Evolution of the interface and metal film morphology in the vapor deposition of Ti on hexadecanethiolate hydrocarbon monolayers on Au

Timothy B. Tighe, Thomas A. Daniel, Zihua Zhu, Sundarajan Uppili, Nicholas Winograd, David L. Allara

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

The combination of in situ X-ray photoelectron spectroscopy, infrared reflection spectroscopy, atomic force microscopy, and time-of-flight secondary ion mass spectrometry are used to probe the nature of the evolving interface chemistry and metal morphology arising from Ti vapor deposition onto the surface of a CH 3(CH 2) 15S/Au{111} self-assembled monolayer (SAM) at ambient temperature. The results show that for a deposition rate of ∼0.15 Ti atom·nm -2·s -1 a highly nonuniform Ti overlayer is produced via a process in which a large fraction of impinging Ti atoms do not stick to the bare SAM surface. The adsorbed atoms form isolated Ti clusters and react with CH 3 groups to form carbide products at the cluster-SAM interfaces. Further growth of Ti clusters appears to be concentrated at these scattered reaction centers. The SAM molecules in the local vicinity are subsequently degraded to inorganic products, progressing deeper into the monolayer as the deposition proceeds to give an inorganic/organic nanocomposite. A continuous overlayer does not form until metal coverage approaches ∼50 Ti atoms per SAM molecule. These data indicate that for applications such as molecular device contacts the use of Ti may be highly problematic, suffering from both a highly nonuniform contact area and the presence of extensive inorganic products such as nonstoichiometric carbides and hydrides.

Original languageEnglish (US)
Pages (from-to)21006-21014
Number of pages9
JournalJournal of Physical Chemistry B
Volume109
Issue number44
DOIs
StatePublished - Nov 10 2005

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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