AVS 53rd International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM1-ThA

Paper EM1-ThA3
Oxygen-Modified Interaction of Evaporated Titanium with Organic Monolayers

Thursday, November 16, 2006, 2:40 pm, Room 2001

Session: Contacts to Organic and Molecular Devices
Presenter: J.J. Blackstock, Hewlett Packard Labs
Authors: J.J. Blackstock, Hewlett Packard Labs
W.F. Stickle, Hewlett Packard Company
C.L. Donley, Hewlett Packard Labs
D. Ohlberg, Hewlett Packard Labs
D.R. Stewart, Hewlett Packard Labs
R.S. Williams, Hewlett Packard Labs
Correspondent: Click to Email
Due to ease of integration with conventional fabrication techniques, the evaporation of metal onto organic monolayers is a common method for making electrical contact to one side of a molecular electronic junction. In particular, titanium has frequently been employed as the deposited metal in molecular electronic devices, based on the assumption that the Ti atoms would interact with the top of the monolayer and form a covalent titanium-carbide bond. However, a range of recent studies have demonstrated that under some deposition conditions, titanium is more reactive than originally anticipated, and can cause significant damage to the organic monolayer. Herein we present data on the evaporation of titanium onto Langmuir-Blodgett (LB) monolayers of alkane chains. We utilize a new technique, based on the cleaving of molecular electronic device stacks at the organic interface in UHV, to investigate the interaction of the titanium with the alkane chains as a function of the underlying substrate. UHV XPS and in-situ IR data reveal that the previously observed damage to organic monolayers by evaporated titanium is strongly mitigated by the presence of available oxygen from the underlying substrate. Furthermore, angle-resolved XPS data on these systems elucidate a kinetic mechanism by which the damage to an organic monolayer proceeds beyond the top layer of the monolayer when available oxygen is not present in the substrate. In combination with previous studies, these data suggest the potential to engineer substrate-monolayer systems to produce desirable interactions between evaporated titanium contacts and organic monolayers.