Large thermoelectric figure-of-merits from SiGe nanowires by simultaneously measuring electrical and thermal transport properties

Eun Kyung Lee, Liang Yin, Yongjin Lee, Jong Woon Lee, Sang Jin Lee, Junho Lee, Seung Nam Cha, Dongmok Whang, Gyeong S. Hwang, Kedar Hippalgaonkar, Arun Majumdar, Choongho Yu, Byoung Lyong Choi, Jong Min Kim, Kinam Kim

Research output: Contribution to journalArticlepeer-review

178 Scopus citations

Abstract

The strongly correlated thermoelectric properties have been a major hurdle for high-performance thermoelectric energy conversion. One possible approach to avoid such correlation is to suppress phonon transport by scattering at the surface of confined nanowire structures. However, phonon characteristic lengths are broad in crystalline solids, which makes nanowires insufficient to fully suppress heat transport. Here, we employed Si-Ge alloy as well as nanowire structures to maximize the depletion of heat-carrying phonons. This results in a thermal conductivity as low as ∼1.2 W/m-K at 450 K, showing a large thermoelectric figure-of-merit (ZT) of ∼0.46 compared with those of SiGe bulks and even ZT over 2 at 800 K theoretically. All thermoelectric properties were "simultaneously" measured from the same nanowires to facilitate accurate ZT measurements. The surface-boundary scattering is prominent when the nanowire diameter is over ∼100 nm, whereas alloying plays a more important role in suppressing phonon transport for smaller ones.

Original languageEnglish
Pages (from-to)2918-2923
Number of pages6
JournalNano Letters
Volume12
Issue number6
DOIs
StatePublished - 13 Jun 2012

Keywords

  • Simultaneous measurement
  • alloy scattering
  • boundary scattering
  • thermal conductivity reduction

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