Quantum Chemical Study on Chemical Vapor Deposition Source Molecules for the Deposition of (Ba,Sr)TiO 3 Films: Infrared Band Identifications by Density Functional Calculations

The vibrational spectra of the chemical vapor deposition (CVD) source molecules used for the deposition of (Ba,Sr)TiO 3 films were investigated by density functional theory (DFT) calculations. On the basis of the DFT calculations, we revised a part of the traditional assignments of the infrared spectral peaks. The spectral peaks of Ti( t -BuO) 2 (DPM) 2 at 627 cm -1 and 578 cm -1 were found to correspond to the Ti–O vibrations in the β-diketone chelate rings and in the alkoxy groups, respectively. These new assignments made it possible to elucidate the difference in the reactivity between the β-diketone chelate rings and the alkoxy groups of the Ti source molecules such as Ti( t -BuO) 2 (DPM) 2 . In addition to the Ti source molecules, we demonstrated that the DFT calculation was applicable for the analysis of the vibrational spectra of Ba and Sr source molecules, Ba(DPM) 2 and Sr(DPM) 2 .