Ferroelectric properties of heterostructure Sr$_{0.5}$Ba$_{0.5}$Nb$_2$O$_6$/Ba$_{0.2}$Sr$_{0.8}$TiO$_3$/Si(001)

The properties of c-oriented thin films of Sr$_{0.5}$Ba$_{0.5}$Nb$_2$O$_6$ grown on a Si(001) ($p$-type) substrate with a pre-deposited Ba$_{0.2}$Sr$_{0.8}$TiO$_3$ layer were studied using scanning probe microscopy and dielectric spectroscopy. It is established that the Sr$_{0.5}$Ba$_{0.5}$Nb$_2$O$_6$ films are characterized by low surface roughness (less than 6 nm) and average crystallite size of $\sim$93 nm. It is shown that there is spontaneous polarization in the film directed from its surface to the substrate, which causes the manifestation of the field effect for the case of the Si substrate with $p$-type conductivity without the external field effect. Differences in the magnitudes of the surface potential signal for regions polarized by an external electric field of different polarities (+10 and -10 V), as well as in their relaxation to the initial state, are revealed. The reasons for the established patterns are discussed.