Journal of Low Temperature Physics

, Volume 187, Issue 5–6, pp 654–660 | Cite as

Elastic Measurements of Amorphous Silicon Films at mK Temperatures

  • Andrew Fefferman
  • Ana Maldonado
  • Eddy Collin
  • Xiao Liu
  • Tom Metcalf
  • Glenn Jernigan


The low-temperature properties of glass are distinct from those of crystals due to the presence of poorly understood low-energy excitations. The tunneling model proposes that these are atoms tunneling between nearby equilibria, forming tunneling two-level systems (TLSs). This model is rather successful, but it does not explain the remarkably universal value of the mechanical dissipation \(Q^{-1}\) near 1 K. The only known exceptions to this universality are the \(Q^{-1}\) of certain thin films of amorphous silicon, carbon and germanium. Recently, it was found that \(Q^{-1}\) of amorphous silicon (a-Si) films can be reduced by two orders of magnitude by increasing the temperature of the substrate during deposition. According to the tunneling model, the reduction in \(Q^{-1}\) at 1 K implies a reduction in \(P_{0}\gamma ^{2}\), where \(P_{0}\) is the density of TLSs and \(\gamma \) is their coupling to phonons. In this preliminary report, we demonstrate elastic measurements of a-Si films down to 20 mK. This will allow us, in future work, to determine whether \(P_{0}\) or \(\gamma \) is responsible for the reduction in \(Q^{-1}\) with deposition temperature.


Glass Tunneling two-level systems Elasticity Vapor-deposited glass 



We acknowledge support from the ERC CoG Grant ULT-NEMS No. 647917 and from the US Office of Naval Research.


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Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  • Andrew Fefferman
    • 1
  • Ana Maldonado
    • 1
  • Eddy Collin
    • 1
  • Xiao Liu
    • 2
  • Tom Metcalf
    • 2
  • Glenn Jernigan
    • 2
  1. 1.Institut NéelCNRS and Université Grenoble AlpesGrenobleFrance
  2. 2.Naval Research LaboratoryWashingtonUSA

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