Synthesis and microstructural characterization of layered Cu–Sb–Te–based thin films

Chalcogenides are promising materials for various applications due to their tunable properties through materials design. In this work, Cu–Sb–Te thin films are synthesized via Cu diffusion into epitaxial Sb 2 Te 3 thin films using room–temperature DC magnetron sputtering. X–Ray diffraction shows that the diffusion of Cu into the Sb 2 Te 3 is strongly dependent on deposition pressure. A simulation of the sputtering process using a Monte Carlo approach reveals that the Ar working gas pressure impacts the kinetic energy of the sputtered atoms. At lower deposition pressures and therefore higher kinetic energy more Cu diffuses. This results in the formation of disordered layered Cu–Sb–Te structures embedded with Sb 2 Te 3 matrix. Interestingly, a new Cu 7 (Sb 0.4 Te 0.6 ) 4 phase is obtained by further sputter deposition of Pt and Ti layers on top of the Cu layers at room temperature. The phase represents a layered structure consisting of 3Te layers per building unit. Structure analysis using advanced transmission electron microscopy indicates the formation of Te and Sb antisite defects and a crystal structure model for this phase is proposed based on the microscopy analysis. An additional thermal in situ XRD heating of the Cu 7 (Sb 0.4 Te 0.6 ) 4 results in out–diffusion of Sb and the formation of Cu 7 Te 4 structures consisting of 2Te and 3Te layers as well as Sb 2 O 3 , showing strong diffusion of oxygen. The Cu 7 (Sb 0.4 Te 0.6 ) 4 and Cu 7 Te 4 layers retain epitaxial properties of the former Sb 2 Te 3 layers. This approach allows for the synthesis of chalcogenides consisting of disordered Cu–Sb–Te and Sb 2 Te 3 structures as well as the fabrication of epitaxial disordered Cu 7 (Sb 0.4 Te 0.6 ) 4 thin films.