Fig. 4 shows the carrier concentration, electron mobility, electrical and power factor for the Bi-Te films.
As the annealing temperature increases, the carrier concentration and mobility vary in the opposition direction, the carrier concentration from 53.4 x 1019 to 5.5 x 1019 lem and the mobility significantly rising from 9 to 64 cm IV s. The increase of the mobility appears to be linked to the microstructure changes, since the grain size in crease leads to the facilitation of current flow and thus anenhancement in the mobility by reducing the number of grain boundaries 18,9]. The resistivity peaks at an intermediate temperature, around 423 K, as shown in Fig. 4(b).
Fig. 4 Electrical transport properties and power factor for as deposited and annealed Bi-Te
films. (a)carrier concentration and electro mobility, (b) resistivity, and (c) power factor