Temperature dependent phase segregation and morphology evolution in Ca1−xBaxF2 solid solution grown on Si(001) with an epitaxial CaF2 sublayer

Abstract

The work presents the results of synthesizing epitaxial heterostructures based on the Pb_1−ySn_yTe/BaF₂/Ca_1−xBa_xF₂/CaF₂/Si(001) system. A comprehensive study of these heterostructures was performed, the surface morphology was characterized, the lattice parameters of each sublayer was determined, and the temperature dependence of phase segregation of the Ca_1−xBa_xF₂ solid solution into binary components was identified. Optimization of the growth conditions of CaF₂ on Si(001) reduced the surface area occupied by pit defects by 14%. It was shown that the use of a metamorphic Ca_1−xBa_xF₂ buffer layer improves lattice constant matching between CaF₂ and BaF₂ layers. It was established that the optimal growth temperature of the Ca_1−xBa_xF₂ solid solution, providing maximum surface planarity, is around 300 °C, with further temperature increase to 475 °C and above leading to solid solution segregation.