Local structure and anti-structural defects of tin in amorphous and crystalline Ge$_{2}$Sb$_{2}$Te$_{5}$ films

The absorption Mössbauer spectroscopy on $^{119}$Sn impurity centers shows that germanium atoms in the structure of amorphous and polycrystalline Ge$_{2}$Sb$_{2}$Te$_{5}$ films have different local symmetries (tetrahedral in the amorphous phase and octahedral in the crystalline). By emission Mössbauer spectroscopy on $^{119 m}$Sn impurity centers formed after the radioactive decay of $^{119}$Sb or $^{119m}$ Te parent atoms, tin antisite defects at antimony and tellurium sites of crystalline Ge$_{2}$Sb$_{2}$Te$_{5}$ films are identified.