Sticky Molecular Surfaces: Epoxysilane Self-Assembled Monolayers

Abstract

Dense, homogeneous, and complete self-assembled monolayers with epoxy surface groups were fabricated from epoxysilanes to serve as a template for chemical anchoring of ultrathin polymer layers. We formed epoxysilane layers on silicon oxide surfaces of silicon wafers, and a combination of scanning probe microscopy, ellipsometry, XPS, and contact angle measurements was used to study their morphology and surface properties. A low concentration of epoxysilane (less than 0.5 vol %) led to significant aggregate formation caused by a prevailing hydrolization/polymerization of epoxysilane molecules in bulk solution. Epoxysilane SAMs prepared from 1% solution were truly monomolecular films with a virtually normal molecular orientation of densely packed molecules, which were firmly attached to the substrate. Self-assembly deposition of epoxysilanes at optimal conditions resulted in the formation of homogeneous SAMs 0.85 ± 0.2 nm thick with the surface roughness 0.22 ± 0.05 nm.