Electrical contacts to organic molecular films by metal evaporation: effect of contacting details

H Haick, O Niitsoo, J Ghabboun… - The Journal of Physical …, 2007 - ACS Publications
The Journal of Physical Chemistry C, 2007ACS Publications
We show that electron beam evaporation of metal onto a monolayer of organic molecules
can yield reproducible electrical contacts, if evaporation is indirect and the sample is on a
cooled substrate. The metal contact forms without damaging even the molecules' outermost
groups. In contrast, direct evaporation seriously damages the molecules. By comparing
molecular effects on metal/molecular layer/GaAs junctions, prepared by indirect evaporation
and by other soft contacting methods, we confirm experimentally that Au is not an optimal …
We show that electron beam evaporation of metal onto a monolayer of organic molecules can yield reproducible electrical contacts, if evaporation is indirect and the sample is on a cooled substrate. The metal contact forms without damaging even the molecules' outermost groups. In contrast, direct evaporation seriously damages the molecules. By comparing molecular effects on metal/molecular layer/GaAs junctions, prepared by indirect evaporation and by other soft contacting methods, we confirm experimentally that Au is not an optimal choice as an evaporated contact metal. We ascribe this to the ease by which Au can diffuse between molecules, something that can, apart from direct contact−substrate connections, lead to undesired and uncontrollable interfacial interactions. Such phenomena are largely absent with Pd as evaporated contact.
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