ABSTRACT
Neutron reflection was used to study the interaction of water vapor with films of bis(triethoxysilyl)ethane (BTSE). BTSE provides a hydrophobic surface and has been shown to impart corrosion resistance to certain metals under favorable conditions. The silane coatings were applied to the oxide surfaces of polished silicon wafers. Neutron reflectivity was obtained from the ~150–600 Å silane layers after exposure for 48 h to air saturated with either D2O or H2O. Both D2O and H2O provide scattering contrast with the dry BTSE film. A large increase in reflectivity was observed upon conditioning with D2O, but no change in reflectivity was observed upon conditioning with H2O. Upon evacuation of the sample conditioned with D2O, a strong decrease in reflectivity was observed. These results are not consistent with simple absorption of water into the film. Rather, the results indicate that a substantial fraction of unhydrolyzed ethoxysilyl groups remain within the as-prepared films, and are hydrolyzed upon conditioning with H2O or D2O to form silanol groups. The silanol groups apparently condense upon evacuation to liberate H2O or D2O. Little physically absorbed water is present within the conditioned films at room temperature in saturated air.
