On the incorporation of germanium atoms into the Bi2Te3 crystal lattice

The incorporation of Ge atoms into Bi2Te3 crystals is studied by X-ray powder diffraction method and Weissenberg photographs of single crystals of Bi2Te3 + x at% Ge with x = 0 to 15. At low Ge concentration the Ge atoms enter preferentially Bi-sublattice forming thus substitutional defects GeBi. For x > 3.5 the Ge atoms create new structural planes inside the van der Waals gaps of the Bi2Te3 structure resulting in the formation of a modulated structure. For single crystals of Bi2Te3 + 5 at% Ge and Bi2Te3 + 15 at% Ge the lattice parameters of the new superlattice are determined.