Nawroth, R.R.NawrothSchwarz, C.C.SchwarzKroker, S.S.KrokerMartin, I.W.I.W.MartinBrückner, F.F.BrücknerCunningham, L.L.CunninghamGroße, V.V.GroßeGrib, A.A.GribHeinert, D.D.HeinertHough, J.J.HoughKäsebier, T.T.KäsebierKley, E.B.E.B.KleyNeubert, R.R.NeubertReid, S.S.ReidRowan, S.S.RowanSeidel, P.P.SeidelThürk, M.M.ThürkTünnermann, A.A.Tünnermann2022-03-152022-03-152010https://publica.fraunhofer.de/handle/publica/413777The investigation of the mechanical loss of different silicon flexures in a temperature region from 5 to 300K is presented. The flexures have been prepared by different fabrication techniques. A lowest mechanical loss of 3×10 to -8 was observed for a 130 µm thick flexure at around 10K. While the mechanical loss follows the thermoelastic predictions down to 50K a difference can be observed at lower temperatures for different surface treatments. This surface loss will be limiting for all applications using silicon based oscillators at low temperatures. The extraction of a surface loss parameter using different results from our measurements and other references is presented. We focused on structures that are relevant for gravitational wave detectors. The surface loss parameter s = 0.5 pm was obtained. This reveals that the surface loss of silicon is significantly lower than the surface loss of fused silica.en620paper