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

Paper SS+OM-ThA6
Pronounced Odd-Even Changes in the Molecular Arrangement and Packing Density of Biphenyl-Based Thiol SAMs: A Combined STM and LEED Study

Thursday, November 6, 2003, 3:40 pm, Room 327

Session: Self-Assembled Monolayers
Presenter: P. Cyganik, University of StAndrews, UK
Authors: P. Cyganik, University of StAndrews, UK
M. Buck, University of StAndrews, UK
W. Azzam, Ruhr Universitaet Bochum, Germany
G. Witte, Ruhr Universitaet Bochum, Germany
Ch. Woell, Ruhr Universitaet Bochum, Germany
Correspondent: Click to Email
Self-assembled monolayers (SAMs) of thiols are promising candidates for nanolithographic applications. Towards a rational design and control down to the length scale reaching molecular dimensions we study SAMs a particular type of thiols which is characterized by a biphenyl unit and an alkane spacer of varying length (CH@sub 3@ (C@sub 6@H@sub 4@)@sub 2@(CH@sub 2@)@sub n@SH, BPn, n = 2, 3, 4, 5). SAMs adsorbed on Au(111) substrates were studied using scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). Our results demonstrate that preparation at elevated temperature results in highly ordered layers with large domains. Whereas the (2@sr@3x@sr@3) structure of the BP3 and BP5 SAMs is similar to that reported previously for other aromatic thiols, SAMs made from BP2 and BP4 exhibit a very different structure. A (5@sr@3x3)rect unit cell containing 8 molecules is found which corresponds to a packing density reduced by 25 % compared to BP3 and BP5. The odd-even effect observed in the molecularly resolved STM images of BPn, therefore, confirms the pronounced influence of the spacer chain on the structure of these biphenyl based SAMs.