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TT: Fachverband Tiefe Temperaturen
TT 11: Poster Session: Matter at Low Temperature
TT 11.4: Poster
Monday, March 14, 2011, 14:00–18:00, P4
Mechanical dissipation in bulk silicon for precision measurements — •Gerd Hofmann1, Christian Schwarz1, Julius Komma1, Daniel Heinert1, Ronny Nawrodt1, Giles Hammond2, Alexander Grib3, and Paul Seidel1 — 1Friedrich-Schiller-Universität Jena, Institute for Solid State Physics, Helmholtzweg 5, D-07743 Jena, Germany — 2University of Glasgow, Institute for Gravitational Research, Kelvinbuilding, University Avenue, G12 8QQ Glasgow, Scotland — 3Kharkov National University, Physics Department, 61077 Kharkov, Ukraine
Low mechanical loss materials are of great interest in high precision lengths measurements like interferometric gravitational wave detectors or cavities for laser stabilisation. The Brownian thermal noise of a test mass is directly linked to its mechanical loss by means of the fluctuation dissipation theorem.
We present systematic loss measurements of silicon bulk materials in a temperature range from 5 to 300 K and a frequency range from 10 to 100 kHz. The mechanical loss is obtained at the resonance frequencies by a Q-factor measurement. Dissipation processes that cause the mechanical loss like thermo-elastic damping or impurity based damping in the silicon samples are discussed in detail. Especially, the influence of oxygen impurities introduced during crystal growth on the mechanical loss is discussed. A strong dissipation peak at around 113 K is linked directly to transitions within a siloxane complexe (Si-O-Si). Mechanical losses as low as 2×10−9 have been obtained around 5.6 K.
This work is supported by the DFG under contract SFB TR7.