High In-Plane Seebeck Coefficients of Bi–Sb–Te Alloy Thin Films with Growth Texture and Their Field-Controlled Seebeck Coefficients

Bismuth antimony telluride (Bi_xSb_2–xTe₃, BST) is an alloy that has widely been used over the past 5 decades for excellent p-type thermoelectric (TE) materials that operate around 300 K, for example, for electronic refrigeration and generators with other n-type TE materials, including Bi₂Te₃ alloy materials. However, despite significant progress in bulk materials, there has been less progress and less detailed TE information on Seebeck coefficients in the thin-film form. Here, we report reliable in-plane Seebeck coefficients of p-type Bi_0.5Sb_1.5Te₃ (BST) films and Bi₂Te₃/Bi_0.5Sb_1.5Te₃ (BT/BST) multilayer films at 300 K using a promising measurement technique with a precisely controlled temperature difference and excellent linearity. Due to the growth texture of the films, a high in-plane Seebeck coefficient of ∼298 μV/K was achieved in 100 nm thick BST films at 300 K, which is an increase of ∼224% compared to that in 200 nm thick BT/BST multilayer films. Moreover, we demonstrate field-controlled Seebeck coefficients of p-BST films by a backside gate configuration in a field-effect transistor. Our results demonstrate the importance of providing a promising measurement technique and reliable information on the in-plane Seebeck coefficients of Bi–Sb–Te alloy thin films for further TE device applications.