Structure and morphology of self-assembled 3-mercaptopropyltrimethoxysilane layers on silicon oxide

Minghui Hu, Suguru Noda, Tatsuya Okubo, Yukio Yamaguchi, Hiroshi Komiyama

Research output: Contribution to journalArticle

154 Citations (Scopus)

Abstract

Self-assembled 3-mercaptopropyltrimethoxysilane (MPTMS, (CH3O)3SiCH2CH2CH2 SH) layers on hydroxyl-terminated silicon oxide (SiO2) were prepared at MPTMS concentrations ranging from 5 × 10-3 to 4 × 10-2M. The surface structure and morphology of MPTMS layers were characterized by X-ray photoelectron spectroscopy (XPS), contact angle measurements, scanning electron microscopy (SEM), and atomic force microscopy (AFM). We found that the MPTMS layers on SiO2 consisted of dispersed domains 20-200nm in diameter, instead of continuous, flat monolayers. With increasing MPTMS concentration, the domain shape changed from flat to steep. Flat domains were composed of well-ordered monolayers with thiol headgroups uniformly distributed on the uppermost surface, whereas steep domains were composed of disordered polymers with randomly distributed thiol headgroups on the uppermost surface. These results indicate that MPTMS molecules show good self-assembly at an MPTMS concentration of 5 × 10-3M, but not above this concentration. The effect of MPTMS concentration on the structure and morphology of MPTMS layers might be due to the competition between self-polymerization and surface dehydration reactions, which depends on the trace quantity of water in the solvent and on the SiO2 surface. Our research further indicates that MPTMS and water concentrations are the controlling parameters for preparing well-ordered, self-assembled MPTMS monolayers on SiO2.

Original languageEnglish
Pages (from-to)307-316
Number of pages10
JournalApplied Surface Science
Volume181
Issue number3-4
DOIs
Publication statusPublished - 2001 Sep 21
Externally publishedYes

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Keywords

  • Atomic force microscopy
  • Self-assembled monolayers
  • Silicon oxide
  • Surface modification
  • X-ray photoelectron spectroscopy

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Condensed Matter Physics

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