Characterizing the molecular order of phosphonic acid self-assembled monolayers on indium tin oxide surfaces

Mark D. Losego, Joshua T. Guske, Alina Efremenko, Jon Paul Maria, Stefan Franzen

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Self-assembled monolayers (SAMs) of alkanephosphonic acids with chain lengths between 8 and 18 carbon units were formed on thin films of indium tin oxide (ITO) sputter-deposited on silicon substrates with 400 nm thermally grown SiO 2. The silicon substrates, while not intended for use in near-IR or visible optics applications, do provide smooth surfaces that permit systematic engineering of grain size and surface roughness as a function of the sputter pressure. Argon sputter pressures from 4 to 20 mTorr show systematic changes in surface morphology ranging from smooth, micrometer-sized grain structures to <50 nm grains with 3× higher surface roughness. Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy experiments are conducted for alkanephosphonic acids deposited on these wide range of ITO surfaces to evaluate the effects of these morphological features on monolayer ordering. Results indicate that long-chain SAMs are more highly ordered, and have a smaller tilt angle, than short-chain SAMs. Surprisingly, the 1-octadecyl phosphonic acids maintain their order as the lateral grain dimensions of the ITO surface shrink to ∼50 nm. It is only when the ITO surface roughness becomes greater than the SAM chain length (∼15 Å) that SAMs are observed to become relatively disordered.

Original languageEnglish (US)
Pages (from-to)11883-11888
Number of pages6
JournalLangmuir
Volume27
Issue number19
DOIs
StatePublished - Oct 4 2011

Fingerprint

Self assembled monolayers
Tin oxides
indium oxides
Indium
tin oxides
surface roughness
acids
Acids
Surface roughness
Silicon
Chain length
Phosphorous Acids
X ray absorption near edge structure spectroscopy
silicon
Argon
Crystal microstructure
micrometers
Substrates
roughness
grain size

All Science Journal Classification (ASJC) codes

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

Cite this

Losego, Mark D. ; Guske, Joshua T. ; Efremenko, Alina ; Maria, Jon Paul ; Franzen, Stefan. / Characterizing the molecular order of phosphonic acid self-assembled monolayers on indium tin oxide surfaces. In: Langmuir. 2011 ; Vol. 27, No. 19. pp. 11883-11888.
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Characterizing the molecular order of phosphonic acid self-assembled monolayers on indium tin oxide surfaces. / Losego, Mark D.; Guske, Joshua T.; Efremenko, Alina; Maria, Jon Paul; Franzen, Stefan.

In: Langmuir, Vol. 27, No. 19, 04.10.2011, p. 11883-11888.

Research output: Contribution to journalArticle

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