Role of ion irradiation induced defects in thermoelectric transport properties of Bi_2Te_3 thin films

摘要

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 x 10(15)ions/cm(2) exhibited highest power factor value of similar to 6.3 mu W/mK(2) at room temperature.