Different point defects originated from dissimilar deposition conditions in n-type Cu-doped Bi2Te3 films; crystal structure and thermoelectric property depending on Te-vacancy concentration

We found that two types of Cu-doped Bi2Te3 thin films fabricated by dissimilar sputter process had different microstructures and non-stoichiometries (Bi:Te ratios). We investigated the different levels of Te-vacancy (V-Te(2+)) concentration in the films affected the point defects and the thermoelectric property of the films. The Cu additives were substituted for the Bi-sites (form Cu-Bi(2-) defects) in case of a low Te-vacancy concentration (V-Te(2+)) in the Bi2Te3 thin film. In the high V-Te(2+)-defect concentration case, the Cu-Bi(2-)-formation reaction was thought to be inhibited and evidences for the Cu-additive intercalating into a van der Waals layer (a Cu-vdW defect) were detected. We examined the lattice parameter, the thermoelectric properties, and the carrier transport properties of the two types of thin films with the different Te-vacancy concentrations as evidences for the different point defect formation characteristics between them. The Te-vacancy (V-Te(2+)) dependency of the point defects formation (Cu-Bi(2-) or Cu-vdW) in this system can suggest the clue to control an atomic scale Cu-site in n-type Cu doped Bi2Te3 thin films. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).