Elastic Measurements of Amorphous Silicon Films at mK Temperatures
Elastic Measurements of Amorphous Silicon Films at mK Temperatures
复制标题
mK 温度下非晶硅薄膜的弹性测量
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
G. Jernigan
中科院分区：
文献类型：
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作者：
A. Fefferman;A. Maldonado;E. Collin;Xiao Liu;T. Metcalf;G. 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 $$Q^{-1}$$Q-1 near 1 K. The only known exceptions to this universality are the $$Q^{-1}$$Q-1 of certain thin films of amorphous silicon, carbon and germanium. Recently, it was found that $$Q^{-1}$$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 $$Q^{-1}$$Q-1 at 1 K implies a reduction in $$P_{0}\gamma ^{2}$$P0γ2, where $$P_{0}$$P0 is the density of TLSs and $$\gamma $$γ 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 $$P_{0}$$P0 or $$\gamma $$γ is responsible for the reduction in $$Q^{-1}$$Q-1 with deposition temperature.
