Point defects in the mixed chalcogenides Bi2 Te3-xXx(X = S, Se)

From the dependences of electrical conductivity [sgrave]1 and the Hall constant RH( B ‖ C ) of Bi2 Te3-xSx crystals upon the value of x it is found that a transition from hole-like to electron-like conductivity takes place at x × 0.12. The decrease in the hole concentration with increasing x is explained by the idea that an increasing content of incorporated S atoms in the anion sublattice gives rise to an increase in the anion vacancy concentration (VA) and simultaneously the antisite defect concentration increases slightly as well. This model is not in contradiction with van Vechten's theory of the formation of vacancies in a crystal lattice. The results obtained for the system of Bi2Te3-xSx are compared with those for the system Bi2Te3-xSex.