奈米工程與微系統研究所　書報討論

Seminar of Inst. NanoEngineering and MicroSystems

Associate Prof. Masahiro NOMURA, Ph.D.

Institute of Industrial Science,

The University of Tokyo.

E-mail: nomura@iis.u-tokyo.ac.jp

Advanced heat conduction engineering by phonon engineering and thermoelectric application

Abstract

Thermal phonon engineering using ballisticity and wave nature of phonons brought new possibility to thermal conduction engineering. We introduce characteristic heat transfer in Si phononic nanostructures including heat focusing [1] and counter intuitive heat transfer based on wave nature of phonons [2].

We fabricated 145-nm-thick single-crystalline Si porous membranes by conventional top-down approach using electron beam lithography and measured thermal conduction in the nanostructures by a custom built micro-time-domain thermoreflectance system. We demonstrate that heat flow can be focused by using the ballisticity of thermal phonons within the mean free path: heat flux can be focused in a phononic structure with holes which aligned in a radial fashion. The fabricated structures have a slit centered at the focus or shifted. The heat dissipation times were compared among these structures and showed strong position dependence of the slit; the fastest heat dissipation was observed when the slit was located at the focus. About 7% difference can be observed even at room temperature due to long thermal phonon MFP is Si. This result is the first demonstration of heat focusing using tailored phononic structures. In the presentation, development of nanostructured Si thermoelectric material will be also presented.

Key words: phonon engineering, phononics, phonic crystal, phonon, heat transport

[1] R. Anufriev, A. Ramiere, J. Maire, and M. Nomura, Nature Communications 8, 15505 (2017).

[2] J. Maire, R. Anufriev, A. Ramiere, R. Yanagisawa, S. Volz, and M. Nomura, Science Advances 3, e1700027 (2017).

15:30-17:20 on Oct. 22 (Mon), 2018 in Room 108 of Eng. Building I

Host：Prof. Da-Jeng Yao  djyao@mx.nthu.edu.tw Ext: 42850

Contact：黃微稜 hwleng@mx.nthu.edu.tw  Ext: 33737

TA：李志恩 c27180339@gmail.com