Characterization of the Microstructure of Sr_0.75Ba_0.25Nb₂O₆ Thin Films by Brillouin Light Scattering

Strontium-barium niobate (Sr_xBa_(1-x)Nb₂O₆) films can be considered as a promising material for microwave applications due to high dielectric nonlinearity and relatively low losses. Since strontium-barium niobate has a disordered structure that determines its unique electrical properties, the identification of structural features of the Sr_xBa_(1-x)Nb₂O₆ films is the key to their successful use. The Sr_xBa_(1-x)Nb₂O₆ films were synthesized on a sapphire substrate by magnetron sputtering. The structure of the films was studied by both traditional methods of electron microscopy, X-ray diffraction, and the rarely used for thin films investigation Brillouin light scattering method, which was the focus of our study. We show that Brillouin light scattering is an excellent nondestructive method for studying the structural features of thin ferroelectric strontium-barium niobate films. An analysis of the features of the Brillouin light scattering spectra in thin-film structures and their comparison with the spectra of bulk crystals allowed us to determine with high accuracy the thickness of the films under study and their structural features determined by the resonant scattering of acoustic waves.