A vapor phase deposition of self-assembled monolayers: Vinyl-terminated films of volatile silanes on silicon oxide substrates

Vinyl-terminated self-assembled monolayers (SAMs) offer significant flexibility for further chemical modification and can serve as a versatile starting point for a tailoring of surface properties. A vapor phase deposition of such films would offer advantages in cases where the preparation from solution is not an option or not desired, for example in connection with silicon microstructures such as micro-electromechanical systems. We show that SAMs of 9-decenyltrichlorosilane (CH2=CH-(CH2)(8)-SiCl3), 10-undecenyltrichlorosilane (CH2=CH-(CH2)(9)-SiCl3), 14-pentadecenyltrichlorosilane (CH2=CH-(CH2)(8)-SiCl3), decyltrichlorosilane (CH3-(CH2)(9)-SiCl3), and octadecanetrichlorosilane (CH3-(CH2)(17)-SiCl3) can be prepared both from solution and from the vapor phase. The resulting layers were compared by static contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy to determine their surface wettability, the film thickness, the smoothness and homogeneity of the respective films, and their chemical composition and each method gave films of comparable quality. Deposition of functionalized SAMs from the vapor phase is rare. Here we report the parameters for the preparation of well-ordered vinyl-terminated SAMs from the vapor phase. (C) 2012 Elsevier B. V. All rights reserved.