Gas-phase diffusion and surface reaction as limiting mechanisms in the aerosol-assisted chemical vapor deposition of TiO2 films from titanium diisopropoxide

Titanium dioxide thin films were deposited on crystalline silicon (100) substrates by delivering a liquid aerosol of titanium-diisopropoxide. The evidence of a metalorganic chemical vapor deposition process observed in the crystalline and morphological features of the films is strongly supported by the behavior of the growth rate r(g) as a function of the deposition temperature. The r(g) line shape indicates that in a wide range of temperatures (similar to 180-400 degrees C), the film formation is limited by both gas-phase diffusion of some molecular species toward the substrate surface and the thermal reaction of those species on that surface. The activation energy E-A that characterizes the surface reaction depends somewhat on the precursor concentration; a fitting procedure to an equation that takes into account both limiting mechanisms (gas-phase diffusion + surface reaction) yields E-A similar or equal to 27.6 kJ/mol.