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Conductance Probing on Alkanethiols

Jessica Koehnea, Hou Tee Ngb, Geetha Dholakia*, c, Wendy Fanc, Jie Hanc, and M. Meyyappana

aNASA Ames Center for Nanotechnology NASA Ames Research Center,
Moffett Field, CA 94035 USA

bSETI Institute
cELORET, NASA Ames Research Center

This is an abstract for a presentation given at the
10th Foresight Conference on Molecular Nanotechnology


Monolayered self-assembly of novel organic molecules onto noble metals has been actively studied in recent years due to their applicability in molecular electronic devices. Various technological aspects of device fabrication and integration, in particular connecting a single molecule between contact leads poses challenges that have not yet been fully resolved. To some extent, self assembly solves the problem as the molecules are chemically anchored to the Au templates which then act as the active electrodes. Prior to fabricating three terminal devices like the field-effect transistors, one needs to acquire an understanding of the electron transport mechanism involved. In this abstract, we report on the electrical conductance measurements of a series of alkanethiolate molecules with potentially useful functionalities.

A relatively simple approach for the two terminal conductance measurements of the organic molecules has been performed with reasonably good reproducibility. Metallic probes with precise displacement control and with different radius-of-curvatures have been employed to probe the molecules with the possibility of investigating the electron transport phenomena through a single or a very few number of molecules and not a large ensemble. To demonstrate the feasibility of the techniques, a series of IV measurements, as shown in Figure 1, have been obtained by probing the tip onto the molecule. The IV curve obtained on just barely touching the sample is shown by the blue profile, which shows a bandgap of ~ 2.5eV (comparable to that obtained from scanning tunneling microscopy studies). Progressive changes in the IV profiles could be reproducibly observed while retracting and approaching the molecules. Further detailed studies will be done to determine whether the changes in the IV measurements are due to stresses imparted on the molecule or due to proximity of the tip to the Au contact.

Abstract in Microsoft Word® format 21,318 bytes

*Corresponding Address:
Geetha Dholakia
ELORET, NASA Ames Research Center
Mail Stop 229-1, Moffett Field, CA 94035 USA
Phone: 650-604-2171 Fax: 650-604-5244


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