Control of moisture at buried polymer/alumina interfaces through substrate surface modification

Bryan D. Vogt, Vivek M. Prabhu, Christopher L. Soles, Sushil K. Satija, Eric K. Lin, Wen Li Wu

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Moisture absorption in poly(4-tert-butoxycarbonyloxystyrene) (PBOCSt) films supported on Al 2O 3 sputter coated silicon wafers is measured using neutron and X-ray reflectivity. Accumulation of water at the interface during moisture exposure results in an apparent film-thickness- dependent swelling for ultrathin PBOCSt films. The swelling of a film on Al 2O 3 is less than the swelling of a film of the same thickness on SiO x for films thinner than 20 nm. This is due to comparatively less moisture accumulation at the Al 2O 3/PBOCSt interface. A simple, zero adjustable parameter model consisting of a fixed water-rich layer at the interface and bulk swelling through the remainder of the film describes the thickness-dependent swelling quantitatively. The influence of four different Al 2O 3 surface treatments on the moisture distribution within PBOCSt films was examined: bare Al 2O 3, tert-butylphosphonic acid, phenylphosphonic acid, and n-octyltrichlorosilane. Both the phenyl and the octyl surface treatments reduce the accumulation of water at the polymer/substrate interface. The tert-butyl treatment does not reduce the interfacial water concentration, presumably due to insufficient surface coverage.

Original languageEnglish (US)
Pages (from-to)2460-2464
Number of pages5
Issue number6
StatePublished - Mar 15 2005

All Science Journal Classification (ASJC) codes

  • General Materials Science
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry


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