Metals are reacted in a first solvent, such as 2-methoxyethanol, to form an initial precursor comprising metal-oxide compounds dissolved in the first solvent. A second solvent, such as xylene, that does not react with the metal is added to the solution and the solution heated to distill away the first solvent and form a final precursor. The final precursor is spin-coated on an integrated circuit substrate then dried and annealed to form a thin film of a metal oxide. For metal oxides including bismuth, the bismuth precursor is added to a cold initial precursor and the final precursor is not heated after the bismuth precursor is added. The second solvent wets the substrate better than the first solvent and has a better viscosity for spin-coating, thus resulting in a denser thin film with fewer imperfections.