Initial stages of growth of barium zirconate titanate and barium stannate titanate films on single-crystal sapphire and silicon carbide

The initial stages of growth of barium zirconate titanate and barium stannate titanate ferroelectric films on single-crystal sapphire and silicon carbide are studied for the first time. The choice of substrates is dictated by the possibility of using such structures in ultra-high frequency devices. The growth of discontinuous BaZr$_{x}$Ti$_{1-x}$O$_{3}$ films is found to be mediated by the gas phase mass transport mechanism in the studied temperature range. For deposition of BaSn$_{x}$Ti$_{1-x}$O$_{3}$ films, the mechanism of mass transport switches at $\sim$800$^{\circ}$C from surface diffusion to gas phase diffusion; also, the films deposited on sapphire and silicon carbide have considerably different elemental composition. The formation of an intermediate SiO$_2$ layer is noted on silicon carbide during the growth of oxide films on this substrate, its thickness depending on the deposition temperature.