AVS 51st International Symposium
    Surface Science Monday Sessions
       Session SS2-MoA

Paper SS2-MoA7
Competition as Design Concept in Self-Assembled Monolayers

Monday, November 15, 2004, 4:00 pm, Room 210C

Session: Assembled Monolayers
Presenter: P. Cyganik, St Andrews University, UK
Authors: P. Cyganik, St Andrews University, UK
M. Buck, St Andrews University, UK
Correspondent: Click to Email
Self-assembled monolayers (SAMs) of aromatic thiols adsorbed on Au(111) substrates were studied using scanning tunneling microscopy (STM). Our experiments show that a molecular design, which is not based on the usual concept of energy minimization but employs competing forces, opens an unexpected additional dimension in the control of structure and properties of thiol SAMs. Based on thiols which are characterized by a combination of a biphenyl unit and an alkane spacer (CH@sub 3@(C@sub 6@H@sub 4@)@sub 2@(CH@sub 2@)@sub n@SH, BPn, n = 2, 3, 4, 5, 6), the length of the spacer is chosen such that different factors which determine the energetics of a SAM structure (e.g. sulfur bonding geometry vs. intermolecular interactions) enter in a competing rather than a cooperative way. The SAMs prepared according to this concept show thermally induced irreversible transitions into new structures. This transition is paralleled by striking improvement in the structural perfection of the SAM and changes in the stability against exchange by other thiols.