Correlation of microwave dielectric properties and crystallinity for pulsed laser deposited Bi₂(Zn_1/3 Nb_2/3)₂O₇ thin films

Correlation of microwave dielectric properties of Bi₂(Zn_1/3Nb_2/3)₂ O₇, BiZN thin films, which were pulsed laser deposited on Si(100) substrates, with crystallinity of BiZN phase was examined using Fourier Transform Infrared (FTIR) spectroscopy. Rigid-ion model analysis from FTIR spectra of the films reveals that the magnitude of effective charge for oxygen increases with improved crystallinity for BiZN films. In contrast, lattice vibrational modes of the films, which occur at ω ₀₁=341 cm^-1, ω₀₂=522 cm^-1, and ω ₀₃=612 cm^-1, insignificantly change with films' crystallinity. It implies that better crystallinity will induce higher polarization in BO₆ oxygen octahedral, which improves microwave properties of pyrochlore materials. The dielectric constant measured at 200 cm^-1 increases with substrate temperature used for depositing BiZN films, inferring that dielectric properties in low frequency regime of far infrared region are predominantly contributed by ionic polarization, and are strongly related to effective charges of oxygen species.