Eur. Phys. J. E 7, 233-240 (2002)
DOI: 10.1140/epje/i200101073

Growth kinetics of self-assembled monolayers of thiophene and terthiophene on : An infrared spectroscopic study

T. Matsuura¹ and Y. Shimoyama<sup>2

1</sup>  Department of Applied Physics, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
²  Department of Physics, Hokkaido University of Education, Hakodate 040-8567, Japan

yuhei@cc.hokkyodai.ac.jp

(Received 23 May 2001 and Received in final form 11 February 2002)

Abstract
The growth kinetics of self-assembled monolayers (SAMs) of thiophene compounds on Au(111) surfaces was revealed by Fourier-transform infrared reflection absorption spectroscopy (FT-IR-RAS). Thiophene and terthiophene form well-ordered SAMs on Au(111) surfaces by immersing gold substrates into their ethanol solutions for ca. 15 h. Gibbs free energies for the adsorption processes of thiophene and terthiophene were found to be identical. However, the growth and molecular orientation of SAMs are different between two thiophene compounds. Terthiophene in SAMs orients parallel to the surface. The SAM growth of terthiophene obeys a time-dependent Langmuir scheme. On the other hand, the thiophene SAM undergoes a two-step growth process with unique molecular orientations. In the primary phase, thiophene assumes a parallel orientation on the Au(111) surface. In the second phase, thiophene is oriented close to the normal of the surface. The different growth process between thiophene and terthiophene is attributable to the topology of sulfur positions in the molecules.

PACS
68.55.-a - Thin film structure and morphology.
81.10.Aj - Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation.
78.30.-j - Infrared and Raman spectra.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002