Optimization of the buffer dielectric layer for the creation of low-defect epitaxial films of the topological insulator Pb$_{1-x}$Sn$_x$Te with $x\ge$ 0.4

We have optimized the growth conditions of the buffer layer for further deposition of Pb$_{1-x}$Sn$_x$Te ($x\ge$ 0.4), which has the properties of a crystalline topological insulator. To this end, a three-component heterostructure consisting of CaF$_2$, BaF$_2$, and Pb$_{0.7}$Sn$_{0.3}$Te : In layers was formed and optimized on the Si(111) surface. The surface morphology of this structure was studied depending on the temperature growth regimes and the optimal combination of growth parameters was selected from the point of view of smoothness and crystalline quality.