Spatial tuning of metal work function by means of alkanethiol and fluorinated alkanethiol gradients

Nagaiyanallur V. Venkataraman, Stefan Zürcher, Antonella Rossi, Seunghwan Lee, Nicola Naujoks, Nicolas D. Spencer

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Surface-chemical gradients composed of self-assembled monolayers (SAM) of decanethiol (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 1s) binding energy with increasing surface coverage, whereas a single-component DT gradient shows an increase in the carbon (C 1s) 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.
Original languageEnglish
JournalJournal of Physical Chemistry Part C: Nanomaterials and Interfaces
Volume113
Issue number14
Pages (from-to)5620-5628
ISSN1932-7447
DOIs
Publication statusPublished - 2009
Externally publishedYes

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