Smooth, Aggregate-Free Self-Assembled Monolayer Deposition of Silane Coupling Agents on Silicon Dioxide

摘要

Silane coupling agents (SCAs) are notorious fornaggregating during deposition on oxide substrates, leading tonnonuniform surface morphologies. To ameliorate thisnproblem, we describe a vapor-phase deposition technique fornsilane coupling agents employing a spin-coated perfluoropolyethern(PFPE) diffusion barrier that facilitates the formationnof smooth, aggregate-free self-assembled monolayers (SAMs).nSamples fabricated using PFPE barrier layers yielded SAMsnexhibiting similar water contact angles, reduced water contactnangle hysteresis, and a 2-fold reduction in rms roughnessnrelative to those without a barrier. X-ray photoelectronnspectroscopy confirms that the barrier layer can be completelynremoved after deposition, leaving behind a smooth monolayer.nA basic analysis of the agglomerate separation ability of thenbarrier layers is discussed to understand the critical parametersninvolved. Generalized guidelines for selecting barrier materialsnare presented.