H. Tang, X. Wang, Y. Xiong, Y. Zhao, Y. Zhang, Y. Zhang, J. Yang*, and D. Xu*, Nanoscale 7, 6683-6690 (2015).
Bismuth selenide (Bi2Se3) nanoribbons attracted tremendous research interests recently to study the property of topologically protected surface states that enable new opportunities to enhance thermoelectric performance. However, thermoelectric characterization of individual Bi2Se3 nanoribbons is rare due to the technological challenges in the measurement. One challenge is to ensure good contacts between the nanoribbon and electrodes in order to determine thermal and electrical properties accurately. In this work, we report on thermoelectric characterization of individual Bi2Se3 nanoribbons via a suspended microdevice method. Through careful measurements, we demonstrated that contact thermal resistance is negligible after the electron-beam-induced deposition (EBID) of platinum/carbon (Pt/C) composites at the contacts between the nanoribbon and electrodes. It is shown that thermal conductivity of Bi2Se3 nanoribbons is less than 50% of the bulk value in the whole measurement temperature range, which can be attributed to the enhanced phonon boundary scattering. Our results indicate that intrinsic Bi2Se3 nanoribbons are highly doped n-type semiconductors, therefore, the Fermi level should be in the conduction band and no topological transport behaviors can be observed in the intrinsic system.