Microstructure and thermoelectric properties of rapidly quenched Bi_xSb_100-x thin film alloys

The electric resistivity, ρ, and the Seebeck coefficient, S, of amorphous and polycrystalline (anealed) Bi_x Sb_100-x films have been measured in the temperature range between 5 K and 350 K. The amorphous films were prepared in situ by the flash evaporation technique at low temperature (T ≈ 10 K). Values of S(T) of the amorphous samples show pronounced dependences on the bismuth content as far as x < 20 at% Bi and in the region 75 < x/at% Bi < 90. The behaviour of S(T) in the region x < 20 at% Bi is dominated by the disorder-driven metal-insulator transition which appears at approximately 10-15 at% Bi. On the other hand, between 75 and 90 at% Bi very small crystalline clusters which are embedded in the amorphous matrix even after vapour quenching are responsible for the large variation of S(T) when the composition of the thin films is changed.