Heteroepitaxial Barium Strontium Niobate Films: Structure, Lattice Dynamics, and Dielectric Properties in the Range 0.1–2.5 THz

–- We have studied the structure, lattice dynamics, and dielectric properties (terahertz spectroscopy) of heteroepitaxial Sr 0.5 Ba 0.5 Nb 2 O 6 films grown on MgO (001) substrates by rf cathode sputtering in an oxygen atmosphere. The results demonstrate that the films are heteroepitaxial and homogeneous and have high structural perfection. According to analysis of Raman spectra of the films measured at various temperatures in the range 299–433 K, the behavior of individual vibrational modes shows anomalies at T ≃ 390 ± 10 K, related to the phase transition. The unit cell of barium strontium niobate films 2.4–2.5 μm in thickness is shown to undergo strain both along and across the plane of the interface. Presumably, this is responsible for the increase in the width of the ferroelectric phase transition according to Raman spectroscopy data and also for the observed variations in the dielectric properties of the films in the terahertz frequency range.