pointing away from the surface, providing much better adherence and compatibility with the active organic layer that comes on top," said Brdas.
The cover layer also prevents the indium from diffusing into the active organic layer and degrading the device, but adding this layer also provides a way to fine-tune the work function.
With funding from the Solvay Group, Paramonov modeled the indium tin oxide surface, which was a complex task because indium tin oxide is not stoichiometric every vendor's indium tin oxide is somewhat different. Then he modeled the binding of a self-assembled monolayer of phosphonic acid to the indium tin oxide surface. Paramonov's first goal was to determine how the oxygen and phosphorus atoms of the self-assembled monolayer bind to the indium tin oxide surface.
In collaboration with Seth M
|Contact: Abby Vogel|
Georgia Institute of Technology Research News