Annealing effect on thermoelectric properties of Bi implanted Si thin film

We have investigated the electrical transport properties of a series of bismuth implanted silicon film which have different dose amounts and post-annealing conditions. The Hall measurement data show that the electrical activation yield decreases after thermal annealing for the samples with dose amount N_d=3×10¹⁵ and 3×10¹⁴ cm^-2, while the yield remains almost unchanged for those with N_d=3×10¹³ and 3×10¹² cm^-2. This tendency strongly suggests that the metastable bismuth atoms form precipitates in the silicon crystal during the postannealing process when the dose amount is larger than its solubility limit. The Seebeck coefficient S of the high-dose samples also changes with post-annealing temperature. Comparing the measured transport coefficients with those of phosphorous or arsenic doped bulk silicon crystals, it was found that the excess Bi atoms reduce the mobility and this leads to lower electrical conductivity. The Seebeck coefficient is slightly lower than arsenic doped silicon