Role of ion irradiation induced defects in thermoelectric transport properties of Bi2Te3 thin films

Highlights: • Defects were infused in Bi2Te3 thin films using He+ and Ar+ ion irradiation. • He+ ions increases hole concentration. • Ar+ ions induces grain melting and suppresses hole concentration. • Maximum power factor achieved in films for He+ ion irradiation fluence of 1 × 1015ions/cm2. Present study investigates the contribution of defects in the thermoelectric transport properties of Bi₂Te₃ thin films using 120 keV He⁺ and Ar⁺ ion irradiation. Charge carrier type is converted from n-type to p-type with He⁺ ion irradiation. Upon Ar⁺ ion irradiation, thin film exhibited p-type conductivity at lower ion fluence and n-type conductivity at higher ion fluences. In case of He⁺ ion irradiation, bismuth vacancies were suggested to increase hole density and responsible for p-type conductivity whereas in the case of Ar⁺ ion irradiation, Ar⁺ ion induce grain melting that suppresses defect density and consequently increases electron concentration. Bi₂Te₃ films irradiated with the He⁺ ion fluence of 1 × 10¹⁵ions/cm² exhibited highest power factor value of ~6.3 μW/mK² at room temperature.