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Investigation of mechanical losses of thin silicon flexures at low temperatures

: Nawrodt, R.; Schwarz, C.; Kroker, S.; Martin, I.W.; Bassiri, R.; Brückner, F.; Cunningham, L.; Hammond, G.D.; Heinert, D.; Hough, J.; Käsebier, T.; Kley, E.-B.; Neubert, R.; Reid, S.; Rowan, S.; Seidel, P.; Tünnermann, A.


Classical and quantum gravity 30 (2013), No.11, Art. 115008, 12 pp.
ISSN: 0264-9381
ISSN: 1361-6382
Journal Article
Fraunhofer IOF ()

Studies of the mechanical loss of silicon flexures in a temperature region from 5 to 300 K are presented, where the flexures have been prepared by different fabrication techniques of interest for the construction of suspension elements of future interferometric gravitational wave detectors. A lowest mechanical loss of 3 × 10(exp -8) was observed for a 130 m thick flexure at around 10 K. While the mechanical loss follows the thermo-elastic predictions down to 50 K, at lower temperatures the observed loss is found to be a function of surface roughness. This surface loss is of interest for all applications using silicon-based oscillators at low temperatures. The extraction of a surface loss parameter using results from our measurements and those of other authors is presented and the relevance for future gravitational wave detector suspensions is discussed. A surface loss parameter alpha (ind s) = 0.5 pm was obtained. This reveals that the surface loss of silicon is significantly lower than the surface loss of fused silica.