AVS 50th International Symposium
    Contacts to Organic Materials Topical Conference Monday Sessions
       Session OM-MoM

Paper OM-MoM9
Study of Transport Through Organic Molecules on Semiconductor Surfaces Using STM-SPV

Monday, November 3, 2003, 11:00 am, Room 318/319

Session: Contacts to Molecules and Molecular Films (I)
Presenter: I. Nevo, Weizmann Institute of Science, Israel
Authors: I. Nevo, Weizmann Institute of Science, Israel
S.R. Cohen, Weizmann Institute of Science, Israel
D. Cahen, Weizmann Institute of Science, Israel
G. Haase, Weizmann Institute of Science, Israel
Correspondent: Click to Email
Mapping the potential of semiconductor surfaces using STM provides the ability to investigate electron transport properties through single molecules. The potential mapping is preformed by monitoring the tip-surface bias required to maintain a constant tunneling current under illumination termed - surface photovoltage (SPV). There is currently great interest in electron conduction through organic molecules attached to inorganic surfaces. However, many experiments probe an ensemble of nano-scale systems, thus, the effect of interface inhomogeneity is averaged out. Namely, it is not clear if and which of the molecular states participate in the electronic current passing through a system of a single molecule confined between two electrodes. Moreover, of the effect of an organic molecule on the local potential is unknown. In this work we investigate the transport properties of poly-aromatic molecules adsorbed on GaAs(110) and GaP(110) surfaces in ultra high vacuum and room temperature conditions. The bias dependence of the SPV images that are acquired simultaneously with the topography images indicates different tunneling mechanisms: direct tunneling, and resonant tunneling involving the molecular states. In addition, the potential surface varies with bias due to the changing overlap of molecular states with the tunneling energy interval.