Self-assembled bismuth telluride films with well-aligned zero- to three-dimensional nanoblocks for thermoelectric applications

Abstract

The dimension and size of the building blocks as well as the preferential orientation, geometry and regularity of their assemblies are the most important key factors for fabricating thermoelectric materials with a high figure-of-merit (ZT) which is governed by the efficiencies in transporting electrical and thermal energies along the measurement direction. A one-step and large-area growth approach has been successfully developed employing pulsed laser deposition (PLD) for producing physically self-assembled and well-aligned Bi2Te3 nanostructures on SiO2/Si substrates without pre-built templates or catalysts. The precisely parameter-controlled growth provides four highly reproducible and significant Bi2Te3 assemblies, comprising 0-dimensional (0-D) nanoparticles, 1-D nanorods, 2-D nanoflakes, and 3-D nanocanyons, respectively exhibiting an overall (006), (015), (110), and (006) preferential orientation normal to the substrate surface. The nanoparticle assisted crystal growth is proposed, mainly involving the condensation of the plasma species in the gas phase at higher ambient pressures and the following diffusion and reorganization of the deposited nanoparticle atoms on the substrates. The well-aligned 0-D to 3-D Bi2Te3 nanostructures show more excellent in-plane power factors than most of the randomly aligned Bi2Te3 nanostructures at room temperature mainly due to significantly reducing inter resistance. The thermoelectric properties of these well-aligned Bi2Te3 nanostructures are comparable to any other intrinsic Bi2Te3 nanostructures that have ever been reported. The present data are valuable for further improving and designing advanced thermoelectric materials and confirm that precise control of nanostructural aggregation is an effective strategy for enhancing the thermoelectric performance.