Nanostructured materials behave dramatically different from their bulk counterpart in both electronic properties as well as thermal transport properties. With the immerging low dimensional materials such as nanowires or two-dimensional materials, the research interest has been focused on nanoengineering these materials for different applications including high-performance thermoelectric generator and effective thermal management. On the other hand, these newly developed material systems also arises new scientific questions and offers great opportunities to fundamentally understand the transport physics in nanostructures.

In this work, we would like to present two examples of nanoengineering low dimensional materials to modify their thermoelectric and thermal transport properties which addresses both graphene and semiconductor superlattice nanowires respectively. It is well known that graphene is an excellent candidate electronic material due to its high carrier mobility as well as it is ultrahigh thermal conductivity. Notably, with high thermal conductivity, the thermal management in graphene-based electronic circuit is considered a superior to silicon-based devices. However, this conclusion is based on previous studies on the pristine graphene sheet instead of nanopatterned graphene. We studied the thermal transport behavior of graphene nanomesh with high-density nanoholes and discovered the substantial thermal conductivity suppression with the introduced patterns. This study highlighted the importance of the phonon backscattering inside the two-dimensional graphene system and the thermal management may be more difficult than previously estimated in graphene electronics.

On the other hand, while the thermal conductivity reduction in nanoengineered materials has been demonstrated in many studies, the Seebeck enhancement in nanomaterials was seldom observed. Previously, it has been predicted that the energy filtering effect in superlattice materials may induce an enhanced Seebeck coefficient in nanomaterials. However, since the superlattice materials is usually prepared by high-cost vapor-phase method which cannot be applied to large-scale application. Here, we harnessed the lattice strain of the epitaxy junctions and developed a solution based chemical synthesis method to prepare superlattice nanowires. We compared the Seebeck coefficient and electrical conductivity of the superlattice nanowire which demonstrated energy filter effect and enhanced thermoelectric properties.

Reference:

1. Z. Xiong, X. Wang, H. K. Lee, J. Zhan, Y. Chen, J. Tang, Thermal Transport in Supported Graphene Nanomesh. ACS Appl. Mater. Interfaces Article ASAP (2018)
2. Z. Xiong, Y. Cai, X. Ren, B. Cao, J. Liu, Z. Huo, J. Tang, Solution-Processed CdS/Cu2S Superlattice Nanowire with Enhanced Thermoelectric Property. ACS Appl. Mater. Interfaces 9 (38), 32424 (2017)