Electrical Contacts to Organic Molecular Films by Metal Evaporation: Effect of Contacting Details
Author(s):
Hossam Haick, Olivia Niitsoo, Jamal Ghabboun, David Cahen
Journal:
The Journal of Physical Chemistry C
Year:
2007
Volume:
111
Pages
2318-2329
DOI:
10.1021/jp065357p
Abstract:
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.