Growth kinetics of self-assembled monolayers of thiophene and terthiophene on Au(111): An infrared spectroscopic study |
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Authors: | T Matsuura Y Shimoyama |
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Institution: | (1) Department of Applied Physics, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan, JP;(2) Department of Physics, Hokkaido University of Education, Hakodate 040-8567, Japan, JP |
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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.
Received 23 May 2001 and Received in final form 11 February 2002 |
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Keywords: | 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 |
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