Thermal conductivity can be tuned as one degree of freedom to improve a material’s performance in many energy-related applications. For thermoelectric (TE) materials, a low lattice thermal conductivity is preferred for a higher energy conversion efficiency or better TE cooling performance. The phonon transport in a material can be manipulated by introducing nano-sized structures such as interfaces and porosity. In the 1st part of this talk, a Si/Ge heterojunction formed by film-wafer bonding is studied for its interfacial thermal resistance. The study reveals the important role of an alloy-like interfacial layer to heat transport across the heterojunction. In the 2nd topic, thermal properties of the nanoporous Si thin film are studied. The proposed nanoslot structure is effective in suppressing the in-plane direction phonon transport. Such structure also shows an extremely high convective heat transfer coefficient, which could be useful for thermal regulation or other applications in the gas environment.
Sien Wang is a Ph.D. student of the Department of Aerospace and Mechanical Engineering at the University of Arizona. He received his B.S degree from Shanghai Jiao Tong University, China in 2017. His research interests include the characterization of thermal and electrical properties of nanostructured thin films and 2D materials.