Influence of molecular ordering on electrical and friction properties of ω-(trans -4-stilbene)alkylthiol self-assembled monolayers on Au (111)

Yabing Qi, Xiaosong Liu, B. L.M. Hendriksen, V. Navarro, Jeong Y. Park, Imma Ratera, J. M. Klopp, C. Edder, Franz J. Himpsel, Jean Frechet, Eugene E. Haller, Miquel Salmeron*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

The electrical and friction properties of ω-(trans-4-stilbene) alkylthiol self-assembled monolayers (SAMs) on Au(111) were investigated using atomic force microscopy (AFM) and near edge X-ray absorption fine structure spectroscopy (NEXAFS). The sample surface was uniformly covered with a molecular film consisting of very small grains. Well-ordered and flat monolayer islands were formed after the sample was heated in nitrogen at 120 °C for 1 h. While lattice resolved AFM images revealed a crystalline phase in the islands, the area between islands showed no order. The islands exhibit substantial reduction (50%) in friction, supporting the existence of good ordering. NEXAFS measurements revealed an average upright molecular orientation in the film, both before and after heating, with a narrower tilt-angle distribution for the heated fim. Conductance-AFM measurements revealed a 2 orders of magnitude higher conductivity on the ordered islands than on the disordered phase. We propose that the conductance enhancement is a result of a better π-π stacking between the trans-stilbene molecular units as a result of improved ordering in islands.

Original languageEnglish (US)
Pages (from-to)16522-16528
Number of pages7
JournalLangmuir
Volume26
Issue number21
DOIs
StatePublished - Nov 2 2010

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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