Investigation of mechanical losses of thin silicon flexures at low temperatures
cond-mat.mtrl-sci
/ Authors
R. Nawrodt, C. Schwarz, S. Kroker, I. W. Martin, F. Brückner, L. Cunningham, V. Große, A. Grib, D. Heinert, J. Hough
and 8 more authors
T. Käsebier, E. B. Kley, R. Neubert, S. Reid, S. Rowan, P. Seidel, M. Thürk, A. Tünnermann
/ Abstract
The investigation of the mechanical loss of different silicon flexures in a temperature region from 5 to 300 K is presented. The flexures have been prepared by different fabrication techniques. A lowest mechanical loss of $3\times10^{-8}$ was observed for a 130 $μ$m thick flexure at around 10 K. While the mechanical loss follows the thermoelastic predictions down to 50 K 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 $α_s$ = 0.5 pm was obtained. This reveals that the surface loss of silicon is significantly lower than the surface loss of fused silica.