Effect of Annealing Temperature on the Thermoelectric Properties of the Bi0.5Sb1.5Te3 Thin Films Prepared by Radio-Frequency Sputtering

The effect of annealing temperature on the crystallinity, thermoelectric properties, and surface morphology of the Bi0.5Sb1.5Te3 thin films prepared on SiO2/Si substrate by radio-frequency (RF) magnetron sputtering was investigated using X-ray diffraction (XRD), the four-point probe method, and scanning electron microscopy (SEM). XRD results show that the crystallite structure of the Bi (x) Sb2-x Te-3 thin films belong to Bi0.5Sb1.5Te3. When the Bi (x) Sb2-x Te-3 thin films were annealed between 423 K and 523 K (150 A degrees C and 250 A degrees C) for 10 minutes, the crystallinity of the thin films continuously increases with the temperature increase. In addition, the (015) reflection plane as the preferred orientation and the oxidation compound of Bi3.73Sb1.5O3 first appeared when the Bi0.5Sb1.5Te3 thin films were annealed at 523 K (250 A degrees C) for 10 minutes. An activation energy of 51.66 kJ/mol for crystallite growth of Bi0.5Sb1.5Te3 thin films annealed between 423 K and 523 K (150 A degrees C and 250 A degrees C) for 10 minutes was obtained. The resistivity was 2.69 x 10(2) and 5.93 x 10 mu Omega A center dot m, respectively, for the as-deposited Bi0.5Sb1.5Te3 thin films and annealed at 523 K (250 A degrees C) for 10 minutes. The maximum values of the Seebeck coefficient and power factor were 256.5 mu V/K and 1.12 x 10(3) mu W/m center dot K-2, respectively, for the Bi0.5Sb1.5Te3 thin films annealing treatment at 523 K (250 A degrees C) for 10 minutes.