Growth kinetics of TiO2 films deposited by aerosol-assisted chemical-vapor deposition from two different precursors (Ti-n-butoxide and Ti diisopropoxide)

Abstract

When titanium dioxide films are deposited by delivering a liquid aerosol of titanium-n-butoxide or titanium diisopropoxide, the crystalline and morphological features indicate that the deposition takes place through an aerosol-assisted chemical-vapor deposition (AA-CVD) process. However, the crystalline state depends on the precursor. The evidence of AA-CVD is strongly supported by the quantitative study of the growth rate rg as a function of deposition temperature. The fitting of the experimental rg curves to the equation ∼T3∕2exp(−EA∕RT) indicates that film formation is limited by the gas diffusion + surface reaction of the precursors. The characteristic activation energy EA of such surface reaction depends on the Ti precursor; EA≅112.0kJ∕mol for Ti-n-butoxide and EA≅21.4kJ∕mol for Ti-diisopropoxide.

TiO2 Nanoparticles prepared by MOCVD: effect of temperature, flowrate, and precursor

“…These results seem to be consistent with the results obtained by Conde‐Gallardo et al . and Falaras and Xagas who both made direct comparison between TiO 2 thin films deposited by aerosol‐assisted CVD and TiO 2 thin films prepared via sol–gel technique from both TBOT and TTIP precursors.…”

“…To the best of our knowledge, no report has been published on the effects of MOCVD parameters (temperature and carrier gas flowrate) on the TiO 2 nanoparticles produced using titanium (IV) butoxide (TBOT) as the precursor, although TBOT has been proved to produce purer TiO 2 crystalline structure, with smaller and more uniform grain size than TTIP . In a previous study, we reported the effect of postdeposition heat treatment on the size, crystallinity, and photocatalytic activity of the TiO 2 nanoparticles produced via MOCVD method using TBOT precursor .…”

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

“…Nevertheless, by comparing these values with those obtained in Ref. 18 (E A ‫ס‬ 21.4 kJ/ mol), where nitrogen was used as the carrier gas, it is observed that the environment has a relatively more important influence on the activation energy. This dependence on the environment can also be observed by comparing the vertical scale of Fig.…”

“…18 Therefore, this clearly shows that we are dealing with an AA-MOCVD process and that those two phenomena must be considered as the limiting mechanisms for the film formation. In fact, by leaving B and E A as free parameters in a least-squares nonlinear regression fitting procedure, similar values are obtained for the activation energy E A ‫ס‬ 26.4 and 28.8 kJ/mol (average ∼27.6 kJ/mol) for solutions 1 and 2, respectively.…”

${\rm Nd}_{1-{\rm x}}{\rm Fe}_{\rm x}{\rm OF}$ Thin Films Deposited by Chemical Vapor Deposition and Their Arsenic Diffusion

“…The films studied in this work were grown by the "aerosol assisted chemical vapor deposition" technique (AA-CVD) [12], [13]. An ultrasonic generator set at 0.8 MHz, which produces droplets of 1-5 in average size, was employed to produce the aerosol to be injected in a cold wall chamber.…”