Thermoelectric Properties of Bi2Te3 and Bi0.5Sb1.5Te3 Thin Films and Their Energy Generating Performance

Abstract

We report on the influence of post-annealing on the crystalline structures, chemical position, and thermoelectric (TE) properties-including Seebeck coefficient, electric resistivity, power factor, and thermal conductivity-of both n-type Bi2Te3 (n-BT) and p-type Bi0.5Sb2Te3 (p-BST) thin films with a thickness of 300 nm, which are prepared by radio-frequency (RF) sputtering. For this study, the samples are annealed at temperatures of 20, 100, 200, and 300 degrees C under Ar atmosphere. From the measured TE properties, both n-BT and p-BST thin films annealed at 200 degrees C exhibit the highest TE performance. The samples reveal resistivities of 2.2x10(-4) Omega cm and 7.7x10(-3) Omega cm, Seebeck coefficients of -45 mu V/K and 190 mu V/K, and power factors of 9.6x10(-4) W/K-2 m and 4.7x10(-4) W/K-2 m for 200 degrees C annealed n-BT and p-BST thin films, respectively. In addition, we obtain that the average thermal conductivities of the annealed n-BT and p-BST thin films to be similar to 0.2-0.6 W/(m . K) and similar to 0.3-0.5 W/(m . K) at room temperature using the 3-omega method, respectively, indicating a slight increase with increasing annealing temperatures. Furthermore, the TE performance of a thin-film-based TE energy generator consisting of n-BT and p-BST thin film legs on Si substrate is demonstrated. The output voltage of the TE generator is determined to be similar to 4.3 mV from a temperature difference of 50 K.