Effects of Gas-Phase Thermal Decompositions of Chemical Vapor Deposition Source Molecules on the Deposition of (Ba, Sr)TiO3 Films: A Study by In Situ Fourier Transform Infared Spectroscopy

We studied the thermal decompositions of Ti(t-BuO)2(DPM)2, Sr(DPM)2 and Ba(DPM)2 under actual chemical vapor deposition (CVD) conditions by in situ Fourier transform infrared spectroscopy (FT-IR). From the temperature dependence of the IR absorbance, we investigated the thermal stability of the chemical bonds in the source molecules. The obtained FT-IR data were correlated with the characteristics of the deposited BST films. Although Sr(DPM)2 and Ba(DPM)2 molecules decompose completely in the gas phase before Sr and Ba atoms are incorporated in the film, the deposition of Ti atoms does not require the complete decomposition of Ti(t-BuO)2(DPM)2 molecules in the gas phase. In this study, we discuss the effects of these thermal decompositions on the deposition mechanism of (Ba,Sr)TiO3 films.