Ion beam mixing to produce Bi/Sb alloys for thin film thermoelectric devices

Ion beam mixing using 80 keV Ar+ and 120 keV Kr+ has been used to produce thin films of BiSb with various compositions of Sb ranging from 5% to 49%. In addition, n- and p-type doping of the films was attempted by the addition of Se and Sn during the mixing process. Rutherford backscattering analysis indicated that uniform composition films were formed after doses of 1.5–3 × 1016 Ar+cm−2and 7 × 1015 Kr+cm−2. TEM measurements show that grain growth occurs during the mixing. Thermo-electric measurements indicate that the Seebeck coefficient, S, has a maximum value of 66 μVK. for an Sb concentration of 13%. This alloy also exhibits a 30% increase in the figure of merit over that of a pure Bi film. Attempts to dope the BiSb films using Sn and Se resulted in no change in S but an increase of 35% in the Seebeck voltage, Vs.