title: Control of moisture at buried polymer/alumina interfaces through substrate surface modification.
abstract: Moisture absorption in poly(4-tert-butoxycarbonyloxystyrene) (PBOCSt) films supported on Al(2)O(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(2)O(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(2)O(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(2)O(3) surface treatments on the moisture distribution within PBOCSt films was examined: bare Al(2)O(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.
authors.affiliation: Polymers Division and Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA. bryan.vogt@nist.gov
authors.forename: Bryan D
authors.initials: BD
authors.lastname: Vogt
authors.forename: Vivek M
authors.initials: VM
authors.lastname: Prabhu
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Soles
authors.forename: Sushil K
authors.initials: SK
authors.lastname: Satija
authors.forename: Eric K
authors.initials: EK
authors.lastname: Lin
authors.forename: Wen-li
authors.initials: WL
authors.lastname: Wu