Fermi Level Alignment in Self-Assembled Molecular Layers: The Effect of Coupling Chemistry

Published

August 1, 2006

Author(s)

Christopher D. Zangmeister, Steven W. Robey, Roger D. van Zee

Abstract

Photoelectron spectroscopy was used to explore changes in Fermi level alignment, within the p-p* gap, arising from changes in the coupling chemistry of conjugated phenylene ethynlene oligomers to the Au surface. Self-assembled monolayers were formed employing either thiol (4,4 -ethynylphenyl-1-benzenethiol or OPE-T) or isocyanide (4,4 -ethynylphenyl-1-benzeneisocyanide or OPE-NC) coupling. The electronic density of states in the valence region of the two systems are nearly identical with the exception of a shift to higher binding energy by about 0.5 eV for OPE-NC. Corresponding shifts in C(1s) spectra and in the threshold near Ef. The lack of change in the optical absorption suggests a rigid shift of the Fermi level within the p-p* gap is the major effect of modifying the coupling chemistry. Qualitative consideration of bonding in each case is used to suggest the influence of chemisorption-induced charge transfer as a potential explanation. Connections to other theoretical and experimental work on varying coupling chemistries in molecular layers are discussed.

Citation

Journal of Physical Chemistry B

Volume

110

Issue

34

Pub Type

Journals

Keywords

band line-up, monolayer, photoemission

Citation

Zangmeister, C. , Robey, S. and van, R. (2006), Fermi Level Alignment in Self-Assembled Molecular Layers: The Effect of Coupling Chemistry, Journal of Physical Chemistry B (Accessed April 16, 2024)