AVS 50th International Symposium
    Surface Science Thursday Sessions
       Session SS+OM-ThA

Paper SS+OM-ThA5
Balance of Structure-building Forces in Monomolecular Films: Terphenyl-substituted Alkanethiolates on Noble Metal Substrates

Thursday, November 6, 2003, 3:20 pm, Room 327

Session: Self-Assembled Monolayers
Presenter: A. Shaporenko, Universität Heidelberg, Germany
Authors: A. Shaporenko, Universität Heidelberg, Germany
M. Brunnbauer, Universität Hamburg, Germany
A. Terfort, Universität Hamburg, Germany
L.S.O. Johansson, Karlstad University, Sweden
M. Zharnikov, Universität Heidelberg, Germany
Correspondent: Click to Email
The design of versatile monomolecular films relies on detailed knowledge of basic rules governing the packing density and exact arrangement of the molecular constituents in these systems. The most important issue in this connection is the understanding of the interplay between the structure- building headgroup-substrate and intermolecular interactions. To address this issue we have studied self-assembled monolayers (SAM) formed from terphenyl-substituted alkanethiols C@sub 6@H@sub 5@(C@sub 6@H@sub 4@)@sub 2@(CH@sub 2@)@sub n@SH (TPn, n = 1-6) on Au and Ag substrates. In these systems, strongly interacting terphenyl backbones force a dense molecular packing, which does not fit to the geometry of the metal-S-C bond at certain length of the aliphatic part. We used several complementary experimental techniques such as x-ray photoelectron spectroscopy (XPS), high-resolution XPS, near edge X-ray absorption fine structure spectroscopy, infrared absorption spectroscopy, ellipsometry, and water contact angle measurements to characterize the TPn SAMs. Odd-even changes in the packing density, the tilt angle of the terphenyl moieties, etc have been observed and considered in detail. There changes could be clear correlated with the geometry of the metal-S-C bond, which assumed to be different on Au and Ag. The results imply a predominant role of the headgroup-substrate interaction in the balance of structure-building forces in the aliphatic SAMs and give a practical tool for the fabrication of monomolecular films with desired properties.