LAUSR

Abstract As a topological insulator with metallic-conduction surface states, nanostructured Bi2Te3 has attracted intense attention for thermal and electronic applications. A critical challenge is to reveal the underlying mechanism between dimension symmetry and phonon scattering, especially in two-dimensional Bi2Te3 nanostructures. In this paper, we report a simple hydrothermal method to produce pure two-dimensional Bi2Te3 nanofilms with controllable morphology and thickness. We further investigated how the Raman vibrational modes depend on the two different morphologies of Bi2Te3: nanoplatelets and nanosheets. The results show that out-of-plane Ag modes are more significantly suppressed in single-crystal Bi2Te3 nanoplatelets with a few quintuple layers. A new Raman peak around 71 cm−1 appears, which corresponds to the infrared-active Eu1 mode. The infrared-active mode Au1 undergoes a significant shift, which is indicative of morphology-dependent features on the nanoplatelets and nanosheets. The difference is extensively explored by group theory analysis. In addition, the basal in-plane vibrational mode Eg2 redshifts significantly, suggesting that the quantum confinement effect could affect nanoplatelets interface interactions between layers. Furthermore, the transport measurements of pressed bulk samples formed by the two different morphologies of Bi2Te3 nanofilms were also compared. The nanoplatelets performed an enhancement of Seebeck coefficient and a reduction of thermal conductivity with enhanced scattering at grain boundaries and out-of-plane vibrate suppressed.