Peculiarities of Bi4_4Ti3_3O12_{12} films grown by DC magnetron sputtering

The peculiarities of the synthesis and crystallization of complex oxides (B$_4$Ti$_3$O$_{12}$ as an example) from the decay products in magnetron sputtering are discussed. The processes of complex oxide sputtering by ion bombardment, transfer of the products through the plasma to the substrate, the surface processes on the substrate and oxidation-reduction processes are considered. The dynamics of the layer formation is investigated by measuring the spectral line intensities ($\lambda_{\rm Bi} = 472.25$ nm and $\lambda_{\rm Ti} = 498.1$ nm) of the sputtered atoms at the target surface. The film deposition mechanism is shown to change with distance between substrate and target. A critical distance of $h_{\rm crit} = 7$ nm is found. At $h < h_{\rm crit}$ atoms are deposited, while at $h > h_{\rm crit}$ molecules condense. The degree of crystallization depends on oxygen pressure. Thermal activation strongly affects the deposition rate. In the case of molecular deposition at temperatures of $\geq 900~^\circ$C the high-temperature phase of $\gamma$-Bi$_2$O$_3$ forms along with Bi$_2$O$_3$ and TiO$_2$. The dielectric loss tangent of Bi$_4$Ti$_3$O$_{12}$ films depends on the bias potential of the substrate