The effect of gas-phase reaction on the deposition of Pb(ZrTi)O-3 films by metal organic chemical vapor deposition (MOCVD) was in situ investigated by Fourier Transform Infrared (FTIR) spectroscopy. Pb(C11H19O2)(2), Zr(O.t-C4H9)(4), and Ti(O.t-C3H7)(4) were used as source gases, which was widely investigated for MOCVD-Pb(Zr,Ti)O-3 deposition. We investigated various source-gas combinations and detected a gas-phase reaction in the mixtures containing Zr source gas. Moreover, the deposition rates of the Zr and Ti oxides in the films were found to be determined by the actual source gas concentration after gas-phase reaction and could be controlled by the absorbance spectrum intensities of the Zr and Ti source gases. In contrast, the deposition rate of the Ph oxide was mainly determined by the surface reaction on the substrate for making PZT single phase. (c) 2005 Elsevier B.V. All rights reserved.