Low temperature magnetothermoelectric effect and magnetoresistance in Te vapor annealed Bi₂Te₃

The electrical properties of single crystals of p-type Bi ₂Te₃ are shown to be tuned by annealing as-grown crystals in elemental Te vapor at temperatures in the range of 400-420 °C. While as-grown nominally stoichiometric Bi₂Te₃ has p-type conductivity below room temperature, Te vapor annealed Bi₂Te ₃ shows a cross over from p- to n-type behavior. The temperature dependent resistivity of the Te annealed crystals shows a characteristic broad peak near 100 K. Applied magnetic fields give rise to a large low temperature magnetothermoelectric effect in the Te annealed samples and enhance the low temperature peak in the resistivity. Further, Te annealed Bi₂Te ₃ shows a large positive magnetoresistance, ∼200% at 2 K, and ∼15% at room temperature. The annealing procedure described can be employed to optimize the properties of Bi₂Te₃ for study as a topological insulator.