Spatial tuning of the metal work function by means of alkanethiol and fluorinated alkanethiol gradients
Artikel i vetenskaplig tidskrift, 2009

Surface-chemical gradients composed of self-assembled monolayers (SAM) of deeanethiol (DT) and a partially fluorinated decanethiol (PFDT) on gold, exhibiting gradual changes in surface concentration of one or both components, have been prepared by a simple, controlled-immersion process. Infrared spectroscopic studies on a single-component PFDT gradient indicate a change in average molecular orientation with increasing surface coverage, whereas on a two-component gradient, the orientation remains invariant over the entire length of the gradient. X-ray photoelectron spectroscopic measurements on a single-component PFDT gradient show a systematic decrease in the fluorine (F Is) binding energy with increasing surface coverage, whereas a single-component DT gradient shows an increase in the carbon (C Is) binding energy. In two-component (DT-PFDT) gradients, the molar ratios of the two components at any particular location on the sample surface determine the magnitude of the binding-energy shifts at that location. Such shifts, which are on the order of 1 eV, are shown to be a consequence of work-function changes in the underlying gold upon SAM formation. These results are discussed in light of the surface-potential measurements on a DT-PFDT gradient by Kelvin Probe Force Microscopy and XP spectra acquired on "floating" and grounded samples.


Nagaiyanallur V. Venkataraman

Eidgenössische Technische Hochschule Zürich (ETH)

Stefan Zürcher

Eidgenössische Technische Hochschule Zürich (ETH)

Antonella Rossi

Eidgenössische Technische Hochschule Zürich (ETH)

Universita degli Studi di Cagliari

Seunghwan Lee

Eidgenössische Technische Hochschule Zürich (ETH)

Nicola Naujoks

Chalmers, Teknisk fysik, Kemisk fysik

Nicholas D. Spencer

Eidgenössische Technische Hochschule Zürich (ETH)

Journal of Physical Chemistry C

1932-7447 (ISSN) 1932-7455 (eISSN)

Vol. 113 14 5620-5628





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