Bi2Te3 Nanoplates' Selective Growth Morphology on Different Interfaces for Enhancing Thermoelectric Properties

Bi2Te3, a typical thermoelectric (TE) material as well as topological insulator, exhibits anisotropy characteristics due to its layered structure. (00l)-oriented Bi2Te3 reported with good TE properties in the ab-plane is not the best choice for "pi"-type nanomicro TE devices. Bi2Te3 nanoplates' growth behavior as well as their corresponding TE properties were modulated on different substrates (Si(111), H-terminated Si(111), and glass) by molecular beam epitaxy in this paper. The interfaces between Bi2Te3 and substrate play an important role in Bi2Te3 nanoplates' morphology, along with the related TE properties. The intersected nanoplates, which possess higher density grain boundaries compared with the stacked ones, filter the low-energy carriers and enhance phonon scattering. Thus, an increased Seebeck coefficient and predictable reduction of thermal conductivity were achieved by using intersected nanoplates. Moreover, the ratio of intersected/stacked Bi2Te3 nanoplates as well as their size can be properly controlled by modulating the substrates' surface and seed layer which can be same applied to other layered materials. This study is conducive to realizing the integration of two-dimensional layered materials in micro-/nanodevices by controlling the specific growth behavior and properties.