Spectral phonon scattering from sub-10 nm surface roughness wavelengths in metal-assisted chemically etched Si nanowires

M. G. Ghossoub, K. V. Valavala, M. Seong, B. Azeredo, Keng Hao Hsu, J. S. Sadhu, P. K. Singh, S. Sinha

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

Frequency dependence in phonon surface scattering is a debated topic in fundamental phonon physics. Recent experiments and theory suggest such a phenomenon, but an independent agreement between the two remains elusive. We report low-temperature dependence of thermal conductivity in silicon nanowires fabricated using a two-step, metal-assisted chemical etch. By reducing etch rates down to 0.5 nm/s from the typical >100 nm/s, we report controllable roughening of nanowire surfaces and selectively focus on moderate roughness scales rather than the extreme scales investigated previously. This critically enables direct comparison with perturbation-based spectral scattering theory. Using experimentally characterized surface roughness, we show that a multiple scattering theory provides excellent agreement and explanation of the observed low-temperature dependence of rough surface nanowires. The theory does not employ any fitting parameters. A 5-10 nm roughness correlation length is typical in metal-assisted chemical etching and resonantly scatters dominant phonons in silicon, leading to the observed ∼T1.6-2.4 behavior. Our work provides fundamental and quantitative insight into spectral phonon scattering from rough surfaces. This advances applications of nanowires in thermoelectric energy conversion.

Original languageEnglish (US)
Pages (from-to)1564-1571
Number of pages8
JournalNano Letters
Volume13
Issue number4
DOIs
StatePublished - Apr 10 2013
Externally publishedYes

Keywords

  • Silicon nanowire
  • frequency dependence
  • phonon
  • surface scattering
  • thermal conductivity

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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