Titanosilicate ETS-10 thin film preparation on fused silica optical fibers

Abstract

Thin ETS-10 films have been prepared for the first time on fused silica optical fibers by dip coating followed by secondary growth. Nearly continuous films were obtained by a single dip coating of the optical fiber surface modified by partially hydrolyzed tetraethyl orthosilicate (TEOS). These films were composed of a monolayer of ETS-10 seeds (crystal distribution mode 0.84 ± 0.02 μm). Only modified fibers yielded intact films after exposure to flowing water for 24 h. Film thickness increased to 1.8 ± 0.3 μm when the number of dip coating steps increased from one to three. Hydrothermal treatment of single dip coated films resulted in seed crystal removal from the fibers. Secondary growth of crystals deposited by triple dip coating promoted intergrowth of seed crystals and resulted in continuous films attached to the fibers. Film thickness increased from 2.0 ± 0.3 to 4.4 ± 0.3 μm upon increasing the secondary growth step duration from 2 to 24 h. Secondary growth for 6 h or longer resulted in separation of the films from the fibers; this was likely due to partial dissolution of the fibers in the growth solutions. Analysis of the microstructure of films obtained in the secondary growth step indicates the films grew via epitaxial growth of the seed crystals.