Abstract: Examples are disclosed that relate to acid-stabilized precursor solutions for metal oxide film deposition, and to films deposited using the disclosed acid-stabilized precursor solutions. One disclosed example provides an aqueous precursor solution for forming a metal oxide film by liquid-phase deposition, the precursor solution comprising metal ions, a photolyzable and/or pyrolyzable ligand, and an acid. Another example provides a method of forming a metal oxide film, the method comprising coating a substrate with an aqueous precursor solution comprising metal ions, a photolyzable and/or pyrolyzable ligand, and an acid to form a film, and curing the film. Examples also are disclosed that relate to methods of fabricating optical waveguides using solution-based deposition of metal oxide films, followed by patterning. Examples are also disclosed that relate to optical waveguides fabricated according to the disclosed methods.