Laser-assisted spray pyrolysis process for the growth of TiO₂ and Fe₂O₃ nanoparticle coatings

We present a laser-assisted spray pyrolysis method to fabricate nanoparticle coatings of metal oxides. In this process, 1.5-μm size droplets of a titanium- or iron-containing organometallic precursor were injected into a vacuum chamber with SF₆ carrier gas. The strong absorption of a 3W CO₂ laser beam focused onto the injector tip in the presence of SF₆ increased the temperature of the gas and the droplets to about 300 °C. Films deposited on heated substrates with and without the CO₂ laser heating were studied by atomic force microscopy. The laser heating of the droplets caused the solvent to evaporate before depositing on the substrate, leading to grain sizes that are about a factor of 3 smaller than those deposited without laser heating. By controlling the concentration of the precursor in the solvent, the average particle sizes have been tuned from 80 to 50 nm.