Electrical and Thermoelectric properties of Bi2(Te1-xSex)3 thin films

Abstract

The alloys of Bi2[Te1-x Sex]3 (were prepared by melting technique with different values of the Se percentage (x=0,0.1,0.3,0.5,0.7,0.9 and 1)..Thin films of these alloys were prepared using thermal evaporation technique under vacuum of 10-5 Torr on glass substrates, at room temperature with deposition rate (12nm/min) with constant thickness (450±30 nm).The D.C conductivity measurements showed two stages of activation energy and hence two transport mechanisms for Bi2[Te1-x Sex]3 thin films, throughout the heating temperature range (323-433)K. The results of Hall Effect measurement show that all thin films have p-type conductivity. The carrier concentrations of charge carriers nH decrease with increasing of Se percentage, from 2.32*1019cm-3 at x=0 to 9.40*1017cm-3 at x=1, while the Hall mobility μH showed opposite manner which increases with increasing of Se percentage from 3.51*10-1 cm2/V.s when x=0 to 7.54cm2/V.s at x=1. The carrier mobility increases with increasing of Se percentage. Thermoelectric properties of Bi2[Te1-x Sex]3films were measured from (323 to 433) K. The values of Seebeck coefficient, the power factor and thermal conductivity Kel were decreased with increasing of Se percentage in all samples of Bi2(Te1-xSex)3 thin films. The figure of Merit (ZT) decreases by increasing (Se) percentage for all investigated Bi2(Te1-xSex)3 thin films, from 0.7048 at x= 0 to 0.1298 at x=1.