Effect of substitution of Ti by Zr in BaTiO 3 thin films grown by MOCVD

Abstract

Thin films of the solid solution BaTiO 3–BaZrO 3 were studied. Such lead-free, environmental friendly materials are known, from dielectric measurements, to exhibit relaxor behaviour in bulk materials with increasing the Zr content. Ba[Ti (1− x) Zr x ]O 3 thin films with various x values were prepared by liquid injection MOCVD by varying the corresponding x′ value in solution (from 0.00 to 0.80). The films were studied by X-ray diffraction, Raman spectroscopy and microprobe analysis. A single perovskite phase with a linear evolution of the out-of-plane lattice parameter was identified by X-ray diffraction up to x′=0.25. For higher Zr contents a secondary ZrO 2 phase was detected. Raman spectroscopy was used to follow the subtle evolution of the crystal structure as a function of the chemical composition. The dielectric properties of single-phase layers were investigated in the range 20–600 K and 0.02–100 kHz. For some composition, the measured dielectric constant displayed a frequency-dependent behaviour.