Deposition of Vanadium(V) Oxide Thin Films on Nitrogen-Containing Self-Assembled Monolayers

Abstract

Vanadium oxide films have been deposited from aqueous solutions at low temperature on different self-assembled monolayer (SAM) modified silicon surfaces. Amine and ammonium salt SAMs were made via in situ transformations of bromide SAMs. The crystal structure and chemical composition of the vanadium oxide films were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The films on alkylammonium salt SAMs were 3−4 times thicker than on amine SAMs under identical deposition conditions. In all cases, V2O5·1.6H2O formed first (in the first 24 h), followed by V2O5·H2O. The film growth rate showed two separate growth periods corresponding to the formation of these two phases. Mixed-valence and mixed-phase vanadium oxide films could be achieved by controlling the deposition conditions, whose effect on the kinetics of film growth has also been studied. Films up to 80 μm thick on alkylammonium salt SAM and 16 μm thick on amine SAM were grown in 72 h.