Role of elastic energy in the formation of ferroelectric barium strontium titanate films on sapphire

The initial stages of the growth of ferroelectric barium strontium titanate (BaSrTiO 3 ) films on single-crystal sapphire substrates have been investigated experimentally. It has been shown that the vapor-solid phase transition at the initial stage of the deposition of the BaSrTiO 3 film on sapphire occurs in two stages. At the first stage, an elastically strained wetting layer that inheres the structure of the substrate is formed on the surface. At the same time, a strong electric charge is formed on the surface of the wetting layer. At the second stage of the phase transition, the wetting layer loses stability and transforms into BaSrTiO 3 nuclei, which further merge to form a solid film.