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 rg as a function of the deposition temperature. The rg line shape indicates that in a wide range of temperatures (∼180–400 °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 EA 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 EA ≃ 27.6 kJ/mol.