Doping amount dependence of phase formation and microstructure evolution in heavily Cu-doped Bi2Te3 films for thermoelectric applications

Heavily Cu-doped Bi2Te3 films with different Cu contents (similar to 47.9 at%) were prepared by co- sputtering with Cu and Bi2Te3 targets at room temperature and post-annealing at similar to 500 degrees C. When the Cu content increased, the lattice parameters of the c-axis gradually increased with the increase of Cu intercalation into van der Waals gaps between the quintets of the Bi2Te3 layers. When a Cu content of above 43.7 at% was added, formation of a Cu2Te phase was detected along with the phase transition from Bi2Te3 to Te-deficient BixTey in the films annealed at 300 degrees C. The porous column structure of the pure Bi2Te3 film became gradually dense with the increase of Cu content. When the Cu content was increased, the thermoelectric power factors of heavily Cu-doped Bi2Te3 films were enhanced by the increase of carrier concentration.