AVS 51st International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuM

Paper SS2-TuM9
Designing Self-assembled Monolayers (SAM) of Thiols: A Study on Lattice Mismatch

Tuesday, November 16, 2004, 11:00 am, Room 210C

Session: Self Assembled Monolayers
Presenter: M. Buck, St Andrews University, UK
Authors: P. Cyganik, St Andrews University, UK
M. Buck, St Andrews University, UK
C. Woell, Ruhr-Universitaet Bochum, Germany
Correspondent: Click to Email
Applications of self-assembled monolayers (SAM) of thiols in, e.g., molecular electronics or electrochemistry are crucially dependent on the extent to which their properties can be controlled. Besides the control of the molecular electronic properties, controlling the structure, i.e., defects and crystallinity, is an issue of equal importance. As for any adsorbate system tailoring of SAMs has to address mismatch between molecular and substrate lattices. Surprisingly, this aspect which is of fundamental importance toward a controlled design of thiol SAMs has received very little attention. The talk presents STM studies on biphenyl based thiols which are characterized by an alkane spacer between the sulphur head group and the aromatic moiety. Within a homologue series of these biphenyl thiols with the spacer varying from 0 to 6 methylene units, intermolecular interactions, molecular orientation, and, thus, packing of the molecules are substantially changing. Contrast variations in scanning tunneling microscopy images reveal lattice mismatch. The way mismatch is accomodated depends strongly on the alkane spacer and, therefore, the achievable structural perfection is varying across the homologue series. The results suggest that a flexible spacer acts as a buffer layer which can accomodate mismatch between the lattice of aromatic moieties and the substrate lattice.